high-performance aromatic polyamides

Progress in Polymer Science 35 (2010) 623686

Contents lists available at ScienceDirect

Progress in Polymer Science

journa l homepage: www.e lsev ier .com/ locate /ppolysc i

High-p

Jos M. GDepartamento

a r t i c l

Article history:Received 28 JuReceived in reAccepted 15 SAvailable onlin

Keywords:Aromatic polyAramidsHigh-performance polymers with applications in the aerospace and armament industry, bullet-proof body armor, pro-

tective clothing, sport fabrics, electrical insulation, asbestos substitutes, and industriallters, among others. Owing to their chemical structure, they exhibit extremely high tran-sition temperatures that lie above their decomposition temperatures, are sparingly soluble

Contents

1. Introd2. Comm3. Arom

3.1.3.2.3.3.

4. Polya4.1.4.2.4.3.

5. Expan5.1.

CorresponE-mail addURL:http:

0079-6700/$ doi:10.1016/j.in common organic solvents and, accordingly, can only be transformed upon solution.Researchefforts are thereforeunderway to take advantageof their properties, enhance theirprocessability andsolubility, and incorporatenewchemical functionalities in thepolyamidebackbone or lateral structure, so that their applicability is expanded and remains on theforefront of scientic research.

2009 Elsevier Ltd. All rights reserved.

uction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624ercial aromatic polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624

atic polyamide synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625Low-temperature solution methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625High-temperature solution methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627Alternative polymerization methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627

mides with controlled structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627Chain-growth polycondensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628Constitutional isomerism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 630Spherical-like aromatic polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631ding the applications of the aromatic polyamides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632Polyamides with specialty properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6325.1.1. Optically active polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6325.1.2. Luminescent and electrochromic polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

ding author. Tel.: +34 947 258 085; fax: +34 947 258 831.ress: [email protected] (J.M. Garca).//www2.ubu.es/quim/quimorg/polimeros/polimeros.htm (J.M. Garca).

see front matter 2009 Elsevier Ltd. All rights reserved.progpolymsci.2009.09.002erformance aromatic polyamides

arca , Flix C. Garca, Felipe Serna, Jos L. de la Penade Qumica, Facultad de Ciencias, Universidad de Burgos, Plaza de Misael Banuelos s/n, 09001 Burgos, Spain

e i n f o

ly 2009vised form 9 September 2009eptember 2009e 25 September 2009

amides

a b s t r a c t

Wholly aromatic polyamides (aramids) are considered to be high-performance organicmaterials due to their outstanding thermal andmechanical resistance. Theirproperties arisefromtheir aromatic structure andamide linkages,which result in stiff rod-likemacromolec-ular chains that interact with each other via strong and highly directional hydrogen bonds.These bonds create effective crystallinemicrodomains, resulting in a high-level intermolec-ularpackingandcohesiveenergy. Thebetterknowncommercial aramids, poly(p-phenyleneterephthalamide) and poly(m-phenylene isophthalamide), are used in advanced technolo-gies and have been transformed into high-strength and ame resistant bers and coatings,

624 J.M. Garca et al. / Progress in Polymer Science 35 (2010) 623686

5.1.3. Polyamides in membrane technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6435.1.4. Polyamides with selective receptors and environmental applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6465.1.5. Polyamides with outstanding mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647

5.2. Selected polyamide structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . .. . . . . . .. . . . . . . .. . . . . . . .. . . . . . . .. . . . . . .

. . . . . . . .6. Solub . . . . . . .

Ackno . . . . . . . .Refer . . . . . . .

1. Introdu

High-peby specic cresistance asity, high cinsulation p

AccordinHPM due toerties, whicThey are geous replaused goodsapplication

The eararamids (thpoly(p-phephenyleneformed upcut-resistanthey can beproperties.advanced faites in the asubstitutesindustrial others.

Howevethe commesition temporganic solvtheir applic

As a conhas focusedbility in orapplicationresearch effperformancelectro- orgas or ionmaterials,mechanical

This woand possibl

d polyast deork inlso cocationns ofamide

mme

hollyich ato aro

of the poly(merciaof the.e rstp-bene marar. Teraturand p

amideced byPPPT iformein cone higits ch5.2.1. Polyamides with heterocyclic rings in the main chain .5.2.2. Polyamides with heteroaromatic pendant rings . . . . . . .5.2.3. Cardo polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.2.4. Fluorinated and chlorinated polyamides. . . . . . . . . . . . . . .5.2.5. Crown ether containing polyamides . . . . . . . . . . . . . . . . . . .5.2.6. Polyamides with bulky pendant structures . . . . . . . . . . . .5.2.7. Segmented block polyamides . . . . . . . . . . . . . . . . . . . . . . . . . . .5.2.8. Unclassied polyamide structures . . . . . . . . . . . . . . . . . . . . .

le polyamides. Polyamides with improved transformability . . . . . .wledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ction

rformance materials (HPM) are characterizedriteria, such as possessing outstanding thermalnd/or mechanical strength, low specic den-onductivity, high thermal, electrical, or soundroperties, or superior ame resistance.gly, aromatic polyamides are considered to betheir superior thermal and mechanical prop-

h make them useful for advanced technologies.nding increasing demand for use as advanta-cements for metals or ceramics in currently

, or even as newmaterials in novel technologicals [14].liest, simplest, and best known commerciale shortened form of aromatic polyamides) arenylene terephthalamide) (PPPT) and poly(m-isophthalamide) (PMPI). Both can be trans-on solution by wet spinning into ame,t, and high tensile strength synthetic bers, orcast into varnishes or enamels yielding similarThe transformed materials have applications inbrics, coatings, andllers, as advancedcompos-erospace and armament industry, as asbestos

, electrical insulation, bullet-proof body armor,lters, and protective and sport clothing, among

r, the extremelyhigh transition temperatures ofrcial aramids, which lie above their decompo-eratures, and their poor solubility in commonentsgive rise toprocessingdifculties and limit

relatethe ping ware aapplicatiopoly(

2. Co

Win whto twturethe pcommsomeyears

Thpoly(on thKevltemp(TPC)phorreplatem.transtions

Thfromations.sequence, recent basic and applied researchon enhancing their processability and solu-

der to broaden the scope of the technologicals of these materials. There is currently a hugeort directed toward exploiting the special high-e characteristics of the polyamides to obtainphotoluminescent materials, reverse osmosis,-exchange membranes, optically active (OA)nanocomposites, etc. with superior thermo-performances.rk sets out to review the design, preparation,e applications of new aromatic polyamides and

ture withmacromolehigh crystaintramolecuformed intthermal an

Taking twith all-mePMPI, havetion in itsThus, PMPthermal andnative to PP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681

mers by reviewing the relevant literature fromcade. A few papers on the very rst pioneer-this area and some other select publications

nsidered. A recent look at patented industrialdevelopments and expected commercial appli-aromatic and semiaromatic polyamides, andimide)s, has been recently published [5].

rcial aromatic polyamides

aromatic polyamides are synthetic polyamidesleast 85% of amide groups are bound directlymatic rings [2]. Scheme 1 shows the struc-oly(p-phenylene terephthalamide) (PPPT) and

-phenylene isophthalamide) (PMPI), which arel aramids of great economic relevance, andtrade names they have used over the last 40

commercialized all-para oriented aramid waszamide) (PPBA) (Fiber B). PPBA was replacedket by PPPT in 1970 under the tradename ofheir polycondensation was performed at lowes in a solution of terephthaloyl dichloride-phenylenediamine (PPD) in hexamethylphos-(HMPA). Later, the solvent was successfullyan N-methyl-2-pyrrolidone (NMP)/CaCl2 sys-

s even more insoluble than PPBA and must bed into bers by spinning from lyotropic solu-centrated sulfuric acid at high temperatures.h-performance properties of the PPPT resultemical structure. The wholly aromatic struc-

all-para substitutions creates stiff rod-likecules, having a high cohesive energy and allization tendency due to the very favorablelar hydrogen bonds. PPPT bers can be trans-

o materials and composites having superiord mechanical resistance.his into account, wholly aromatic polyamidesta orientation in the phenylene ring, such asless linear structures and a concomitant reduc-cohesive energy and crystallization tendency.I is a high-performance polymer, with highmechanical resistances. PMPI is a viable alter-

PT, only slightly underperforming it. It was rst

J.M. Garca et al. / Progress in Polymer Science 35 (2010) 623686 625

Nomenclature

AFM atomic force microscopyBOC t-butoxycarbonyl groupCE coloration efciencycr char yieldDBTL dibutyltin dilaurateDMA N,N-dimethylacetamideDMF N,N-dimethylformamideDMTA dynamic mechanical thermal analysisDSC differential scanning calorimetryEC electrochromismEDG electron donating groupEL electroluminescenceEWG electron-withdrawing groupGC gas chromatographyGPC gel permeation chromatographyHMPA hexamethylphosphoramideHPM high-performance materialsie inductive effectIPC isophthaloyl dichlorideLC liquid crystalLOI limiting oxygen indexMn, Mw number-average and weight-average

molecular weight, measured by GPS usingPS standars unless otherwise indicated

MPD m-phenylenediamineMW microwave radiationNMP N-methyl-2-pyrrolidoneOA optically activeOAP optically active polymerODA 3,4-diaminodiphenyl etherODA/PPPT co-poly-(p-phenylene/3,4-

oxydiphenylene terephthalamide)OLEDs organic light-emitting diodesPAIs poly(amide imide)sPAs polyamidesPEG poly(ethylene glycol)PL photoluminescencePLEDs polymer light-emitting diodesPMPI poly(m-phenylene isophthalamide)PPD p-phenylenediaminePPPT poly(p-phenylene terephthalamide)QSPR quantitative structureproperty relation-

shipre resonance effectRO reverse osmosisrt room temperatureTd degradation temperature (onset, measured

by TGA)Td5; Td10 decomposition temperature at 5% and 10%

weight loss (measured by TGA)TEA triethylamineTFA triuoroacetic acidTg glass-transition temperature (measured by

DSC unless otherwise indicated)TGA thermogravimetric analysisTHF tetrahydrofuran

Tm melting temperature (measured by DSCunless otherwise indicated)

TMC trimesoyl chlorideTPCTPPTs

described bunder the t

Moreove3,4-diaminsoluble polunder the tmetry of thrise to a les

The phybers (crysmoisture covated tempresistance)lms and pOzawa andTable 1 dep

Considechemicallyefforts arecohesive eto their extthermal trperformancapplicationpromising anescent, ionmaterials.

3. Aromat

3.1. Low-te

The mosmatic polywith diamisation reacdiamines ataprotic solvdimethylacLiCl, CaCl2,ity promotegroups, dimgen bonds.

PPPT antively, arep-phenylen(TPC), or mdichloride (ionic compogenerally pily obtainedterephthaloyl dichloridetriphenylphosphitesoftening temperatures

y Du Pont in 1961 and commercialized in 1967,rademark Nomex.r, the copolymerization of TPC with PPD andodiphenyl ether (ODA) gives rise to a relativelyymer, ODA/PPPT (Scheme 1), commercializedradename of Technora since 1987. The asym-e monomer ODA and the copolymerization gives ordered material with lower cohesive energy.sical characteristics of the commercial aramidtal lattice parameters, density, equilibriumntent, tensile properties at room and at ele-eratures, thermal properties and chemicaland the properties of the commercial aramidapers were well summarized by Gallini [6],Matsuda [7], Tanner et al. [8] and Yarn [9].

icts a summary of these properties.ring the extraordinary characteristics of thesimplest aramids, PPPT and PMPI, the researchtwofold directed: (a) the diminishing of thenergy that causes intractable materials dueremely low solubility and exceptionally highansitions with little change to their high-e properties and (b) the expansion of theirs as high-performance materials in new anddvanced elds, such as optically active, lumi-ic exchange, ame resistant and ber-forming

ic polyamide synthesis

mperature solution methods

t common methods for the preparation of aro-amides are the reaction of diacid dichloridesnes at low temperatures or direct conden-tions in solution of aromatic diacids withhigh temperatures. The solvents used are polarents like N,N-dimethylformamide (DMF), N,N-etamide (DMA), NMP, and HMPA. Salts, such asor a mixture of both, are often used as solubil-rs because the cations interact with the amideinishing the strength of the interchain hydro-

d PMPI, or Kevlar and Nomex, respec-prepared commercially by condensation of

ediamine (PPD) and terephthaloyl dichloride-phenylenediamine (MPD) and isophthaloylIPC) using NMP as the solvent and CaCl2 as thenent. The low temperature solution method is

referred when the diacid chloride can be eas-from the corresponding aromatic diacid. On


the other hamercially bwith TPC. Tcopolymerilower cohein NMP, wneutralizatible viscousmain drawdensation tbe employmaterials. T

atic poh is trsityximatearereightsic visMarkcomm

Table 1Properties of c

Property

Density (g/cWater uptak

Thermal proTg (C)Tm (C)Td (C, in N

Tensile propStrength (Modulus (Elongation

Crystallinity

Flammabilit

a Decomposb The compa

lms obtainedScheme 1.

nd, ODA/PPPT, or Technora, is prepared com-y condensation of PPD and ODA (50% each)he asymmetry of the monomer ODA and thezation give rise to a less ordered material withsive energy. Thus, the polymer is preparedithout solubility promoters (salts), and uponon of the evolved HCl with Ca(OH)2, the sta-isotropic solution if suitable for spinning. Theback of this method is related to the polycon-

aromwhicdispeapproand nular wintrincalledof theheory; extremely high monomer purity musted in order to obtain high molecular weighthe number-average molecular weight (Mn) of

review of GA modi

tion of the

ommercial aromatic polyamide bers.

Polymer

PMPI PPPT

m3) 1.38 1.44e (%), at 65% RH 5.2 3.9

perties275 365 da >500 da

2) 400430 520540

ertiesb

GPa) 0.590.86 2.93.0GPa) 7.912.1 70112(%) 2045 2.43.6

Highly crystalline (6895%) Highly crystalline

y (L.O.I.) 29 29

es (d).rison of themechanical properties of oriented berswith the properties reportedby casting, is not usually straightforward.lyamides generally range (1030)103 g/mol,ypical of condensation polymers. The poly-of the polymers obtained by this method isely two for lower molecular weight polymersthree for polymerswithweight-averagemolec-s (Mw) >35103 g/mol [6]. The relation of thecosity of the aramids with their Mws, the so-Houwink equation, and a deeper descriptionercial preparationmethods can be found in the

allini [6].cation of this method includes the silyla-

diamines to increase the reactivity of the

ODA/PPPT

1.394.0

>500 da

500

3.4724.6

Highly oriented but less crystalline (higher exibilityof the copolymer chain and loose crystalline structure)25

for synthetic polyamides, usually obtained fromunoriented


amino groups. The silylation-polymerization procedureis usually performed in situ to avoid the isolation andpurication of the moisture sensitive silylated diamines[10].

The polyin a two-phcalled interthe acid dica water-imsurfactantmixture ofrise to a poextremely fsolvent sidein the intetion is conon the conthe growinhaving a brosidered tob[12]. Neverttions, in termonomer cpolyamidespared via sthen be cascal propertiused as mosoluble dihpolycondentance.

3.2. High-te

If the diasponding artoo much mcondensatiobeused. Theand it is stillpuritymonside reactioThus, to obcontainingis importanpolymerizaprior prepa

The highmodied bpolycondenconventionchemistry,extremely fthe MW-asto promotediamines uheating syreplaced bytime from 4mers obtainviscosities.

MW has also been used to promote the polycondensa-tion of diacids with aliphatic and aromatic diisocyanates,yielding semiaromatic polyamides and aramids [19]. Thereaction was completed in less than 5min and the

tant p/g.cent eotioneraturic solis a topproaempein theine) chaveighly

h makmidesus, ecliquidt conde usemotetemp

an beng meployihoursical stbtainemolec

lterna

ganicods tos, andmidestheseary o

[3], Seg othhollyred byt polyyl chlof diacines;ion ofalladiudiha

2]; etc

lyam

lyconth pathers eivity onmedicondensation reaction can also be carried outase system at room temperature, via the so-facial polymerization [11]. The diamine andhloride monomers are dissolved in water andmiscible solvent, respectively. A base and aare usually added to the aqueous media. Theimmiscible solutions, upon rapid stirring, giveslymer precipitate in seconds. The reaction isast and occurs in the interphase on the organic. The stoichiometry cannot easily be controlledrphase because the instantaneous concentra-trolled by diffusion and depends only in partcentration of the monomers. Precipitation ofg polymer chains usually produces polymersad molecular weight distribution that are con-eunsuitable forbers orlm-formingmaterialsheless, the tuning of the polymerization condi-ms of the organic solvent type, solvent volume,oncentration, and stirring rate, yields aromaticthat have similar properties than those pre-

olution polycondensation methods. Films cant upon solution, which have desirable chemi-es. Moreover, water insoluble diamines can benomers upon polymerization of their water-ydrochloride derivatives [13]. The interfacialsation has not achieved commercial impor-

mperature solution methods

cid chloride cannot be obtained from the corre-omatic diacid or is of poor quality, i.e., containsoisture sensitive or is heat sensitive, the directn between aromatic diacids and diamines canmethodwasdevelopedbyYamazaki et al. [14],not used for commercial purposes. Again, high-

omers are required andanextra drawback is thens that occur at the high temperatures used.tain an aromatic polyamide with side chainssensitive functional groups by this method, itt to verify the absence of side reactions in thetion conditions. This can be carried out by theration of model compounds.-temperature solution procedure was recentlyy the introduction of microwave-assistedsation. Microwave radiation (MW) is a non-al energy source, now widely used in organicemployed to promote chemical reactions inast and sometimes unconventional ways. Thus,sisted synthesis of polyamides was performed

the condensation of aromatic diacids andnder Yamazaki conditions. The conventionalstem, i.e., temperature control oil bath, isthe MW system, which reduces the reactionh to approximately 2min [1518]. The poly-ed by both methods have comparable inherent

resul0.2 dL

Repromtemporgansionsthis alow-tandpyriduidsare hwhicpolya

Thionicdirecing thto proat lowtion cheatior emfromchemare otheir

3.3. A

Ormethbondpolyaall ofsummFinkAmoning: wprepadirecthiontiondiamreactthe pfrom[31,3

4. Po

PogrowCarotreactsatioolymers had inh values between 0.51 and

fforts have also been directed to the greenerof polycondensation under low- or high-e solution methods. Thus, the replacement ofvents by more environmental friendly ver-pic of current interest in chemistry. Followingch, the mixture of solvents used in the usualrature polycondensation (DMF, DMA, NMP)Yamazaki polyamidation method (NMP and

an be replaced by ionic liquids. The ionic liq-high thermal stability, low vapor pressure,polar, and have a high dielectric constant,es them suitable to dissolve the aromatic.o-friendly aramids have been prepared usings with triphenylphosphite (TPP) to promote theensation of the acid and amide groups, avoid-of harmful solvents like pyridine and NMP, andthe reaction of diacid dichlorides and diamineseratures [2028].Moreover, the polycondensa-carried out by a conventional high-temperaturethod, using TPP as the condensation promoter,ng MW, thus diminishing the reaction timesto minutes. Again, polymers having identicalructures and comparable inherent viscositiesd from both heating methods, suggesting thatular weights are similar.

tive polymerization methods

chemistry provides a wide set of syntheticobtain aromatic or aliphaticaromatic amidesome of them have been used to prepare

. It is beyond the scope of this work to coverprocedures, and we refer the reader to the

f reaction methods found in Gaymans [29],kiguchi and Coutin [30], and Vollbracht [4].er methods not yet described are the follow-and partially aromatic polyamides can also bethe reaction of diacids with diisocyanates; the

condensation of diacids with diamines usingoride as the activating agent; the condensa-ids with the formamidinium salts of aromaticusing diamines or acid-amines and CS2; thearomatic diacid phenyl esters with amines;m-catalyzed carbonylation-polycondensation

loaryl compounds and aromatic diamines.

ides with controlled structure

densation reactions usually follow a step-tern obeying Florys statistical treatment andquation. These theories are based on the equalf the functional groups present in the conden-a. Unequal reactivity ofmonomers arising from


the asymmetry of bifunctional monomers (AA+BB), fromthe control of the reactivity of the functional group of ABmonomers, or from the employment of AxBy monomersproduce polymerswith dened structures that do not obeyconventional polycondensation rules.

4.1. Chain-growth polycondensation

The experimental results in which some high molec-ular weight condensation polymers were obtained withlow conversions opened the way to chain-growth poly-condensation. A good review on the theory, polymerstructures/architectures, and applications of living con-trolled polymerization of condensation polymers waspublished by Yokoyama et al. [33,34].

Thus, the polycondensation of phenyl 4-(octylaminobenzoate) in the presence of the initiator4-nitrobenzoate and a base under mild conditions gives apolymer with a well-dened structure (Scheme 2A). TheMn of the polymer can be controlled up to 22,000 by thefeed ratio of monomer to initiator, was dependent on theconversion, and achieved a polydispersity (Mw/Mn) closeto 1. The base reacts with the AB monomer (2) generatingthe aminyl anion (4), which deactivates the phenyl estermoiety of (2) through the resonance effect (re) by its strongdonating capability (electron donating groupEDG). Onthe other hand, the phenyl ester moiety is strongly acti-vated in the initiator (1) by the electron-withdrawing

(EWG) nitro group. Thus, the initial reaction of the aminylanion (4) with the initiator (1) generates a new weakelectron-withdrawing amide group (5), which facilitatesthe chain growth because the phenyl ester of this chaineasily reacts with the monomer containing the aminylanion (Scheme 2A) [35]. The procedure can be furtherimproved by using the commercial base lithium hexam-ethyldisilazide (LiHMDS) and phenyl 4-methylbenzoateas the initiator (Scheme 2B) [36]. Following the samemethodology, the inductive effect (ie) was exploited toobtain well-dened poly(m-benzamide)s, P3 (Scheme 2C)[3739].

The outstanding mechanical and thermal propertiesof the aromatic polyamides arise from their high cohe-sive energy due to the density, effectiveness, and highlydirectional interchain amideamide hydrogen bonds. TheN-alkyl polyamides are highly soluble because of theabsence of these bonds. In order to obtain aramids (NH)with similar behavior, the amino group can be protectedwith a protecting alkyl group (N-Alkyl), i.e., a benzylgroup that can be easily removed upon treatment of thepolyamide with the proper reagent at mild conditions[40,41].

Living polycondensation allowed the preparation ofblock copolymers, opening new possibilities in the designof materials with a la carte properties. The reaction ofthe initiator with a monomer forms growing polymerchains with an active end group. Thus, the subsequentScheme 2.


Scheme 3.

adding of a proper monomer permits the preparation ofcondensation block copolymers, either parapara blocks(Scheme 3A) [40,41] or metapara blocks [37] (Scheme 3B).The diblock copolymer P4 (Scheme 3) was shown to besoluble in organic solvents, having a narrow molecularweight distribution, and was arranged in a supramolecularself-assembly in THF to give intriguing m-sized bundlesprobably because of the interchain hydrogen bonding ofthe p-benzamide blocks. The authors pointed out that the

self-assembly of block copolymers and star polymers con-taining the well-dened poly(p-benzamide) units wouldbe a useful starting point to prepare nanoarchitectures ofaramids.

Condensation copolymers and chain-growth polymershave also been obtained. The reaction of polymer P1 withpoly(ethylene glycol) (PEG) monomethyl ether and NaHyieldedablockcopolymerofpolyamideandPEG,P7 [41,42](Scheme 4A). A similar reaction of PEG with polymer P1Scheme 4.


gave rise todiscussed tmers of ar[44].

Followinprotectingcopolymer(Scheme 4Busing a dromethane

4.2. Constit

Unequalinto two tIn asymmenot chemicinduced asare equallyof one funcfunctional g

Wewillasymmetryon the diaciunits becomconstitution

The practrol in onconstitutionAlthough thto constitupolyamidesdeeply affefore, thermcould be coity could beto prepare iordered coconstitutionhave also dstructures icedure inpolymers o

The polysymmetricstructures,tail (HH/Tmers (Scheinuence oferties of pothe theoretpolyamides

as the probability of two adjacent nonsymmetric units ina chain pointing in the same direction, which is used toquantify the overall structural regularity of the polymers.

When XabX is reacted with YccY, the shortest struc-lemen, wh

tinguisen by

[acca]

e [accbour p

iaminence donstituone-stic monion kineraturonometer

een 0.2esearcids prompasymm

ihalobsymmotes se matead, hecentlytion,midesymmeme 6,H/TTan s v254 Cwhich

etaticapreparmer,ol as aconduondenslowlyrdere

the raarisonned wopy, anstrated HScheme 5.

a triblock copolymer [43]. Recent work hashe preparation of well-dened diblock copoly-omatic polyamide and aromatic polyethers

g a similar approach and using an amino-group (Boc, tert-butoxycarbonyl), a block

of polyamide and poly(THF) has been described). A triblock copolymer was also synthesizedifunctional poly(THF) initiated by triuo-sulfonic anhydride [45].

utional isomerism

reactivity of monomers can be classiedypes (asymmetry and induced asymmetry).try, functional groups on the monomer areally equivalent and react at different rates. Inymmetry, functional groups on the monomerreactive until one of them reacts. The reactiontional group alters the reactivity of the secondroup.

considerhere the isomerismassociatedwith theof monomers. The introduction of substituentsds or diaminemonomers, such thatmonomerice symmetrically nonequivalent, results in theal isomerism of the synthesized polymers.tical and theoretical aspects of sequence con-e-step condensation polymerization due to

isomerism were summarized by Ueda [46].e structureproperty relationships attributedtional isomerism are not well known for, onecouldconjecture thatmolecularordermayct the cohesive energy and crystallinity; there-al and mechanical properties and solubilityntrolled, at least partially, if structural regular-selected [4749]. Of course, it is also possible

n several synthetic steps polymers with highlynstitution, and some of the papers related toal isomerism in polyamides mentioned aboveescribed the preparation of perfectly orderedn a time-consuming multi-step synthetic pro-order to compare the characteristics of thebtained by the two methods.condensation of a nonsymmetric (XabX) with a(YccY)monomercangenerate two limitorderedhead to tail (HT) and head to head/tail toT), and an innite set of disordered poly-

ture ebccbindisis giv

s =(

wherIn

1,3-dsequthe cin ametrreacttempthe mparambetwthe raramand cfrom4,6-da nonpromof thto-he

Reterizapolyaon as(Scheof Hwith237from

Lialiphwasmonoalcohwaspolycwasthe oandcompobtaitroscdemoorderme 5). Pino et al. originally examined theconstitutional isomerismon the physical prop-

lyamides [50]. They systematically investigatedical aspects of the structural regularity of the, describing a probability parameter s, dened

the randomthe inuenproperties,

Moreove[52] werets in the polymer are acca, accb, bcca andere the two structures, accb and bcca arehable. The probability s of an accbplacement

[accb]+ [accb] + [bccb])] includes [accb] and [bcca].ast work, we studied the polymerization of

e-4-chlorobenzene [48] (Scheme 6, P11). Theistribution can be analyzed and predicted. Thus,tional isomerism in these polyamides preparedage polycondensation reaction with nonsym-omers was controlled, between limits set byetics, through the polycondensation reactione and the mode of addition and feed rates ofers. The constitutional order in terms of the swas determined by 1H and 13C NMR and varied8 and 0.5. On a subsequent paper we extended

h to the constitutional order and properties ofepared from 1,3-diamine-4-halobenzene [49],red the properties with the polyamides derivedetrically dihalogenated MPDs (1,3-diamine-enzene, halogen= F, Cl, Br). The presence ofetric monohalogen-substituted structural unitolubility and inuences the thermal propertiesrials due to the inherent disorder of the head-ad-to-tail and tail-to-tail sequence distribution., Pat et al. [51] analyzed the synthesis, charac-and constitutional isomerism of new aromatic

containing pendant aryloxy groups basedtrically substituted meta-phenylene diaminesP12). All the polymers showed a prevalencesequences at usual polymerization conditions,

alue between 0.35 and 0.37, Tgs in the range of, and good solubility in polar aprotic solventslms could be cast.

al. investigated ordered HH/TTromatic polyamides. Poly(amide-ester) [47]ed by direct polycondensation of a symmetricisophthaloyl chloride and 4-aminophenethylnonsymmetric monomer. The polymerizationcted under the standard low-temperaturesation method, but the isophthaloyl chlorideadded to 4-aminophenethyl alcohol to give

d HH/TT poly(amide-ester). The HH/TTndom poly(amide-ester)s were prepared forpurposes. The microstructure of the polymersas investigated by 1H and 13C NMR spec-nd model reactions were studied in detail toe the feasibility of polymer formation. TheH/TT polymer was semicrystalline, while

poly(amide-ester) was amorphous, showingce of constitution in microstructure, physicaland transformability.r, ordered HH/TT semiaromatic polyamidesprepared by direct polycondensation of


a symmetphenylethyThe polycoof the formordered polroute. The risophthaloyN-methyl-2solubility waddition, anin the ordersame Tg (1steric effectthe chainThe therma10% weightWe believedecompositof the amiN-arylationthe bulkineeffects men

A discuconstitutionindentiedof Ueda [46

4.3. Spheric

The outsPPPT derivecan be desof the intemake theing, and insthe all-parameta-phenypendant subeasier to m

eamie bondation oe modspeciaa lack

chainitingertieseometer matsulatissemb.hericaynthett-freeeight

th [55. Diveof lowyfunctScheme 6.

ric monomer, isophthalic acid with N-lenediamine as a nonsymmetric monomer.ndensation was carried out by slow additioner to the latter. Conversely, HH/TT and HTyamideswere reliably obtained by amulti-stepandom polyamide was synthesized by mixingl chloride and the diamine all at once in-pyrrolidinone. Regarding properties, a higheras observed for the random polyamide. Inunexpected lack of crystallinity was observeded and disordered polymers, all exhibiting the52 C), attributed by the authors to the larges of the pendant phenyl group,which restrictedmovement to form a regular conformation.l stability can be described in terms of theloss in the inert atmosphere at around 360 C.that the lack of crystallinity and identical

ion temperatures are because of the inhibitiondeamide interchain hydrogen bonds on thehalf of the backbone amide groups, and thatss of the phenyl moiety is related to the sterictioned by the authors.

amidamidalkylby thfore,causeinterexhibproplike gpropencapself-ations

Spent sdefecular wgrowstepstiona polssion on constitutional isomerism regardingal order, theory, and the polyamide structuresover the last decade can be found in the reviews] and Gentile and Suter [53].

al-like aromatic polyamides

tanding mechanical and thermal properties offrom their regular and linear structure, which

cribed as rod-like, and from the effectivenessrchain hydrogen bonds. These characteristicspolymer fairly intractable, resistant to melt-oluble in organic solvents. The modication ofaromatic structure by means or introducinglene moieties in the main, asymmetric, bulkystructures, etc. increase its solubility andmake

elt. The change in properties is dramatic if the

globally symis based ontral core mgrow in one

Howevemuch easiepolymerizamonodispelinear, anddegreeof brof branchinwhich are a

Overviewtions of denwere recenand Kakimreader to tde linkages are inhibited. Thus, the interchains can be completely suppressed by means off the amidic nitrogen or partially suppressedication of the polymer architecture. There-lty polyamide geometries, such as a sphere,of chain entanglement, deeply inhibiting the

interactions, yielding highly soluble polymerslow solution viscosity and poor mechanical[54]. Nevertheless, polymers with spherical-ries have special properties, which make themerials for novel applications related to theiron characteristics, catalysis, chromatography,ly, as well as medical and biological applica-

l-likepolymer shapes canbeobtainedbydiffer-ic strategies. Dendrimers are ideally spherical,and monodisperse polymers of known molec-. They are prepared by convergent or divergent], and their synthesis is comprised of multiplergent growth is based on the stepwise addi-molecular mass building blocks starting fromional molecule (core) that generates radial and

metrical growth,while the convergent growth

the reaction of preformed dendrons onto a cen-olecule [56], from which dendritic structuresdirection from the core molecule.

r, thepreparationofhyperbranchedpolymers isr, using a one-pot reaction following the usualtion strategies. They are neither defect-free norrse, and are characterized by a ratio of dendritic,terminal units than can be described by theanching [57,58], or by themostprobabledegreeg [58], and by the average number of branches,ll empirical metrics.s of the synthesis, properties, and applica-

dritic and hyperbranched aromatic polyamidestly published by Scholl et al. [59] and Jikeioto [54]. To avoid redundancy, we remit thehese works. Jikei et al. focused on prepara-


tion methods of dendrimers by conventional stepwisereactions known as the orthogonal/double-stage conver-gent approach, and dendrimer synthesis using unprotectedbuilding blocks. The authors described the preparations ofhyperbranched polyamides via self-condensation of AB2,and new polymerization systems using AB4, AB8, A2 +B3,A2 +BB2 monomers. The effect of copolymerization of AB2and AB monomers on the properties was also addressed.Scholl et al. revised the synthetic strategies outlined byJikei et al. for dendrimers and hyperbranched aromaticpolyamides, and summarized their applications in thepreparation of metallic [6063] or magnetic nanoparticles[64], which included the modication of the rheologicalproperties of linearpolyamides [65,66] anduse as a supportfor protein immobilization [67].

5. Expanding the applications of the aromaticpolyamides

5.1. Polyamides with specialty properties

5.1.1. Optically active polyamidesAs is well known, many natural products are optically

active, andwe live inwe use areMany highlas proteins,

Consequration of chSome applshould be nric synthesenantiomeruid crystals[19]. The mmerizationpolymerizacally inactiv

Regardinapproach, sand will be

Mallakpour et al. [19,21] synthesized pendant poly-isophthalamides having a lateral l-isoleucine core group.All polymers were prepared from two methods usingaromatic diacids and diisocyanates (Scheme 7): rst, theconventional high-temperature solution method, and sec-ond, using MW. Both methods were employed usingdifferent catalysts (dibutyltin dilaurate: DBTDL, pyridine,triethylamine, or no catalysts). The best results wereobtainedwithDBTL,underMWradiationaswell as conven-tional heatingpolymerization. All polymers showedopticalrotation [], which veried their optical activity. Polymersprepared by different methods showed different opticalrotation, and this fact was attributed to the dependenceof the optical rotation on the overall structure and regular-ity of the resulting polymer chains. Surprisingly, polymersof the same chemical structure polymerized by the samemethodwith different catalysts resulted in different valuesof [], i.e., the []D25 is 28.5 and +28.5 for P14a polymersobtained employing DBTL and triethylamine (TEA) as cata-lysts, respectively. However, the bulkiness of the pendantaliphatic substructure inuences the polymer properties,resulting in fairly soluble materials having a low thermalstability (5% weight lost around 210250 C).

e autally acre, theied athey he in gaic misimi

s havior ms hav

by MW[15,1

ent thitedC (Td5and 2ated ftion [7in this context it is no exaggeration to say thata chiral world. Moreover, most of the drugsderived from natural sources and are chiral.

y important naturally occurring polymers, suchDNA, and polysaccharides, are optically active.ently, the design, characterization, and prepa-iral polymers are of particular interest [68,69].ications of optically active polymers (OAPs)oted: assembling chiral media for asymmet-is, chiral stationary phases for resolution ofs in chromatographic techniques, chiral liq-in ferroelectrics, nonlinear optical devices, etc.ethods of preparing OAPs involve the poly-of optically active monomers and asymmetriction, which produces OAPs starting from opti-e monomers.g aromatic polyamide synthesis, the simplesttarting with chiral monomers, is generally useddiscussed herein.

Thoptictectuclasstion,phasracem

InmideP19)groupandventsefciexhib300

113estimequa

Scheme 7.hors claim that since these polymers aretive and have aminoacids in the polymer archi-y are likely biodegradable, and are therefores environmentally friendly polymers. In addi-ave the potential for use as the chiral stationarys chromatography (GC) for the separation ofxtures.lar work, OAPs, specically polyisophthala-ng a pendant l-alanine (Scheme 8, P15 andethionine (Scheme 8, P16) and phthalimidee been prepared under conventional heating

methods employing ionic liquids as sol-6,27,24]. The MW heating was clearly morean classical thermal heating. The polymersdecomposition temperatures greater thanbetween 270 and 380 C) and Tgs between

08 C. The limiting oxygen index (LOI) wasor P16 using the Van Krevelen and Hoftyzer0] (LOI =17.50.4CR, where CR is the char


yield obtaiclassifyingfashion, OAbutanoylamphthalimidacid and awere descrline, Schemcontaininggiving optiproducts [2122.4, Tg65%. The amaterials toScheme 8,Td10s rangin

The samration of opderived frodiacid chloreaction ofmethods:densationhigh-tempereaction tim(reaction tifor all polyc

They alsfrom trimetion of theis depicted

f the mred heen 0.fully cses. ThScheme 8.

ned by TGA), and was greater than 35, thusthe polymers as self-extinguishing. In a similarPs derived from 5-(2-phthalimidyl-3-methylino)isophthalic acid or (2S)-4-[(4-methyl-2-

ylpentanoylamino)benzoylamino]isophthalic

tion orendebetwwereanalyromatic diamides (Scheme 8, P17 and P18)ibed and characterized [71,24,26,28]. In thise 8, P20, depicts similar polymer structuresa pendant perbromophthalimidyl moiety,

cally active ame retardant polyamides as5]. The []D25 values ranged from 75.8 tos from 197 to 236 C, and the LOIs were overuthors expanded the study of these kinds ofother bulky pendant structures, as depicted in

P21, where the polyamides showed moderateg from 340 to 385 C, and Tgs over 180 C.e research group [72] reported on the prepa-tically active (OA) poly(amide imide)s (PAIs)

m N,N-(4,4-oxydiphthaloyl)-bis-(s)-(+)-valineride. The polymers were prepared by thearomatic diamines with the diacid by three

classical low-temperature solution polycon-(reaction time: 2h at 5 C and 8h at rt),rature polycondensation (reux conditions,e: 1min), and MW polycondensation reaction

me: 6min). Comparable results were obtainedondensation procedures.o synthesized new poly(amide imide)s derivedllitylimido-l-phenylalanine [73]. The prepara-monomer, N-trimellitylimido-l-phenylalanine,in Scheme 9. The direct polycondensation reac-

To concderived frodration of dwas usedof an OA dsize OAPs bvia three potion, polymdiacids halof diacids apolycondenties betweepolymers wmers prepa>300 C, whfacial polyclater probabwas observ

5.1.2. LumiLight-em

nescence mnescence,polyamidestoluminescelectric curonomer imidediacid with different diaminesigh yield PAIs with relatively low inh values21 and 0.45dL/g. All of the above compoundsharacterized by IR spectroscopy and elementale []D25 varied between 1.0 and 3.6.lude this section, we comment on a productm the hydrogenation and subsequent dehy--glucose, 1,4:3,6-dianhydro-d-sorbitol, which

as the starting chemical for the preparationiamine [74]. This has been used to synthe-y the reaction of diacids or diacids dichlorideslymerization methods: interfacial polymeriza-erization in solution under MW irradiation ofides and diamines, and direct polymerizationnd diamines (Scheme 10). The MW-assistedsation lead to polymers with inherent viscosi-n 0.22 and 0.73dL/g, the other methods yieldedith lower molecular weights. The Tgs of poly-red by MW heating ranged between 115 andile the values of polymers prepared by inter-ondensation ranged between 34 and 60 C, thely corresponding to oligomers. The same trend

ed in the Tms.

nescent and electrochromic polyamidesitting phenomena is a characteristic of lumi-aterials. Among the different types of lumi-we consider here light-emitting aromaticthat produce electroluminescence (EL) or pho-

ence (PL) phenomena, upon exposure to anrent or due to absorption of photons causing


Scheme 9.

re-radiationluminescenerature, andreaders area thoroughpolymers.

Additionstanding m

ers sing diing dipolymover,romisit a rexidize[75,76], respectively. The physics underlyingce have been extensively described in the lit-are beyond the scope of this study. Interested

referred to Akcelrud [76] and Kim et al. [75] fortreatment of the characteristics of luminescent

ally, the lm formation properties and out-echanical properties of aramids make these

polymemittemitttionMoretrochexhibare oScheme 10.uitable for the production of organic light-odes (OLEDs), and specically polymer light-odes (PLEDs). Despite this, classical condensa-ers are rarely studied for these applications.some luminescence materials also show elec-m (EC), a phenomenon in which materialsversible change in optical properties when theyd and reduced. Electrochromic materials are


nowbeen exploited in diverse applications such asmirrors,displays, windows, and earth-tone chameleon materials[77].

There is currently much research directed toward thepreparationlight can bdyes, whicherating alllight by thirings are prthe polymerings have aitates the ial. [78,79] doxadiazolepolymers wdiacid dichlperatures.Tds betweethin lms cNMPsolutiobetween 46sive blue PLinvestigateding a smoosurface. Thetions in optadvanced

Liou et amatic polymain chaingroups at thpolyamideswere solublity, with a Twith char y229 and 29bands at 26in the solidimum bandin solution,state. The lamineunittransmittanranging 32diamine wielectrochroing color froto the bluetials from 0groups intorials resultethe colorati

The momers contahigh-efciedation prodparapara tbenzidine adimmer, thtaining ele

substituents on the pendant phenyl ring, thus providingstable radical cations upon oxidation.

The Liu research group [81] prepared and evalu-ated blue-light-emitting and anodically electrochromic

rials o

yltriphmonmer ince quong utum ycoup

mideging corials wnts ane withgs valurforme subenylamis(4-ahenyleily ofituted(Scheers P

alues4 C, wilute sg absoaximaolyamoptic

escedderiv

mmogmtinsible0.98Volyamabilitywish ntentiaing pency (Cast rat64%

ation,lectrog >50

s.gardin(Schemylamint polydiamimidesures rC, andle in Tof blue light-emitting polymers, because bluee converted to green or red using the proper

means a blue PLED alone is capable of gen-colors, while green or red cannot emit blues method. In this regard, the 1,3,4-oxadiazoleomising chemicalmoieties for introduction intor backbone or in the pendant structure. Thesen electron-withdrawing character, which facil-njection and transport of electrons. Bruma etescribed aromatic polyamides with the 1,3,4-rings in the lateral structure (Scheme 11). Theere prepared by the reaction of diamines withorides by solution polymerization at low tem-The polymers were thermally stable, with an 410 and 420 C, showed good solubility, andould be spin-coated on silicon substrates fromn forPLmeasurements, showingPLmaximums0 and 475nm, which corresponded to a inten-. The characteristics of the lm surfaces wereby atomic force microscopy (AFM), show-

th, homogeneous, and practically defect-freeauthor highlighted several potential applica-

oelectronics, microelectronics, or other relatedelds.l. [80] synthesized non-coplanar rigid-rod aro-amides containing biphenylene units in the, and bulky naphthyl or phenyl of pendante 2,2-disubstituted position (Scheme 12). Thewere readily soluble in organic solvents (somee in THF), and showed excellent thermal stabil-d5s between 425 and 530 C in N2 atmosphereields higher than 60%, and high Tgs, between2 C. They exhibited strong UVvis absorption2353nm in NMP solution, and at 318349nmstate (lms), and their PL spectra showed max-s at 440462nm in the purple to blue regionand maximum bands at 435530 in the solidlms made of polyamides without the tripheny-s showedhighoptical transparency fromUV/visce measurements with cut-off wavelengths3345nm. The polyamide derived from theth triphenylamine moieties revealed excellentmic contrast and coloration efciency, chang-mthepale yellowishneutral, to green, and thenoxidized forms during positive scanning poten-.0 to 1.2V. The incorporation of bulky naphthylthe polymer side of the electrochromic mate-d in lighter-colored polymers, thus enhancingon efciency at higher contrasts.st widely studied EC polyamides are poly-ining a triphenylamine moiety, a well-knownncy chromophore. Since the one-electron oxi-uct of triphenylamine is not stable due to theail-to-tail coupling, which yields tetraphenyl-nd the concomitant lost of two protons pere authors primarily prepared monomers con-ctron-rich para triphenylamine moieties as

matemetha commonorescea strquanredoxpolyachanmatesolvestabland T

PelamintriphN,N-b1,4-pa famsubstunitspolymTgs vof 54The dstronPL mThe pwereuorthosevoltaindiurever0.95The pEC styelloat pocolorefcicontrup tocolorThe ecyclinstatu

Re[83]phendirec4,4-polyaperat480

solubf aramids derived from 4,4 -dicarboxy-4 -enylamine monomer, a monomer containing

high-efciency chromophore (Scheme 13). Thes a blue-light emitter (454nm) and has uo-antum yields of 46%. The polymers showedorescence emission in the blue region with

ields up to 64%, and one reversible oxidationle around 1.20V in acetonitrile solutions. TheEC characteristics showed excellent stability,lor from the original pale yellow to blue. Theere readily soluble in conventional polyamided someof themeven in THF, andwere thermallya Td5s up to 507 C, char yields higher than 60%,es ranging from 252 to 309 C.

ing further work on the tripheny-structure, Hsiao et al. [82] reported on aine-containing aromatic diamine monomer,

minophenyl)-N,N-bis(4-tert-butylphenyl)-nediamine, and its polymerization to giveelectroactive polyamides with di-tert-butyl-N,N,N,N-tetraphenyl-1,4-phenylenediamine

me 14A). The polymers were amorphous, and29b, P29e, and P29f were soluble in THF. Thewere 269296 C, and the Td10s was in excessith char yields over 62% at 800 C in nitrogen.olutions of these polyamides in NMP exhibitedrption bands centered at 316342nm, and aaround 362465nm in the violet-blue region.ides derived from aliphatic dicarboxylic acidsally transparent in the visible region andwith a higher quantum yield compared withed from aromatic dicarboxylic acids. The cyclicrams of the polyamide lms cast onto anoxide-coated glass substrate exhibited two

oxidation redox couples at 0.570.60V andversus Ag/AgCl in an acetonitrile solution.ide lms exhibited both electrochemical and, with a color change from a colorless or paleeutral form, to green and blue oxidized formsls applied from 0.0 to 1.2V. These anodicallyolymeric materials showed high colorationE=216 cm2/C for the green coloring) and highios of the optical transmittance change (T%),at 424nm and 59% at 983nm for the greenand 90% at 778nm for the blue coloration.activity of the polymer remained intact after0 times between its neutral and fully oxidized

g the triphenylamine core, Kung et al.e 14B, P30ah) described adamantoxytri-

e-containing polyamide prepared by themerization of the dimine 4-(1-adamantoxy)-notriphenylamine with aromatic diacids. Theshowedmoderate tohighglass-transition tem-anging from 263 to 311 C, Td10s values abovewere fairly soluble; thus, P30e and P30f wereHF. The polyamides exhibited strong UVvis


Scheme 11.

Scheme 12.


absorptionthePL spectThe cyclic vpair of revepotentials (anacetonitrstable EC pand 1.11.2pale yellowdized form.

Liou andtype triphemerization(Scheme 14of 63103a mediumnitrogen atalso showe362nm and493nm inyield of 4.4onto an indited one oxin an acetwere stableless to gree1.10V.

Continucore, a N,N,tive was uswith bulkyphenyleneddifferent cThe polymdiacid mon

ylenedtrongUion anra shoion anrochemrevers0.64,

e-elect,N-terepea

ns. Wh0 to 0Scheme 13.

bands at 313364nm in NMP solutions, andra showedemissionpeaks around432465nm.oltammograms of the polyamides showed onersible redox waves with oxidation half-waveE1/2) in the range of 0.780.81 versus Ag/AgCl inile solution. Inaddition, thepolymersdisplayedroperties by repeated cyclic scans between 0.0V, showing color changes from a colorless orish neutral to a dark blue or bluish green oxi-

Lin [84] also described an electron-rich AB-nylamine-based monomer, and its homopoly-to yield an electrochromic aromatic polyamide

phenhad ssolutspectsolutelectfourE1/2 =singlN,N,NeachcatiofromC). It had weight-average molecular weightg/mol, exhibited good thermal stability withTg value (282 C), a Td10 of 475 C under amosphere, and char yield at 800 C of 64%. Itd maximum ultravioletvisible absorption atexhibited uorescence emission maxima at

NMP solution with a uorescence quantum%. The cyclic voltammogram of a polymer castiumtin oxide-coated glass substrate exhib-idative redox couple at 0.72V versus Ag/AgClonitrile solution, and the EC characteristics

as indicated by a color change from color-n at applied potentials ranging from 0.00 to

ing with the electron-rich triphenylamineN,N-tetraphenyl-p-phenylenediamine deriva-ed by Chang and Liou [77] to prepare aramidslateral groups. The N,N,N,N-tetraphenyl-p-iamine is an anodic EC chemical, and emitsolors depending upon the oxidation state.ers and the preparation procedure of theomer containing the N,N,N,N-tetraphenyl-p-

second, thicharacterispolyamidePappeared apolymer coyellowish toxidation salso measuand 308 C,according tgreater than

Hsiao epolyamidesmonomer hThe opticalby UVvisstrong UVsolution, anaround 421polyamidesimilar to tsolid-stateiamine are depicted in Scheme15. ThepolymerVvis absorptionbands at 351363nm inNMPd at 405419nm in the solid state; their PLwed maximum bands around 450504nm ind 508516nm in lms. As an example of theical and EC properties, polymer P32g showed

ible oxidationredox couples at Eonset = 0.35,0.84, and 0.99V corresponding to successiveron removal from the nitrogen atoms at bothtraphenyl-p-phenylenediamine structures inting unit to yield stable delocalized radicalen the applied potentials increased positively.65, 0.75, and 1.14V, corresponding to the rst,

rd, and fourth electron oxidations, the peaktic absorbance at 359nm for the neutral form32gdecreasedgradually,while fournewbands

t 1030, 999, 831, and 800nm, respectively. Themplementary colors changed fromoriginal paleo green, and then to blue due to the differenttates. The other polymer characteristics werered, with high Tgs values, ranging between 233and they are considered to be thermally stableo the Td5 value above 480 C and a char yield68% under an N2 atmosphere.

t al. [85] also studied the properties ofcontaining the triphenylamine-based

aving a bulky tert-butyl group (Scheme 16).properties of the polyamides were investigatedand PL spectroscopy. The polymers showedvis absorption bands at 314361nm in DMAd their PL spectra exhibited emission peaks430nm, which is in the blue region. Theabsorption spectra of the solid state werehose in solution (a little red-shifted), and thePL spectra were almost identical to those in


dilute DMA. The EC characteristics were also measured,and when increasing the potential from 0 to 1.10V, thecharacteristic absorbance peak at 356nm for polyamide4f decreased gradually, while two new bands appeared at635 and 801nm, because the electron oxidation produceda stable cationic radical. The lm color became green. ThePAs had high Tgs values between 282 and 302 C, and Td10sranged from 458 to 498 C, while char yields were greaterthan 60%. Additionally, polymer 4f was also soluble in THFat ambient conditions.

In similar work, Liou et al. [86] synthesized anddescribed the photophysical and electrochromic char-acterization of wholly aromatic polyamide blue-light-emitting materials, which have a carbazole-derivedtriphenylamine-containing aromatic dicarboxylic acidmonomer, 4,4-dicarboxy-4-N-carbazolyltriphenylamine(Scheme17). The polymerswere amorphous and gave ex-ible, transparent, and tough lms with good mechanicalproperties. They had good thermal stability, as indicatedby high Tgs (269322 C), and Td5s values between 478and 528 C in N2 atmosphere. These polymers exhibitedstrongUVvis absorptionmaxima at 340361nm, PL emis-

sion peaks at approximately 449465nm, and quantumyields up to 46% in NMP solution. The lms exhibitedone reversible oxidative redox couple at potentials of1.111.18V versus Ag/AgCl in an acetonitrile solution,attributed to the oxidation of the main-chain tripheny-lamine unit. The polymer lms were electrochromicallystable, changing color from original yellowish to deepblue.

Therehasbeen furtherworkon triarylamine-containingaromatic polyamides. Green-light-emitting polymersbearing anthrylamine chromophores, 9-[N,N-di(4-carboxyphenyl)amino]anthracene, were studied by Yenand Liou [87] (Scheme 18). The aromatic polyamides wereamorphous and had signicantly high thermal stabilitydue to the high softening temperatures (Ts) (290300 C),a Td5s up to 505 C, and char yields over 60% at 800 C innitrogen. The polymers showgood solubility, andP35d andP35e are even soluble in THF. All PAs exhibited high opticaltransparency as indicated by the UVvis transmittancemeasurement with cut-off wavelengths between 423 and433nm, and exhibited a green emission maximum around478484nm in the solid state. The polyamides exhibited aScheme 14.


high PL quaand had one1.10 and solutions, r

Liou et acardo uorThe introdupolymer bacapability, a366 C; Td5sshowed UVsolution anPL spectrathe purple-in the lms

UVvlengthmideoloratorm tontialse remidesorineuoreshemicgh aScheme 15.

ntum yield in NMP solution (from 55% to 74%),oxidation and reduction couple (Eonset) nearly

1.50V versus Ag/AgCl in acetonitrile and DMFespectively.l. [88] also prepared aromatic polyamides withine moieties in the main chain (Scheme 19).ction of the cardo uorine moiety into the

ckbone enhanced the solubility, lm-formationnd the thermal stability (Tgs between 318 andin N2 between 525 and 540 C). The polymer

vis absorption bands at 286348nm in DMAd 295345 in the solid (lm) state, and their

fromwavepolyaand ctral f(pote

Wpolyaor uThe are cthrouexhibited maximum bands at 452456nm into-green region in DMA solution, and 451520. The lms showed high optical transparency,

binding sitein both thesignaling u

Scheme 16.is transmittance measurements with cut-offs in the range of 296391nm. Moreover, thec exhibited excellent electrochromic contrastion efciency, changing from the colorless neu-green, and then to dark blue upon oxidation

from 0.00 to 1.35V).cently investigated uorescent aromatic

that had bulky dansyl, uorine pendant,moieties in the main chain [89] (Scheme 20).cent signals of the dansyl or uorine moietiesally associated with the main polymer chainsurea group, a well-known supramolecular

. They also uoresce yellowish-green or bluesolution and solid state depending on the

nit, with the former corresponding to the


Scheme 17.

Scheme 18.

Scheme 19.


Scheme 20.

dansyl and the latter to the uorine residue. The PAs hadhigh Tgs values up to 331 C, and low Tds values around300 C, due to the moderate thermal stability of the ureagroup.

Gao et al. [90] took an alternate approach by exploit-ing polyaniline as a promising organic conducting polymer,and prepared and analyzed the properties of polyamideswith well-dened oligoaniline segments in the main chain(Scheme 21). Polyamides with BOC protected oligoanilinesequences were soluble in common organic solvents, suchas dichloromethane, chloroform, and acetone. In additionlms could be cast from the corresponding solutions. Theprotecting groups were removed by dipping the polymerlms into aqueous HCl solutions at ambient temperature,

or by heating at 180 C under an argon atmosphere. Theelectrochemical analysis of polyaniline shows two pairs ofredox peaks. Unlike polyaniline, polymers P40a and P40bshowed three oxidation peaks at approximately 0.4, 0.7,and 0.8V. This behavior is not easily interpreted, and isdiscussed extensively in the original work. The polymersoxidized at 0.20V (yellow lm) showed only one peakat 300nm, and a minimum absorbance in the visible andnear infrared (NIR) spectra. When they were oxidized at0.45V (green lm) or 0.75V (blue lm), strong absorbancewas observed in the visible and NIR regions, and causedthe delocalization of the radical cation (polaron) alongthe doped copolymer backbone structure. While oxidizedat 1.00V (purple lm), the polymers showed intensityScheme 21.


Scheme 22.

Scheme 23.

Scheme 24.


in the free-carrier tail and a blue-shift of the polaronband.

Nechifor [91] examined a monomer diacid havingtwo coumarin moieties in the main chain and in thependant structure, namely 6,6-methylenebis{2-oxo-8-{2-[(2-oxo-2H-chromen-7-yl)oxy]acetoxy}-2H-chromene-3-carboxylic acid} (Scheme 22), which was polymerizedwith various aromatic diamines to give a series of newaromatic polyamides with photosensitive coumarin pen-dent groups (inh of 0.400.87dL/g). The bulkiness ofthe side lateral structure creates amorphous poylamideshaving increased solubility, and is soluble in aprotic polarsolvents as well as less polar solvents like THF. The Tgsvalues were moderate, in the range of 221257 C, andthe decomposition temperature reasonably good in air(Td =370383, Td10s =390410 C). Polymer lms wereprepared via induced crosslinking between polyamidemolecules through a [2+2] photocycloaddition atthe double bond of coumarin moieties and irradiated(>300nm). The emission spectra of polymer solutionsshowed a band with a maximum at 387nm. The uores-cence spectra of the lms showed red shifts of 18nm inthe emission maxima.

5.1.3. Polyamides in membrane technologies5.1.3.1. Reverse osmosis and nanoltration. Reverse osmo-sis (RO) is a water purication technique that reduces thequantity of dissolved solids in solution [92]. The technol-ogy depends mainly on complex polymer semipermeablemembranes having a dense barrier layer where separa-tion occurs. In most cases the membrane is designed toallow only water to pass through this dense layer whilepreventing the passage of solutes (such as salt ions). One ofthe most important applications of RO is the production ofdrinking water from brackish or seawater. The techniqueis also applied to obtain water for industrial processes thatrequirehighquality, puriedwater, such in semiconductor,biochemical, medical, and domestic applications.

Aromatic polyamides have been used for many yearsin RO membranes. Aromatic polyamides usually form theactive layer, and exhibit high salt rejection, water perme-ability, and fouling tolerance [93]. The thin layer is obtainedby interfacial polycondensation of trimesoyl chloride withmeta-phenylene diamine, and polymerization takes placeon a microporous polysulfone membrane. Among otherapplications, these membranes are used in wastewatertreatment, seawater desalination, and dialysis.Scheme 25.

Scheme 26.


Improverine resistaKonagayadiamine compiperazine,terephthalosolubility ities. The acopolyamidperformancNOMEX-typstill a high[95,96].

Mohameasymmetricof a whoeither 4-aScheme 27.

ments in the ux, salt retention, and chlo-nce are currently major topics in this eld.et al. [94] prepared copolyamides from the

onomers 3,3- or 4,4-diaminodiphenylsulfone,and diacid dichlorides such as isophthaloyl oryl. The random copolyamides had excellentn organic solvents and mechanical proper-symmetric membranes prepared from thees not only have better reverse osmosise, but also higher chlorine resistance thane aromatic polyamides, which otherwise is-performance material for this application

d and Al-Dossary [97] prepared at sheetreverse osmosis membranes comprised

lly aromatic polyamidehydrazides, usingmino-3-hydroxybenzhydrazide or 3-amino-

4-hydroxybeither teretures of bovarious ratanalyzed. Ton membravarying theof the castthe thermacoagulatedmembraneexample, twithin the ra higher consalt rejectio

Buch etsured the

Scheme 28.enzhydrazide having equimolar amounts ofphthaloyl or isophthaloyl dichloride, or mix-th, in the solvent DMA. Polymers made usingios of para- to meta-phenylene moieties werehe effects of various processing parametersne transport properties were investigated bytemperature and the solvent evaporation timemembranes, the coagulation temperature oflly treated membranes, the annealing of themembranes, casting solution composition,thickness, and the operating pressure. For

he salt rejection was measured above 80%equired level of permeability. Polymers havingtent of meta-phenylene rings exhibited highern.al. [98] prepared, characterized, and mea-

chlorine stability of aromaticcycloaliphatic


polyamide thin lm composite membranes. The nanol-tration membranes contained the polyamide skin layeron a reinforced polyethersulfone ultraltrationmembrane,and were prepared by in situ interfacial polymerization of1,3-cyclohechloride in hthe performmembranesskin layer pcentrationsexposure otion containthe scanninsion of theskin layer iversion of tnon-hydrogrejection dwater the The amounrine concenindicating tmembrane

The intrin the actthe performm-phenylenmembranespolyamide-lm througisocyanato-a crosslinkiNCO and Cmatic polyaacylamide,isocyanatehydrolyzedbrane perfosalt rejectio

Konagayunder diffecopolyamidodiphenyls(3,5-diamindiaminobenchlorides.by castinggood ROmembranesdiaminodipwith terephRO performindicated b142L/mday

5.1.3.2.the most imaration andenvironmening interestimproved pbranes in

Examples include the separation of carbon dioxide andwater from natural gas, nitrogen and sulfur oxides fromindustrial gas streams and polluted atmospheres, theenrichment of synthesis gas, the recovery of hydrogen from

onia sorm aitry [1ere areparat

techcationbranets, areomatito be vtivity fnergyer ch

MPI, psponsts arey, bymhydromateroved gthis rily of. Theexhibiy valurer =1en higics. Fu2, H2/uch famid

a non, whics the hed theoe experee vo

this105] sportophenatic pothe

isophtis (4-agas peBarrerolymg posases th, depesix tim

ributedchain sility ae selecxanebis(methylamine) in water with trimesoylexane under different conditions. As expected,ance, i.e., salt rejection and water ux, of thewas strongly dependent on the polyamide

reparation conditions, includingmonomer con-, reaction time, and curing temperature. Uponf the membrane to 1, 3, or 5ppm NaOCl solu-ing 2000ppm NaCl for different time periods,g electron micrographs indicated the conver-smooth granular structure of the polyamidento a rough granular nature, due to the con-he hydrogen bonding amide NH group to theen bonding amide NCl. The membrane saltecreased from the initial 78% to 6365%, andux decreased from 73L/hm2 to 3238 L/hm2.t of decrease was dependent upon the chlo-tration, and occurred within 24h of exposure,hat N-chlorination itself adversely affects theperformance.oduction of other chemical functional groupsive layer of RO membranes can improveance of the membranes over the standardediamine (MPD)trimesoyl chloride (TMC). Thus, the preparation of an RO compositeurea membrane on a polysulfone supportingh interfacial polymerization with MPD and 5-isophthaloyl chloride (Scheme 23), which isng agent with trifunctional groups includingOCl, produced active layers comprised of aro-mide with the functional bonds of urea andfrees amines from the hydrolyzed functionalgroups, and frees carboxylic acids from thefunctional carbonyl chloride groups. Themem-rmance, in terms of ux (up to 40 L/hm2) andn (up to99%)washigher than thatof TMCMPD.a and Tokai [99] studied the synthesisrent polymerization conditions of ternaryes from aromatic diamines (MPD, diamin-ulfone), aromatic diamines with carboxylobenzoic acid) or sulfonic groups (2,4-zenesulfonic acid), and iso- or terephthaloylThe at asymmetric membranes prepared

with some of these materials showedperformance and high chlorine resistance;

prepared via the copolymerization of 3,3-henylsulfone and 3,5-diaminobenzoic acidthaloyl dichloride are on example. Thus, theance of the polyamides was improved, as

y a salt rejection up to 97.3% and ux up to.Gas separation membranes. Gases are amongportant commercial products, and their sep-purication have a high economical and

tal impact. In this regard, there is a grow-in the development of novel polymers with

erformance to be used as permselective mem-the separation of gas and vapor mixtures.

ammgen findus

Thfor sbraneapplimemaspec

Areredselecsive epolymand Pare reefforenergchainyieldimpr

Ina famposesTheyabilit1Baror evplast(O2/Nate mTrogrwith18.3)offerformof thand f

In[104,transbenzaromfrombutyl2,2-bThe102

rier pin rinincreP43aup tois attintermeabin thynthesis, the separation of nitrogen and oxy-r, and several other uses in the petrochemical00].e current environmentally friendly processesion and purication methods by gas mem-nologies that are cost-effective for selectives. Nevertheless, new polymer structures andpreparation procedures, as well as theoreticalstudied to increase membrane performance.c polyamides have been traditionally consid-ery efcient barrier materials due to their highor gas separation. Nevertheless, the high cohe-associated with the high packing density of theains of the traditional aramids, such as PPPTroduces extremely low gas permeabilities, andible of theprocessingdifculties. Thus, researchdirected toward the reduction of this cohesiveeans of lowering the effectiveness of the inter-gen bonds, thus increasing the free volume, toialswith superior solubility (processability) andas permeability.egard, de Abajo et al. [100103] investigatedpolyamides especially designed for these pur-polymer structures are depicted in Scheme 24.ted good permeability to gases (the gas perme-es P, are expressed henceforth in Barrer, where010 [cm3(STP) cm]/[cm2 s cmHg]), comparableher than that of glassy, engineering thermo-rthermore, the selectivity to selected gas pairsCH4, CO2/CH4) was acceptable. Gases perme-aster through these polyamides than through(an amorphous aliphaticaromatic polyamide-regular chemical structure and a CO2/CH4 =h is probably the commercial polyamide thatighest permeability to gases. The authors per-retical calculations conrming the consistencyrimental results with conformational freedomlume.regard, Carrera-Figueiras and Aguilar-Vegatudied the synthesis, the thermal and gas

properties, permeability, and selectivity ofone and hexauoroisopropylidene containinglyisophthalamides and copolyamides derived

copolymerization of isophthalic and 5-tert-halic acids with 4,4-diaminebenzophenone orminophenyl) hexauoropropane (Scheme 25).rmeability coefcients for P43a are arounds for O2, which classies this polymer as a bar-er. The inclusion of a bulky tert-butyl groupition ve of the isophthalic residue drasticallye permeability (P44a is up to 15 times that of

nding on the gas being considered, and P44b ises more permeable than P43b). This behaviorto an increase in the fractional free volumeandpacing, and a concomitant rise in the gas per-nd diffusion coefcients. However, a decreasetivity of gas pairs is generally observed. The


experimental results for the gas permeability coefcientsand permselectivity for the copolyamides was describedby a semi-logarithmicmixing rule for the homopolyamidespermeability coefcients as a function of their volume frac-tion. The phomopolyaArrhenius-t

The percontainingwere investGas permeameasured athat P37c hcients whattributedmer compaall gases teperature foconsideredwith high Tthan for poP37a).

The pretion charac2,3-dihydromain chain(Scheme 27polyamidesistics, likegas separaplanar diacproperties.1,1,1,3,3,3-gas permeaseparationdirect polyues, whichP45h).

5.1.3.3. Ionbranes aretechnologiccal synthesand electricsively studimechanical

The ionmoieties inblock aromexaminedtheoreticalMechanicalfrom thesethan 20), asulfonatedthe methancould be coshowing phwith respec(swelling)poly(ether

posed by Jo et al. [109] as proton exchange membranes infuel cells. One of the polyamides had a comparable protonconductivity (105mS/cm) to that of Naon 117 at 80 C.

Polyaonmenostgue the scules,et, orthis inest ise devenitionysts, onder te of tl matnationonmencules.has b

ophilicnionser ph

eliminous enmidesphaseful catesults

30%midetion. T51.0202 tods valrthermmidesas pencatio

y metldernxperimg as croupsown-6benz

r or acition m-phasetivity.of Pb(cetona setover,, in bos, and, Cr(IIIextra

c intermeability temperature dependence for themides and copolyamides was described by anype equation.meation properties of aromatic polyamidescardo groups, 4,4-(9-uorenylidene) moieties,igated by Lpez-Nava et al. [106] (Scheme 26).bility coefcients of the three polyamidesweret different temperatures. The results indicateas the largest permeability and diffusion coef-ile P37b has the lowest. These results areto a larger fractional free volume in the for-red to the later. Permeability coefcients forsted show Arrhenius-type behavior with tem-r these aromatic polyamides. The polymers areto be thermally stable (Tds greater than 460 C)gs values (from 284 to 319 C, which is lowerlymer P37c and the higher than polyamide

paration, characterization, and gas separa-teristics of aromatic polyamides containing-1,1,3-trimethyl-1H-indene moieties in thewere described by Ding and Bikson [107]

). The dense membranes prepared with theseshow interesting gas separation character-

high gas permeability coefcients and hightion factors. The nonsymmetric and non-id residue results in desirable gas transportHowever, as expected, polyamides containinghexauoro-2,2-diphenylpropaneexhibit higherbility coefcients and only modestly lower gasfactors. The polymers were prepared by thecondensation method and had high Tgs val-ranged from 251 (P45d) to >400 C (P45g,

exchange membranes. Ion exchange mem-applied in different scientic elds and

al process, including mass separation, chemi-is, energy conversion, and storage in fuel cellal batteries. However, PAs have not been exten-ed for these applications, despite their excellentand thermal properties.exchange capacity based on the sulfonatedthe backbone of homo- and both random andatic copolyaramides (Scheme 28) have beenby Taeger et al. [108]. The materials have aion exchange capacity of up to 3.14mequiv./g.ly stable dense membranes were preparedPAs, and depending on the block length (higherphase separation between sulfonated and non-domains was observed. The water uptake andol crossover of the polyaramide membranes

ntrolled by adjusting the block length.Materialsase separation exhibited enhanced propertiest to methanol permeability and water uptakein comparison to Naon. Similar sulfonatedamide)s structures have been recently pro-

5.1.4.envir

Hdenmolea targwhenits guin threcogcatal

Umancusefuelimienvirmole

Ithydrfor apolymtion/aquepolyaSolidharming rUp topolyato caof 0.3fromlow T

Fupolyaarmssomeheavby Cation eactinsubg18-crthreewatetranssolidselectionand afromMore100%serieCs(II)tivelyspecimides with selective receptors andtal applicationsest or supramolecular chemistry was coined topecic and relatively feeble interaction of twoone acting as a host, or receptor, and the other asguest. The term recognition is specically usedtermolecular interaction between the host andhighly specic, and the host can be employedlopment of technological devices based on itsproperties and capabilities, such as sensors,

r permselective membranes.his premise, and considering the high perfor-he PAs, these polymers could be extremelyerials as tools for the extraction, purication,, or detection of analytes, and particularly fortally damaging cations, anions, and neutral

een pointed out that the urea group impartsity to polymers and is an efcient host unit, which facilitates the preparation of solidases to be used as extractants for the extrac-ation of environmentally toxic cations fromvironments. We [110] synthesized aromaticcontaining urea in themain chain (Scheme29).s of thepolyamides exposed to environmentallyion water solutions gave moderate but promis-in the extraction/elimination of PbII and HgII.of PbII could be extracted from water to thesolid phase with a 1:1 ratio of urea moietieshe polyamides were semicrystalline, with inh8dL/g, exhibited moderate Tgs values ranging272 C, Tms values above 281 C, and relatively

ues around 305 C.ore, metal ions interact selectively withbearing crown ether and oxyethylene dipodaldant structures. The specic interactions with

ns in alkaline, earth alkaline, transition metal,al, and lanthanide cation series was studied

et al. [111] for solidliquid selective extrac-ents. The polyamides had pendant structures

ation host moieties (Scheme 30), with hostbenzo-12-crown-4, benzo-15-crown-5, benzo-, and the three dipodal counterparts of theo-crown units. The solid-phase extraction ofetonitrile solutions of alkaline, earth alkaline,etal, heavy metal, and lanthanide ions usingpolyamides was performed with a degree of

Higher selectivity was observable in the extrac-II) from a set of heavy metal ions in wateritrile solutions, and for the extraction of Cr(III)of transition metals in acetonitrile solutions.the extraction percentage of Pb(II) was nearlyth aqueous and organic media. In each cationdepending on the cation solvent K(I), Ca(II),), Hg(II), and particularly Pb(II) were all selec-cted by solid-phase polyamides. Likewise, theeractions with some cations in alkaline, earth


Scheme 29.

alkaline, transition metal, and heavy metal cations withthe benzo-18-crown-6 polyamide model compound leadto selective extraction in liquidliquid experiments [112].K(I), Ba(II),each of theof the densemembraneous techniqin the solidthrough the

Copolyahost unitsimprove coapplied tocations fromof a crown(Scheme 31tion of twoa lateral urewithMPD. Tunitwas vathe ion andI, II, and III.

related to the composition of the copolymer, and thus tothe cation-to-anion host unit ratio. For the cation extrac-tion from aqueous media with polyamide solid phases, the

er stntageII and Ce seleinnomer fbindindeveloobservylenednt solu

Polyartiesamidsrmancrials aandll a rrior mCr(III), and Hg(II) were selectively extracted forvarious cations. Furthermore, the interactioncomposite model polyamide-cellulose acetatewith Pb(II), which was analyzed using vari-ues, helped elucidate the role of the polyamideliquid extraction of Pb(II) and its transportmembrane.

mides containing cation- and anion-selectivein the pendant structure were synthesized topolymer performance [113]. They were alsothe extraction of environmentally pollutingaqueous media. The cation host unit consists

ether subunit, with urea as the anion receptor). The preparation involves the copolymeriza-isophthalic acid derivatives one containinga group and the other a crown ether moiety hemolar ratio of the crown-ether-to-urea sub-

ried from1/1 to 1/2 and1/3, in order to optimizecounterion ratio of metals with the valencesThe extraction effectiveness and selectivity is

polymperceof Pb

Thgroupmonourea-colorwasphensolve

5.1.5.prope

Arperfomatemalis stisupeScheme 30.ructure design leads to the extraction of highs of HgII (almost 100%) andmoderate extractionrIII.ctive interaction characteristics of the ureat restricted to anions. Thus, a colorimetric diacidor aromatic diamine sensing that contains ag site has been synthesized [114]. Therefore, apment from colorless to blue, brown, or yellowed upon the addition of meta, para, or ortho-iamine, respectively, to polar aprotic organictions of the monomers.

mides with outstanding mechanical

are commonly transformed into high-e bers and fabrics to be used as transformednd composite materials with superior ther-mechanical resistances. Nevertheless, thereesearch interest in obtaining materials withechanical properties to be transformed into


high-strengetc.

Chen eterties of rbers based]bisoxazolwith terephpolycondenbisoxazoleviscosity ofwith PPDcopolyamidand copolyrial. The outvalues abovyield of 67benzobisoxa lyotropiccompared wditions, theimproved btensile mo3.84.1%.

Recentlymatic polyithebulkypegen atomsrigid polyamsubstitutedlureidophenwith inh ba lm-formproperties.138MPa (Pexhibiting latmosphereof lateral linthe polyme

polymroup.heuremersalongatic poly aromhemicathermmide142 Colymermost seir ouli weas 170ry scarials wetweeScheme 31.

th bers, nanocomposite coatings, enamels,

al. [115] studied the synthesis and prop-igid rod homopolyamide and copolyamidesd on 2,6-bis(p-aminophenyl)benzo[1,2-d;5,4-e (Scheme 32). The reaction of this diaminethaloyl chloride via low temperature solutionsation yielded polyamide-containing benzo-units in the main chain, and an inherent1.98dL/g. The copolymerization of this diamineand terephthaloyl chloride yielded a set ofes. The rigid rod-like structure of the polymermer create a predominantly crystalline mate-standing thermal stability, as indicated by Td10se 570 C in oxidizing atmosphere and a char

% at 700 C, increased as the molar fraction ofazole increased. Fibers of P57 were spun fromliquid crystal solution in 100% H2SO4. Whenith PPPT bers prepared under the same con-

cialtythis gtain tmonotion,aromwholthe ctheirpolyaTg offor pTheis thmoduhighoratomatetion btensile strengths of the copolyamide bersy 2033% with tensile strengths of 1.81GPa,duli of 76GPa, and elongations at break of

, we [116] reported on the preparation aro-sophthalamides with different urea groups inndant structures (Scheme33). Oneof thenitro-

of the urea is chemically anchored to the mainide chain, while the other nitrogen atoms isby phenyl, nitrophenyl, naphthyl, or pheny-yl groups. The polyamides were amorphous,etween 0.18 and 1.93dL/g, and demonstrateing capability with outstanding mechanicalThus, they exhibited a tensile strength up to58a) and moduli up to 6.3GPa (P58c), whileow thermal resistance in nitrogen and oxygens (Tds 225275 C) due to the thermal breakagekages. Theurea group imparts hydrophilicity tors, and facilitates the future preparation of spe-

groups.Mohame

azo(co)polyupon heatiture. The hlow-tempeaminosalicychloride orcombinatiopolymer strunits was vphous polyinsoluble, tvents in orranged fromwhich increThe polymeranging froin the hydrers through the easy chemical modication ofContinuing with the research on PAs that con-agroup,we [117] reportedonABcondensationcontaining an amine and a carboxylic acid func-with their polymerization to give main chainly(amideurea)s (Scheme34).When comparingatic polyamides with the poly(amide urea)s,

l resistance in the later polymers increases, andal resistance and solubility is diminished. Thewith all-meta phenylene moieties (P60a) had a, whereas a higher value of 300 Cwas observedP60d, which had all-para phenylene moieties.triking result of the new poly(amide urea)ststanding mechanical resistance: the Youngsre as high as 5.5GPa, and tensile strengths asMPa for unoriented lms prepared at the lab-le by casting. The mechanical behavior of theas attributed to the strong interchain interac-n the amide/urea, amide/amide, and urea/uread et al. [118] described wholly aromaticamide-hydrazides that undergo cyclizationng to yield a main chain oxadiazole substruc-omo and the copolymers were prepared by arature solution polycondensation reaction of p-lic acid hydrazide and either 4,4-azodibenzoyl3,3-azodibenzoyl chloride, or their appropriatens, in DMA at 10 C (Scheme 35A depicts theuctures). Thequantity ofpara-/meta-phenylenearied between 50/50 and 100/0, giving amor-mers as the product. The polymers were fairlyhe salts had to be added to polar aprotic sol-der to be solved, and their intrinsic v

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