some properties of poly(carbonates) and poly(thiocarbonates) from diphenols with methyl groups in...

Polymer International 46 (1998) 93È98

Some Properties of Poly(carbonates) andPoly(thiocarbonates) from Diphenols

with Methyl Groups in the 3-Position inthe Phenyl Rings

M. F. Rey-Stolle,1 F. Ferna� ndez-Mart•�n,2 L. H. Tagle3 & I. Herna� ndez-Fuentes*,4

1 Dpto C.C. Ba� sicas, Fac. C.C. Experimentales y Te� cnicas, Universidad San Pablo-CEU, 28660 Boadilla (Madrid), Spain2 Instituto del Fr•� o (CSIC), 28040 Madrid, Spain

3 Facultad de Qu•�mica, PontiÐcia Universidad Cato� lica de Chile, Santiago, Chile4 Dpto Qu•�mica F•� sica I, Fac. C.C. Qu•�micas, Universidad Complutense, 28040 Madrid, Spain

(Received 26 June 1997 ; accepted 12 August 1997)

Abstract : Glass transition temperatures and the corresponding activation ener-gies of poly(carbonates) and poly(thiocarbonates) with di†erent side-chain sub-stituents obtained from diphenols with methyl groups in the 3-position in thephenyl rings have been determined by di†erential scanning calorimetry at severalscanning speeds. Partial speciÐc volume and speciÐc refractive index incrementshave also been obtained by densimetry and refractometry measurements inbenzene at 25¡C. The e†ect of the di†erent substituents on these properties hasbeen analysed. 1998 SCI.(

Polym. Int. 46, 93È98 (1998)

Key words : poly(carbonates) ; poly(thiocarbonates) ; glass transition ; speciÐcvolume; refractive index

INTRODUCTION

Poly(carbonates) and poly(thiocarbonates) derived frombisphenol A present very interesting characteristics thatopen a wide perspective of practical applications. Thesepolymers can be synthesized1 with di†erent side-groupsby phase-transfer catalysis. For this reason, most of theproperties have been analyzed2h8 as a function of theside-chain structure. The e†ect on these properties ofthe substitution of an oxygen atom of the carbonatechain by a sulphur in thiocarbonate has also been dis-cussed.2,3,5,8 In this paper, a new family ofpoly(carbonates) and poly(thiocarbonates) obtainedfrom diphenols with methyl groups in the phenyl ringshave been studied. Scheme 1 shows the general struc-ture of these polymers, where R and R@ represent the

* To whom all correspondence should be addressed.Contract/grant sponsor : DGICYT.Contract/grant number : PB92-0188.

side-groups and M is O in poly(carbonates) and M is Sin poly(thiocarbonates). The poly(carbonates) selectedfor this work have : (R \(R\ wCH3 , R@\ wCH3),

R@\ wPh)wCH3 , R@\wCH2CH3), (R\ wCH3 ,and

that are designated PMCM, PEtCM, PPhCM andPChCM, respectively ; the correspondingpoly(thiocarbonates) are called by analogy PMTCM,PEtTCM, PPhTCM, PChTCM. These hereafter are

Scheme 1. General structure of poly(carbonates) andpoly(thiocarbonates) derived from bisphenol A.

931998 SCI. Polymer International 0959È8103/98/$17.50 Printed in Great Britain(

94 M. F. Rey-Stolle et al.

called Family II. As can be seen, the methyl groups inthe phenyl rings of the main chain introduce importantsteric hindrance. Therefore, it seemed interesting tostudy also the corresponding polymers without methylsubstitution in the aromatic rings, this series of com-pounds being Family I. Some properties of certain poly-mers of Family I are available in the literature ;2,3,9 thusonly the remaining cases will be experimentally treatedin the present study.

The aim of this work was to analyse the e†ect of thedi†erent substituents on some physical properties of thecompounds, such as glass transition temperatures andactivation energies of the glass transition process,partial speciÐc volumes and speciÐc refractive indexincrements. Comparisons between the behaviour of thedi†erent chemical series are performed in order to dif-ferentiate the inÑuence of the presence or absence ofmethyl substitution in the phenyl rings in the mainchain, together with the e†ect of the nature of theside-groups on both poly(carbonates) andpoly(thiocarbonates).

EXPERIMENTAL SECTION

Materials

Samples of poly(carbonates) belonging to Family I :poly(carbonate) of bisphenol A (PMC), poly(carbonate)of 2,2@-bis(4-hydroxyphenyl)butane (PEtC), 1,1@-bis(4-hydroxyphenyl)cyclohexane (PChC) and the corre-sponding poly(thiocarbonate) of the last diphenol(PChTC) studied in this work have been synthe-sized previously with phosgene and thiophosgene,respectively, by phase-transfer catalysis.10 Thesame procedure has been employed to obtainsamples of poly(carbonates) belonging to Family II,2,2@bis(4-hydroxy-3-methylphenyl)propane (PMCM),2,2@-bis(4-hydroxy-3-methylphenyl) butane (PEtCM),

1,1@-bis(4-hydroxy-3-methylphenyl)-1-phenylethane (PPhCM), 1,1@-bis(4-hydroxy-3-methylphenyl)cyclohexane(PChCM) and their respective poly(thiocarbonates) :PMTCM, PEtTCM, PPhTCM and PChTCM. Theinitial samples were fractionated using the procedurealready described elsewhere for other poly(thio-carbonates).11 Number-average molecular weights ofthe selected fractions were determined by size exclusionchromatography (SEC) except for the sample of PEtCwhich was obtained by vapour pressure osmometryin chloroform, using benzyl as calibrating substanceand conÐrming the calibration with standard samples ofpoly(styrene). These results are summarized in Table 1.Benzene Carlo Erba RPE quality dried over Merck 4 Ómolecular sieves was used as solvent in densimetry andrefractometry measurements.

Differential scanning calorimetry (DSC)

Glass transition temperatures were measured with aPerkin-Elmer DSC-2C calorimeter, connected to a dataacquisition station TADS 3700, which was previouslycalibrated by the usual methods. Dry nitrogen(30 cm3min~1) was used as a purge gas. Samples (ofabout 10 mg) in aluminum pans were scanned between300 and 500 K at several heating rates b of 2É5, 5, 10, 15and 20 K min~1. Measurements were carried out on asecond run after heating the sample up to 500 K andcooling down to 300 K, both at the rate of 20 K min~1.

Densimetry

An Anton Paar DMA 55 digital densimeter was used,with distilled water and air as calibrating substances.The temperature in the measuring cell was regulatedwith a precision of ^0É01¡C. Polymer solutions inbenzene were prepared by weight for densimetry and

TABLE 1. Number-average molecular weights of theM1n

poly(carbonates) and poly(thiocarbonates) studied

Poly(carbonates) M1n

Poly(thiocarbonates) M1n

(g molÉ1) (g molÉ1)

Family I Family I

PMC 38·0a – –

PEtC 2·0b – –

PChC 26·0a PChTC 13·7a

Family II Family II

PMCM 51·0a PMTCM 22·0a

PEtCM 56·0a PEtTCM 19·0a

PPhCM 31·0a PPhTCM 31·0a

PChCM 36·0a PChTCM 24·0a

a By size-exclusion chromatography.

b By vapour pressure osmometry.

POLYMER INTERNATIONAL VOL. 46, NO. 2, 1998

11

10

9

2.20 2.25 2.38 2.43 2.48 2.56 2.62 2.68 2.86 2.92

ln (

/)

Tg

2b

1/ (K )Tg-1

Properties of diphenol-derived poly(carbonates) and poly(thiocarbonates) 95

TABLE 2. Middle and onset glass transition temperatures andTg(m )0

and activation energies, and of the poly(carbonates)Tg(o)0 E

i (m ) Ei (o) ,

and poly(thiocarbonates) studied

Polymer Tg(m)0 T

g(o)0 Ei(m) E

g(o)(K) (K) (kcal molÉ1) (kcal molÉ1)

Family I

Poly(carbonate)

PMC 418a — — —

PEtC 407a — — —

PPhC 449a — — —

PChC 448a — — —

Poly(thiocarbonate)

PMTC 411b — — —

PEtTC 375b — — —

PPhTC 454b — — —

PChTC 428b — — —

Family II

Poly(carbonate)

PMCM 379·9 384·0 128·02 130·38

PEtCM 370·4 373·6 113·1 114·30

PPhCM 407·7 413·4 174·22 178·14

PChCM 392·3 397·7 130·6 134·64

Poly(thiocarbonate)

PMTCM 359·6 365·3 110·68 111·51

PEtTCM 332·7 343·0 95·61 96·65

PPhTCM 440·9 443·9 244·99 247·9

PChTCM 401·6 407·1 189·12 192·22

a Ref. 9.

b Ref. 2.

versus for middle temperatures for poly(carbonates) (open symbols) and poly(thiocarbonates) (Ðlled symbols)Fig. 1. Ln (T g2/b) 1/Tgbelonging to Family II : PMCM PEtCM PPhCM PChCM PMTCM PEtTCM PPhTCM(L), (|), (K), ()), (…), (>), (=),

PChTCM (+).


0.86

V2

31

*(c

mg

)-

PEtCM

PMCM

PChCM

PPhCM

PEtC

PChC

PMC

0.82

0.84

0.80

0.84

0.80

0.83

0.79

0.79

0.83

0.81

0.77

0.80

0.76

0 2 4 6

W2310´


(Ðlled symbols) as a function of and (openFig. 2. v2* w2 v6 20symbols) for poly(carbonates) : PMC, PEtC, PChC, PMCM,

PEtCM, PPhCM and PChCM.

refractometry measurements. Polymer weight fractionsin the solutions were in the rangew2 1 ] 10~3 ¹w2¹

6 ] 10~3.

Refractometry

The di†erences between the refractive index of the solu-tions and pure solvent *n were measured at j \ 546 nm

in a Brice Phoenix 2000V di†erential refractometer,calibrated with aqueous KCl at 25¡C.

RESULTS

Glass transition temperatures were determined by bothmiddle and onset methods, and the corresponding T g(m)0and calculated by extrapolation of the experimen-T g(o)0tal data to zero heating rate (b \ 0). Table 2 shows theresults obtained by linear least-squares Ðtting (typicalr2\ 0É99). The activation energy related to the glassEitransition process can be obtained by the Kissingerequation, assuming a Ðrst-order kinetic process :

lnAT g2

bB

\ C] EiRTg

(1)

where R is the gas constant and C is a constant thatdepends on the polymer. This equation has alreadybeen applied to poly(carbonates) andpoly(thiocarbonates) with good results.8 Figure 1 showsthe plots of versus for all theln (T g2/b) 1/Tgpoly(carbonates) and poly(thiocarbonates) studied. Thecorresponding activation energies were obtained bylinear least-squares Ðtting, and are summarized in Table2 for all the polymers studied.

Partial speciÐc volume at inÐnite dilution of eachv6 20polymer was obtained from density measurements ofseveral polymer solutions of di†erent concentrationusing two methods of calculation already described.3The Ðrst uses the rigorous relation :

v6 20\ o1~1C1 [ o1~1

A LoLw2

B0D(2)

where o and are the densities of the polymer solutiono1and pure solvent, respectively, and is the lim-(Lo/Lw2)0

TABLE 3. Partial specific volumes (in cm3 g—1) of poly(carbonates) andv620

poly(thiocarbonates) studied in benzene at 25ÄC

Poly(carbonate) (v620)a (v6

20)b Poly(thiocarbonate) (v6

20)a (v6

20)b

Family I Family I

PMC 0·771 0·776 PMTC 0·790d –

PEtC 0·801 0·811 PEtTC 0·790c –

PPhC 0·762c – PPhTC 0·780c –

PChC 0·783 0·786 PChTC 0·776 0·780

Family II Family II

PMCM 0·821 0·822 PMTCM 0·802 0·800

PEtCM 0·835 0·837 PEtTCM 0·819 0·816

PPhCM 0·807 0·808 PPhTCM 0·799 0·809

PChCM 0·812 0·818 PChTCM 0·808 0·814

a From eqn (2).

b From extrapolation of (eqn (3)) tov2* w

2] 0.

c Ref. 3, in benzene solution.

d Ref. 3, in dioxane solution (benzene insoluble).


Properties of diphenol-derived poly(carbonates) and poly(thiocarbonates) 97

iting slope of the solution density versus polymer weightfraction plot. In the range of concentrations coveredw2by the experiments, this variation was linear (typicalr2\ 0É999) and was obtained by linear least-(Lo/Lw2)0squares Ðtting. The second method extrapolates toinÐnite dilution the apparent speciÐc volume of polymer

obtained through the expression :v2*

v2* \ o~1[ o1~1w2

] o1~1 (3)

In the range of concentrations studied, the variation ofwith is practically linear and has been obtainedv2* w2 v6 20

by linear least-squares Ðtting. As an example Fig. 2shows plots of versus where the values of arev2* w2 , v6 20represented by open symbols for the poly(carbonates)studied. Poly(thiocarbonates) showed similar behaviourand they are not shown for the sake of simplicity. Table3 collects values obtained by the two methods.v6 20

The di†erences between the refractive indices of thepolymer solutions and the pure solvent *n for thepoly(carbonates) and poly(thiocarbonates) studied havebeen measured in benzene at 25¡C as a function of thepolymer concentration c. The speciÐc refractive indexincrement at inÐnite dilution (Ln/Lc)0 has been calcu-lated for each polymer by least squares Ðtting (typicalr2\ 0É99) of experimental results, and the valuesobtained are summarized in Table 4.

DISCUSSION

Comparison of the data from Table 2 leads to the con-clusion that the presence of methyl groups in the 3-position in the phenyl rings of the main chaindiminishes (by about 8%) the values in both series ofTgpoly(carbonates) and poly(thiocarbonates). This behav-

iour is just the opposite to that expected and meansthat these methyl groups modify the preferred confor-mation in such a way that the energy necessary forchain fragments to move is reduced.

The substituent e†ect on the present Family II can besummarized as follows :

1. The change of methyl group in PMCM andPMTCM, for an ethyl group giving PEtCM andPEtTCM, diminishes the value of the becauseTgthe methylene unit that is inserted in the side-chain acts as an internal plasticizer in both seriesof polymers.

2. Poly(carbonate) and poly(thiocarbonate) witharomatic side-groups, (PPhCM and PPhTCM)are the polymers with higher values, as wouldTgbe expected from the bulkiness of the substituentwhich imposes steric restrictivity on the rotationof the main chain.

3. When the quaternary carbon (Scheme I) belongsto a cyclohexyl ring, as in PChCM andPChTCM, the values are higher than in theTgcase of polymers with two aliphatic substituentsbecause the rigidity and volume have beenincreased, but lower than in the polymers witharomatic side groups.

Typically, poly(thiocarbonates) have glass transitiontemperatures lower than the analogouspoly(carbonates) ; this has been explained in terms of thedi†erent contribution to the double bond character ofthe COwO and CSwO groups.2 However, when thesubstituents have a high rigidity, such as aromatic orpolar groups, poly(thiocarbonates) exhibit higher Tgvalues than the respective poly(carbonates).2,8 Datafrom Table 2 conÐrm this general behaviour, the Tginversion being observed in the case of polymers with

TABLE 4. Refractive index increments (Én /Éc)0 (in units of

cm3 g—1) of poly(carbonates) and poly(thiocarbonates)

studied in benzene at 25ÄC

Poly(carbonate)ALnLcB0

Poly(thiocarbonate)ALnLcB0

Family I Family I

PMC 0·1276 PMTC 0·1831b

PEtC 0·0951 PEtTC 0·1256a

PPhC 0·1288a PPhTC 0·1372a

PChC 0·1053 PChTC 0·1306

Family II Family II

PMCM 0·0865 PMTCM 0·1204

PEtCM 0·0821 PEtTCM 0·1042

PPhCM 0·1122 PPhTCM 0·1371

PChCM 0·0966 PChTCM 0·1265

a Ref. 3, in benzene solution.

b Ref. 3, in dioxane solution (benzene insoluble).



phenyl and cyclohexyl side groups : PPhCM andPPhTCM, and PChCM and PChTCM, respectively.Therefore, for this Family II of poly(carbonates) andpoly(thiocarbonates), the values are greatly inÑu-Tgenced by the rigidity and volume of the side-groups in away similar to that already reported2,8 for the corre-sponding Family I. All these conclusions can also bereached from considerations of the activation energy ofthe glass transition process, where values parallel thechange in the respective values (Table 2).Tg

In relation to densimetry, results from Table 3 showthat discrepancies between the values of obtained byv6 20the two methods of calculation are very small (less than1É3%). Comparison of data from Table 3 indicates thatthe partial speciÐc volume increases when methylgroups in the 3-position in the phenyl rings of the mainchain are present. This behaviour is because of thevolume of the methyl groups, and also the higher sterichindrance that these substituents introduced, since thisincrement is higher than that predicted by the groupcontribution method. The substituent e†ect in Family IIis the same as that for Family I,3 as follows :

1. A general additive character of has been foundv6 20in the results for poly(carbonates) andpoly(thiocarbonates) with methyl and ethyl side-groups (PMCM, PEtCM, PMTCM andPEtTCM) in accordance with the statisticalmodel for both types of polymer.12,13

2. The change of an aliphatic group by an aromaticgroup causes a contraction in the polymers as hasalso been observed in poly(siloxanes),14poly(methacrylates) and poly(diitaconates).15

3. The volume of the polymer with an ethyl group ishigher than the one in which the quaternarycarbon belongs to a cyclohexyl ring.

is not signiÐcantly a†ected by the substitution of thev6 20oxygen atom in poly(carbonates) by sulphur inpoly(thiocarbonates), because the maximum di†erencewas about 2É5%, which is within experimental error.

Considering the refractrometric data of Table 4, itcan be observed that the inclusion of the methyl groupsin the 3-position in the phenyl ring of the main chainlowers the value of the speciÐc refractive indexincrement in both poly(carbonates) andpoly(thiocarbonates). The substitution e†ect on (Ln/Lc)0is the same for both Families I and II :

1. The speciÐc refractive index decreases as thelength of the aliphatic side group increases.

2. The substitution of an aliphatic group by an aro-matic group causes an increase in (Ln/Lc)0.

3. Polymers with the quaternary carbon belongingto a cyclohexyl ring have a higher speciÐcrefractive index than those with methyl or ethylside-groups, but a lower speciÐc refractive indexthan those with phenyl side-groups.

The values of (Ln/Lc)0 for poly(carbonates) are lowerthan for the poly(thiocarbonates) carrying the sameside-groups, the di†erences being about 20%. This isexpected because poly(thiocarbonate) solutions are col-oured, while poly(carbonate) solutions are colourless.

ACKNOWLEDGEMENTS

This work has been partially supported by theDGICYT, under project PB92-0188.

REFERENCES

1 Tagle, L. H., D•� az, F. R. & Margozzini, C. J., Polym. Bull., 25(1991) 319 and references cited therein.

2 Yazdani-Pedram, M., Soto, E., Tagle, L. H., D•� az, F. R., Gargallo,L. & Radic, D., T hermochim. Acta, 105 (1986) 149.

3 Fabre, M. J., Tagle, L. H., Gargallo, L., Radic, D. & Herna� ndez-Fuentes, I., Eur. Polym. J., 25 (1989) 1315.

4 Saiz, E., Abradelo, C., Mog•� n, J., Tagle, L. H. & Herna� ndez-Fuentes, I., Macromolecules, 24 (1991) 5594.

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6 Fabre, M. J., Herna� ndez-Fuentes, I., Gargallo, L. & Radic, D.,Polymer, 33 (1992) 194.

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8 Rey-Stolle, M. F., Ferna� ndez-Mart•� n, F., Tagle, L. H. &Herna� ndez-Fuentes, I., Eur. Polym. J. 33 (1997) 295.

9 Brandrup, I. & Immergut, E. H. (eds) Polymer Handbook, JohnWiley & Sons, New York, 1989.

10 Tagle, L. H., D•� az, F. R. & Salas, P., J. Macromol. Sci., Chem., A2,(1989) 1321.

11 Gargallo, L., Soto, E., Tagle, L. H. & Radic, D., J. Appl. Polym.Sci., 35 (1988) 1103.

12 Sundararajan, P. R., Macromolecules, 20 (1987) 1534.13 Hutnik, M. & Suter, U. W., Polym. Prepr., 28 (1987) 293.14 Go� mez-Anto� n, M. R., Horta, A. & Herna� ndez-Fuentes, I., Polym.

Commun., 25 (1987) 5.15 Gargallo, L., Radic, D., Hamidi, N., Ca� rdenas, L., Horta, A. &

Herna� ndez-Fuentes, I., J. Appl. Polym. Sci., 36 (1988) 1495.


some properties of poly(carbonates) and poly(thiocarbonates) from diphenols with methyl groups in...

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