research article novel synthesis of cellulose-based ...downloads.hindawi.com › journals › tswj...

Research ArticleNovel Synthesis of Cellulose-Based Diblock Copolymer ofPoly(hydroxyethyl methacrylate) by Mechanochemical Reaction

Takeshi Ohura1 Yusaku Tsutaki1 and Masato Sakaguchi2

1 Faculty of Agriculture Meijo University 1-501 Shiogamaguchi Nagoya 468-8502 Japan2 Institute for Environmental Sciences University of Shizuoka 52-1 Yada Shizuoka 422-8526 Japan

Correspondence should be addressed to Takeshi Ohura ohurameijo-uacjp

Received 18 December 2013 Accepted 2 February 2014 Published 4 March 2014

Academic Editors Z Ma E Odermatt and T K Vaidyanathan

Copyright copy 2014 Takeshi Ohura et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The mechanical fracture of polymer produces polymeric free radical chain-ends by which liner block copolymers have beensynthesized A diblock copolymer of microcrystalline cellulose (MCC) and poly 2-hydroxyethyl methacrylate (pHEMA) wasproduced by the mechanochemical polymerization under vacuum and room temperatureThe fraction of pHEMA inMCC-block-pHEMAproduced by themechanochemical polymerization increased up to 21molwith increasing fracture time (sim6 h)Then thetacticities of HEMA sequences in MCC-block-pHEMA varied according to the reaction time In the process of mechanochemicalpolymerization cellulose could play the role of a radical polymerization initiator capable of controlling stereoregularity

1 Introduction

Cellulose is the most abundant biological resource on theearth which has been applied to composite materials textiledrug delivery systems personal care products and so forth[1] Therefore making efficient use of cellulose would showsuperiority compared to other synthetic polymers in terms ofecological and environmental properties The glycosylationof cellulose has been well studied for a long time and allover the world by which energy and food problems arehoped to be solved However cellulose is structured byrobust 120573-14-glycosidic linkages so that the effectively andsafety techniques have not been established On the otherhand chemical modification techniques of cellulose havebeen developed to provide further functions For instancecelluloid (cellulose nitrate) is the earliest modified cellulosewhich had thermoplasticity as additional functionThe recentadvances of cellulose modifications are expanding fromesterification of cellulose (eg cellulose nitrate and celluloseacetate) to graft copolymerization of cellulose [1] Note thatalmost all of those modified cellulose are graft polymer usinghydroxyl group of cellulose

The mechanochemical reaction has been known to beclassical procedure for synthesizing linear block copolymer

[2]The reaction processes are initially triggered by end-chainradicals (called mechanoradicals) produced by mechanicalfracture of polymer and the mechanism is provided inFigure 4

Indeed the mechanochemical reaction was applied tosynthesize block and graft copolymers of cellulose andvinyl monomers resulted in the block copolymers beingproduced by the mechanical fracture [2] Furthermoresuch mechanoradicals provide us information of molecularmotion of chain by using electron spin resonance (ESR) [3ndash6]

Sakaguchi et al have revealed the scission of the 120573-14-glycosidic linkages of bacterial cellulose (BC) fracturedmechanically under vacuum at 77K from the ESR spectra[7 8] In addition diblock copolymer of BC and poly(methylmethacrylate) was produced by the mechanical fractureindicating that mechanoradicals behave like radical polymer-ization initiator The greatest benefit of mechanoradicals willbe a polymerization procedure with ultimate low environ-mental burden However the potentiality of mechanoradicalpolymerization including the adaptivity and versatility hasbeen unsure at present so that further investigations areneeded to reveal the characterization In the current study

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 127506 4 pageshttpdxdoiorg1011552014127506

2 The Scientific World Journal

400100016002200280034004000

(a)

(b)

(c)

(d)

1710 cmminus1

Wavenumber (cmminus1)

C=O

Figure 1 FT-IR spectra of the MCC-block-pHEMA produced bymechanochemical polymerization for (a) 0 h (b) 1 h (c) 3 h and (d)6 h

we synthesize novel diblock copolymer of accessible and low-cost cellulose MCC and biocompatible materials HEMAby mechanical fracture at room temperature and report thefunction of MCC on the polymerization

2 Experimental

21 Synthesis of MCC-Block-pHEMA The diblock copoly-mers of MCC and pHEMA (MCC-block-pHEMA) wereproduced as follows HEMA (50mg Wako Pure ChemicalsOsaka Japan) purified by freeze-pump-thaw method wasintroduced into handmade glass vessel (50mL) containingprevacuum-dried MMC (50mg Aldrich USA) and aluminaball (10 g 2mm in diameter) and the glass vessel was sealedoff from the vacuum line set to shaker (shaking speed300 rpm amplitude 40mm SA-300 Yamato Scientific CoLtd Tokyo Japan) andmilled in vacuumat room temperaturefor predetermined time (sim6 h) After that all products weresequentially washed by Soxhlet extraction with methanol for16 h to remove unreacted HEMA and the resultant residuewas dried in oven at 80∘C for 12 h

22 Acetylation The acetylation of MCC and MCC-block-pHEMA synthesized was performed to be analyzed by 1H-NMR A mixture of acetic acid (057mol) and trifluoroaceticacid anhydride (0436mol) was held at 50∘C for 20minThenMCC or MCC-block-pHEMA was introduced and the solu-tion was acetylated at 50∘C for 12 h The acetylated productwas precipitated with methanol followed by filtration Afterthat the precipitate was washed by methanol again and wasdried in oven at 80∘C for 12 h

OOO

O 13

4 52

ab

c

d

c d

001020304050(ppm)

A

B a b

1 6 4 523

mm

mr

rr

C

6998400

OCOCH3

OCOCH3

OCOCH3H3COCO

66998400

1 6 4 5236998400

c da bbbbbbb

mm

mr

rr

C

nm

ndashOCOCH3

Figure 2 1H-NMR spectra of the acetylated MCC (A) as controland acetylated MCC-block-pHEMA produced by mechanochemi-cal polymerization for (B) 1 h and (C) 6 h

23 Analyses The chemical structures of MCC and MCC-block-pHEMA produced were analyzed by FT-IR and 1H-NMR FT-IR spectra were observed on a FT-IR 8400 (Shi-madzu Kyoto Japan) using solid KBr pellets 1H-NMRspectrawere recorded on a JNM-BEX270NMRspectrometerat 270MHz (JEOL Tokyo Japan) in CDCl

3 TMS was used

as the internal reference The number and weight averagemolecular weights (119872

119899and119872

119908) of samples were estimated

by using GPC system (Waters 600E) with column ShodexGPC K-805L in chloroform at 40∘C and 08mLmin of flowrate A calibration curve was obtained using polystyrenestandards

3 Results and Discussion

It has been widely investigated that mechanical destructionof cellulose results in the scission of the polymer main-chainfollowed by the production of radicals even under roomtemperature [9ndash11] This fact implies that cellulose fracturedmechanically is possible to react as radical initiator Herewe performed the production of novel diblock copolymerof cellulose (MCC) and pHEMA using mechanochemi-cal polymerization Figure 1 shows the FT-IR spectra ofMCC-block-pHEMA obtained by each reaction time of themechanochemical polymerization Peak at 1710 cmminus1 forC=O group of pHEMA was observed in all reactants but notfor samples for 0 h and without alumina ball Sakaguchi andSohma indicated that material with low molecular weights(sim100) has no function in mechanochemical polymerization[12] so that current polymerization will be attributed to thescission of MCC but not to self-polymerization of HEMAIn addition the intensity of peaks obviously increased withan increase of reaction time from 1 h to 6 h (see Figure 2)

The Scientific World Journal 3

Table 1 Characteristics of MCC-block-pHEMA produced by mechanochemical polymerization

Run Time (h) pHEMA (mol) pHEMA DPa Molecular weight Tacticity ()b

119872

119899

(times103) 119872

119908

119872

119899

mm mr rr1 0 mdash mdash 46 15 mdash mdash mdash2 1 7 23 54 14 391 131 4783 3 30 52 30 16 411 171 4184 6 37 69 32 16 145 382 473aDP degree of polymerizationbmm isotactic rm atactic rr syndiotactic

m m

MCC-block-pHEMAHEMACellulose (MCC)

Radical polymerization

HO

HO

OH

OH

OH

OH

OH

OH

OOOHHO

OHO O O

OO

O

OHO

OHOH

OOO ∙

n

+ n

Figure 3 Reaction scheme of MCC-block-pHEMA production initiated by MCC mechanoradical and sequentially reacted with HEMA

Fracture

X X

CH2

CH2

CH2

Mechanoradicals

nminus1

CH CH2minusCH

+

∙CH2 + nCH2=

∙CH2∙CH2

Figure 4

Indeed the molar ratios of pHEMA in MCC-block-pHEMAcalculated by 1H-NMR increased from 7mol for 1 h to37mol for 6 h (Figure 3) and those degrees of polymer-ization (DP) of pHEMA calculated from corresponding119872

119899

values of the copolymer chains also increased from 23 to69 respectively (Table 1) These facts indicate that radicalpolymerization ofHEMAproceeded successfully fromchain-end-type radicals of MCC cleaved by mechanically fractureThe putative reaction scheme is shown in Figure 3 On theother hand 119872

119899and 119872

119908119872119899of the MCC-block-pHEMA

were somewhat consistent regardless of the reaction time(Table 1) It is suggested that polymerization of HEMA andmechanical destruction of solid MCC could also occursimultaneously in the process

As one of function of cellulose posing it has been knownto be chiral recognition that is act as chiral adsorbent[13] So we next investigated the tacticity of pHEMA intheMCC-block-pHEMA produced by the mechanochemicalreaction using 1H-NMR (Figure 3) At earlier stage (1 h) ofthe reaction molar ratios of isotactic (mm) atactic (mr)and syndiotactic (rr) pHEMA were 39 13 and 48molrespectively (Table 1) For 3-hour reaction those character-istics of tacticity were somewhat consistent with copolymerobtained for 1 h At the latter stage (6 h) however molarratio of the isotactic unit decreased to 15mol whereasmolar ratio of the atactic unit increased to 38mol and

constant for syndiotactic fraction (Table 1) These resultssuggest that radical chain-end of cellulose surface bared bymechanochemical reaction has an ability of stereoregularityin the initial stage of radical polymerization therefore theability could decay with progression of polymerization

In this manner the mechanochemical reaction indicatesthe possible presence of ecofriendly simple and func-tional polymerization to future generationsTheMCC-block-pHEMA will be expected to application of the fields of notonly ecologically friendly products (eg dispersant builderetc) but also biocompatible materials Further investigationswill be needed to reveal the potential

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This research was supported by the Japan Society for theProtection of Science (JSPS) Grant-in-Aid for ScientificResearch (23655147)


References

[1] D Roy M Semsarilar J T Guthrie and S Perrier ldquoCellulosemodification by polymer grafting a reviewrdquo Chemical SocietyReviews vol 38 no 7 pp 2046ndash2064 2009

[2] R J Ceresa ldquoThe synthesis of block and graft copolymers ofcellulose and its derivativesrdquo Polymer C vol 2 pp 213ndash219 1961

[3] S Shimada A Suzuki M Sakaguchi and Y Hori ldquoMolecularmotion of chain end peroxy radicals of polyethylene moleculestethered on a fresh surface of poly(tetrafluoroethylene)rdquoMacro-molecules vol 29 no 3 pp 973ndash977 1996

[4] M Sakaguchi K Yamamoto and S Shimada ldquoA thermo-dynamic study on molecular motion of the peroxide endsof isolated single polymer chains tethered to the surface ofpoly(tetrafluoroethylene) in vacuordquoMacromolecules vol 31 no22 pp 7829ndash7834 1998

[5] Y Miwa T Tanase K Yamamoto M Sakaguchi M Sakai andS Shimada ldquoInfluence of chain end and molecular weight onmolecular motion of polystyrene revealed by the ESR selectivespin-label methodrdquo Macromolecules vol 36 no 9 pp 3235ndash3239 2003

[6] M Sakaguchi K Yamamoto Y Miwa S Shimada M Sakaiand T Iwamura ldquoMolecular mobility of peroxy radicals at theends of isolated polystyrene chains tethered on the solid surfaceof poly(tetrafluoroethylene) in a vacuumrdquoMacromolecules vol40 no 5 pp 1708ndash1712 2007

[7] M SakaguchiMMakino TOhura andT Iwata ldquoMechanoan-ions produced by mechanical fracture of bacterial celluloseionic nature of glycosidic linkage and electrostatic chargingrdquoThe Journal of Physical Chemistry A vol 116 no 40 pp 9872ndash9877 2012

[8] M Sakaguchi T Ohura T Iwata and Y Enomoto-RogersldquoNano cellulose particles covered with block copolymer ofcellulose and methyl methacrylate produced by solid mechanochemical polymerizationrdquo Polymer Degradation and Stabilityvol 97 no 3 pp 257ndash263 2012

[9] Y Sasai Y Yamauchi S Kondo and M Kuzuya ldquoNature ofmechanoradical formation of substituted celluloses as studiedby electron spin resonancerdquo Chemical and PharmaceuticalBulletin vol 52 no 3 pp 339ndash344 2004

[10] Y Nakai E Fukuoka S Nakajima and K Yamamoto ldquoEffectsof grinding on physical and chemical properties of crystallinemedicinals with microcrystalline cellulose I Some physicalproperties of crystallinemedicinals in groundmixturesrdquoChem-ical and Pharmaceutical Bulletin vol 25 no 12 pp 3340ndash33461977

[11] D N S Hon andK S V Srinivasan ldquoMechanochemical processin cotton cellulose fiberrdquo Journal of Applied Polymer Science vol28 no 1 pp 1ndash10 1983

[12] M Sakaguchi and J Sohma ldquoESR evidence for main-chainscission produced by mechanical fracture of polymers at lowtemperaturerdquo Journal of Polymer Science vol 13 no 6 pp 1233ndash1245 1975

[13] A Ichida T Shibata I Okamoto Y Yuki H Namikoshi andY Toga ldquoResolution of enantiomers by HPLC on cellulosederivativesrdquo Chromatographia vol 19 no 1 pp 280ndash284 1984

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Advances in

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Smart Materials Research



MetallurgyJournal of


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MaterialsJournal of


Nano

materials


Journal ofNanomaterials


400100016002200280034004000

(a)

(b)

(c)

(d)

1710 cmminus1

Wavenumber (cmminus1)

C=O

Figure 1 FT-IR spectra of the MCC-block-pHEMA produced bymechanochemical polymerization for (a) 0 h (b) 1 h (c) 3 h and (d)6 h

we synthesize novel diblock copolymer of accessible and low-cost cellulose MCC and biocompatible materials HEMAby mechanical fracture at room temperature and report thefunction of MCC on the polymerization

2 Experimental

21 Synthesis of MCC-Block-pHEMA The diblock copoly-mers of MCC and pHEMA (MCC-block-pHEMA) wereproduced as follows HEMA (50mg Wako Pure ChemicalsOsaka Japan) purified by freeze-pump-thaw method wasintroduced into handmade glass vessel (50mL) containingprevacuum-dried MMC (50mg Aldrich USA) and aluminaball (10 g 2mm in diameter) and the glass vessel was sealedoff from the vacuum line set to shaker (shaking speed300 rpm amplitude 40mm SA-300 Yamato Scientific CoLtd Tokyo Japan) andmilled in vacuumat room temperaturefor predetermined time (sim6 h) After that all products weresequentially washed by Soxhlet extraction with methanol for16 h to remove unreacted HEMA and the resultant residuewas dried in oven at 80∘C for 12 h

22 Acetylation The acetylation of MCC and MCC-block-pHEMA synthesized was performed to be analyzed by 1H-NMR A mixture of acetic acid (057mol) and trifluoroaceticacid anhydride (0436mol) was held at 50∘C for 20minThenMCC or MCC-block-pHEMA was introduced and the solu-tion was acetylated at 50∘C for 12 h The acetylated productwas precipitated with methanol followed by filtration Afterthat the precipitate was washed by methanol again and wasdried in oven at 80∘C for 12 h

OOO

O 13

4 52

ab

c

d

c d

001020304050(ppm)

A

B a b

1 6 4 523

mm

mr

rr

C

6998400

OCOCH3

OCOCH3

OCOCH3H3COCO

66998400

1 6 4 5236998400

c da bbbbbbb

mm

mr

rr

C

nm

ndashOCOCH3

Figure 2 1H-NMR spectra of the acetylated MCC (A) as controland acetylated MCC-block-pHEMA produced by mechanochemi-cal polymerization for (B) 1 h and (C) 6 h

23 Analyses The chemical structures of MCC and MCC-block-pHEMA produced were analyzed by FT-IR and 1H-NMR FT-IR spectra were observed on a FT-IR 8400 (Shi-madzu Kyoto Japan) using solid KBr pellets 1H-NMRspectrawere recorded on a JNM-BEX270NMRspectrometerat 270MHz (JEOL Tokyo Japan) in CDCl

3 TMS was used

as the internal reference The number and weight averagemolecular weights (119872

119899and119872

119908) of samples were estimated

by using GPC system (Waters 600E) with column ShodexGPC K-805L in chloroform at 40∘C and 08mLmin of flowrate A calibration curve was obtained using polystyrenestandards

3 Results and Discussion

It has been widely investigated that mechanical destructionof cellulose results in the scission of the polymer main-chainfollowed by the production of radicals even under roomtemperature [9ndash11] This fact implies that cellulose fracturedmechanically is possible to react as radical initiator Herewe performed the production of novel diblock copolymerof cellulose (MCC) and pHEMA using mechanochemi-cal polymerization Figure 1 shows the FT-IR spectra ofMCC-block-pHEMA obtained by each reaction time of themechanochemical polymerization Peak at 1710 cmminus1 forC=O group of pHEMA was observed in all reactants but notfor samples for 0 h and without alumina ball Sakaguchi andSohma indicated that material with low molecular weights(sim100) has no function in mechanochemical polymerization[12] so that current polymerization will be attributed to thescission of MCC but not to self-polymerization of HEMAIn addition the intensity of peaks obviously increased withan increase of reaction time from 1 h to 6 h (see Figure 2)




119872

119899

(times103) 119872

119908

119872

119899


m m



HO

HO

OH

OH

OH

OH

OH

OH

OOOHHO

OHO O O

OO

O

OHO

OHOH

OOO ∙

n

+ n


Fracture

X X

CH2

CH2

CH2

Mechanoradicals

nminus1

CH CH2minusCH

+

∙CH2 + nCH2=

∙CH2∙CH2

Figure 4


119899


119899and 119872








Acknowledgment



References





















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






119872

119899

(times103) 119872

119908

119872

119899


m m



HO

HO

OH

OH

OH

OH

OH

OH

OOOHHO

OHO O O

OO

O

OHO

OHOH

OOO ∙

n

+ n


Fracture

X X

CH2

CH2

CH2

Mechanoradicals

nminus1

CH CH2minusCH

+

∙CH2 + nCH2=

∙CH2∙CH2

Figure 4


119899


119899and 119872








Acknowledgment



References





















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




References





















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article novel synthesis of cellulose-based ...downloads.hindawi.com › journals › tswj...

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