Studies on graft copolymerization of chitosan with synthetic monomers

Studies on graft copolymerization of chitosan with synthetic monomers

K.V.Harish Prashanth,R.N.Tharanathan *

Department of Biochemistry and Nutrition,Central Food Technological Research Institute,Mysore 570013,India

Received 5February 2003;revised 27June 2003;accepted 30June 2003

Abstract

Graft copolymerization of acrylonitrile and methylmethacrylate onto chitosan using potassium persulfate as an initiator was studied.Evidence for graft-copolymerization was obtained by infrared spectroscopy and CP-MAS 13C-NMR data.The appearance of nitrile (–C x N)at 2244cm 21for chitosan-graft-polyacrylonitrile (C-g -PAN)and carbonyl (–C y O)at 1730cm 21for chitosan-graft-polymethylmethacry-late (C-g -PMMA)confirmed graft-copolymerization.CP-MAS 13C-NMR showed the appearance of a signal at 33ppm assigned to the N–CH group.With varying monomer concentration (40–180mM),the percentage degree of substitution varied from 2to 50.Maximum grafting efficiency was obtained with 120mM acrylonitrile and 0.74mM potassium persulfate at 658C for 2h under nitrogen atmosphere for 1%chitosan solution and for C-g -PMMA 140mM methylmethacrylate at 758C gave maximum substitution.X-ray diffraction showed changes in crystallinity pattern.Slightly different mechanisms in side chain substitution for these two copolymers were envisaged.DSC thermogram showed a decomposition peak for C-g -PAN at around 2558C and a melting peak for C-g -PMMA at around 4008C.C-g -PMMA could be thermopressed into films.Residual monomers were not found by HPLC in graft copolymers stored even for longer periods.q 2003Elsevier Ltd.All rights reserved.

Keywords:Chitosan;Polyacrylonitrile;Polymethymethacrylate;Copolymer;Grafting

1.Introduction

Chitin is one of the most abundant biopolymers found in

the shells of crustacea,e.g.crab and shrimp,and cuticles of

insects and also in the cell walls of some fungi and

microorganisms.Chitin consists of N -acetyl-D -glucosamine

repeating units,linked by b -(1!4)bonds.Due to its

inherent intractability,it is often converted to chitosan,2-

amino-2-deoxy-(1!4)-b -D -glucan by hot alkali treatment.

Chemical modification of chitosan is an important topic for

the production of bifunctional materials.Work on graft

copolymer synthesis based on chitin and chitosan and their

application has been reported.Chitosan-g -poly(glycidyl-

methacrylate)copolymer was used for immobilization of

urease (Chellapandian &Krishanan,1998)and other

modifications such as the grafting of methylmethacrylate

onto chitin initiated by tributylborane (Kojima,Yoshikuni,

&Suzuki,1979),poly(3-hydroxyalkonate)-chitosan

conjugates (Yalpani,Marchessault,Morin,&Monosteries,

1991),chitosan modified poly(glycidylmethacrylate–buty-

lacrylate)and chitosan grafted bovine pericardial

tissue-anticalcification properties have been studied (Shanthi &Panduranga Rao,2001).However,modification of chitosan via grafting of vinyl monomers is one of the most effective methods to incorporate desirable properties into chitosan without sacrificing its biodegradable nature.In the present work,the results of a study on grafting of acrylonitrile (AN)and methylmethacrylate (MMA)onto chitosan in terms of different monomer concentrations and using potassium persulfate as a free radical initiator,under innert conditions are described.Further,the effect of grafting on the thermal behaviour and structural aspects of chitosan have been examined.Attempts were made to prepare chitosan membranes out of graft copolymers and also check for any residual monomers using HPLC.2.Experimental 2.1.Preparation of graft copolymers of chitosan Chitosan,as a solution in dilute acetic acid was graft copolymerized under homogeneous conditions by the method of Chellapandian and Krishanan (1998)with the following modifications.0144-8617/03/$-see front matter q 2003Elsevier Ltd.All rights reserved.

Studies on graft copolymerization of chitosan with synthetic monomers

Studies on graft copolymerization of chitosan with synthetic monomers

doi:10.1016/S0144-8617(03)00191-7Carbohydrate Polymers 54(2003)343–http://m.sodocs.net/doc/6093366c910ef12d2af9e7a1.html /locate/carbpol

*Corresponding author.Tel.:þ91-821-514876;fax:þ91-821-517233.

E-mail address:tharanathan@yahoo.co.uk (R.N.Tharanathan).

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