SYNTHESIS OF GRAFT COPOLYMERS WITH POLYISOBUTYLENE BRANCH CHAINS

The copolymerization of 4-vinylbenzyl chloride（VBC） and vinyl acetate（VAC） was carried out in toluene at 75℃via radical polymerization using 2,2’-azo-bis-（isobutyronitrile）(AIBN) as an initiator.The random copolymers of poly（4-vinylbenzyl chloride-co-vinyl acetate）(P（VBC-co-VAC）) with number average molecular weight（M;） from 2000 to 6900,relatively narrow molecular weight distribution（MWD,M;/M;ca.2.0） and with different copolymer composition of 4-vinylbenzyl chloride（VBC） from 17 mol%to 62 mol%could be obtained.The P（VBC-co-VAC） copolymers with an average number of 7 to 13 initiating sites of benzyl chloride per macromolecule could be used for the cationic polymerization of isobutylene（IB）.The cationic polymerizations of IB were further conducted by using P（VBC-co-VAC） copolymers as macroinitiators in conjunction with TiCl;at -40℃in CH;Cl;.The effects of VBC/TiCl;（molar ratio） on monomer conversion,M;and MWD of the resultant copolymers were investigated under 3 sets of conditions.It is found that P（VBC-co-VAC）-g-PIB copolymers with relatively narrow MWD（M;/M;ca.2.0） and with terminal tert-chlorine functional groups in branched PIB chains could be successfully synthesized when VBC/TiCl;（molar ratio） was set in the range from 0.10 to 1.12.The unimodal GPC curve of the P（VBC-co-VAC）-g-PIB copolymers by RI detector was almost in harmony with the GPC curve by UV detector.The TEM image of the P（VBC-co-VAC）-g-PIB copolymer stained by RuO indicated that the copolymer formed a two-phase morphology with P（VBC-co-VAC）-rich domains of 20-100 nm in size tethered by PIB branch segments.