Cationic Hybrid Copolymerization of Vinyl Ether and Seven-membered Thionolactone
Designing novel copolymerization methods for preparing new copolymers is of significance to synthesize high-value polymer materials.Vinyl and heterocyclic compounds are the most important types of monomers in polymer chemistry,but the controlled copolymerization of the two is a great challenge due to the distinct polymerization mechanisms and reactive centers,which limits the development and application of new copolymer materials.Based on the thionolactone monomers which are studied widely,the cationic ring-opening polymerization of a seven-membered biphenyl-fused thionolactone(DOT)via using common cationic catalyst BF3·Et2O was studied.The structure of this newly synthesized polythioester was confirmed using 1H nuclear magnetic resonance(1H-NMR)and 13C-NMR.Differential scanning calorimeter method(DSC)and thermogravimetric analysis(TGA)indicated that the polythioester exhibits good thermal stability and a high Tg(98 ℃).Subsequently,cationic hybrid copolymerization of DOT and vinyl ether was explored.According to the effects of three types of cationic catalysts on the copolymerization of DOT and isobutyl vinyl ether(IBVE)without a chain transfer reagent(CTA),trifluoromethanesulfonic acid(CF3SO3H)was selected for further investigation.Subsequently,with the use of a scalable and green cationic CTA and the catalyst CF3SO3H,the controlled cationic hybrid copolymerization of DOT and IBVE was developed,producing a new poly(vinyl ether)-block-poly(thioester)copolymer(Mn=7.6-8.0 kg/mol,PDI＜1.40).The block structure of the polymer was further confirmed by diffusion ordered spectroscopy(DOSY)NMR.This study provides design ideas for the development of new methods of hybrid copolymerization and the preparation of new copolymer materials.
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