Novel copolymer networks via the combination of polyaddition and anionic polymerization

A two-step synthetic route to novel copolymer networks, consisting of polym ethacrylate and polyacetal components, was developed by combining the polya ddition and anionic polymerization techniques. The functional polymethacryl ates containing hydroxyl or vinyloxyl side groups were used as crosslinkers . They were anionically synthesized as follows: the copolymer of 2-hydroxye thyl methacrylate (HEMA) and methyl methacrylate (MMA) was prepared by the anionic copolymerization of 2-(trimethylsiloxy)ethyl methacrylate and MMA, followed by hydrolysis. The copolymer poly(HEMA-co-MMA) thus obtained posse ssed a hydroxyl group in each of its HEMA units. Another kind of vinyloxyl- containing (co)polymer was prepared by the anionic homopolymerization of 2- (vinyloxy)ethyl methacrylate (VEMA) or its copolymerization with MMA. The r esulting (co)polymer possessed reactive vinyloxyl side groups. The copolyme r networks were obtained by reacting each of the above-mentioned (co)polyme rs with a polyacetal prepared via the polyaddition between a divinyl ether and a diol. Three divinyl ethers (ethylene glycol divinyl ether, 1,4-butane diol divinyl ether, and 1,6-hexanediol divinyl ether) and three diols (ethy lene glycol, 1,4-butanediol, and 1,6-hexanediol) were employed as monomers in the polyaddition step, and their combinations generated nine kinds of po lyacetals. When a polyaddition reaction was terminated with a divinyl ether monomer, a polyacetal with two vinyloxyl end groups was obtained, which co uld further react with the hydroxyl groups of poly(HEMA-co-MMA) to generate a copolymer network. On the other hand, when a diol was used as terminator in the polyaddition, the resulting polyacetal possessed two hydroxyl end g roups, which could react with the vinyloxyl groups of poly(VEMA) or poly(VE MA-co-MMA), to generate a copolymer network. All the copolymer networks exh ibited degradation in the presence of acids. (C) 2000 John Wiley & Sons, In c.