Nonionic hydrogels by copolymerization of vinylene carbonate and oligo(ethylene glycol) vinyl ethers

Bulk polymerization of vinylene carbonate (VCA) with ethylene glycol monovi nyl ether (EMVE), diethylene glycol monovinyl ether (DMVE) and methyl triet hylene glycol vinyl ether (MTVE), respectively, was carried out. Compared w ith DMVE and MTVE, the yield of the VCA copolymer with EMVE was low due to a side reaction of acetalization. The copolymerization of MTVE with VCA has been shown to produce linear copolymers and alternating copolymers have be en found to form at a 1:1 molar monomer ratio. The copolymerization of EMVE and DMVE with VCA, on the other hand, generally yielded crosslinked copoly mers. The reason may be a radical transfer reaction that occurred at methyl ene groups adjacent to hydroxyl groups of pendent oxyethylene moieties, as inferred from studying the swelling behavior of hydrolyzed copolymers in ac idic aqueous solution. The copolymers and their hydrolysis products, especi ally copoly(MTVE/VCA) and copoly(DMVE/VCA), exhibited low glass transition temperatures, which is apparently due to flexible pendent groups on polymer chains. The copolymerization in the presence of oligo(ethylene glycol) div inyl ethers as crosslinking agents followed by hydrolysis with a 5 wt.% NaO H solution gave rise to the formation of three different nonionic hydrogels . The swelling behavior of all the gels was found to be independent of the presence of some electrolyte salts at various concentrations in an aqueous solution. However, the hydrogels based on copoly(EMVE/VCA) and copoly(DMVE/ VCA) were shown to be unstable under acidic conditions, whereas those based on copoly(MTVE/VCA) were found to be only slightly influenced by the pH va lue of an aqueous medium. (C) 2001 Elsevier Science Ltd. All rights reserve d.