Synthesis of a new hyperbranched-linear-hyperbranched triblock copolymer and its use as a chemical modifier for the cationic photo and thermal curing of epoxy resins

A new hyperbranched-linear-hyperbranched polymer was prepared in a one pot process by reaction of 4,4-bis(4-hydroxyphenyl)valeric acid and poly(ethylene glycol) (HPH). After characterization by 1H and 13C NMR, SEC, DSC, and TGA, this polymer was used, in proportions of 5, 10, and 15 phr, as a chemical modifier in the UV and thermal cationic curing of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexyl carboxylate epoxy resin. The curing process was studied by calorimetry, demonstrating the accelerating effect of the hydroxyl groups present in HPH's structure. The morphology of the resulting thermosets depended on the curing system used, as demonstrated by FE-SEM microscopy, but in both cases phase separation occurred. Thermosets obtained by thermal curing presented lower thermal stability than UV-cured materials. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012