Reaction of epoxy resin and hyperbranched polyacids

The condensation reaction between two different epoxy resins and a hyperbra nched polyester (MAHP) [poly(allyloxy maleic acid-co-maleic anhydride)] was studied. We compared two kinds of diglycidyl ether bisphenol A type of epo xy resins with different molecular weights, that is, epoxy resin GY240 (M = 365 g/mol) and GT6064 (M = 1540 g/mol) in this reaction. The results showe d a marked difference in their reaction pattern in terms of ability to form crosslinked polymer networks with MAHP. For the former low-molecular-weigh t epoxy resin, no crosslinking could be observed in good solvents such as T HF or dioxane within the set of reaction conditions used in this study. Ins tead, polymers with epoxide functional degrees between 0.34 and 0.5 were fo rmed. By contrast, the latter high-molecular-weight epoxy resin, GT6064, ra pidly produced highly crosslinked materials with MAHP under the same reacti on conditions. The spherical-shape model of hyperbranched polymer was appli ed to explain this difference in reaction behavior. Hence, we have postulat ed that low-molecular-weight epoxy resins such as GY240 are unable to cross link the comparatively much bigger spherically shaped MAHP molecules. Howev er, using high-molecular-weight epoxy resins greatly enhances the probabili ty of crosslinking in this system. Computer simulations verified the spheri cal shape and condensed bond density of MAHP in good solvents, and submicro n particle analysis showed that the average MAHP particle size was 9 nm in THF. Furthermore, the epoxy-functionalized polyesters were characterized by H-1 NMR and FTIR, and the molecular weights and molecular-weight distribut ions were determined by size-exclusion chromatography. (C) 2000 John Wiley & Sons, Inc.