Modification of epoxy resins with block copolymers of poly(ethylene oxide) and poly(butylene oxide).

摘要

Block copolymer modified epoxy resins have generated significant interest since itudwas demonstrated that the combination could lead to nanostructured thermosetsudthrough self-assembly.udIn this work, samples of epoxy resin - formed by reaction of bisphenol-A diglycidyludether (BADGE) and diethyltoulenediamine (DETDA) - and containing a range ofudcopolymers composed of poly(ethylene oxide) (E) and poly(butylene oxide) (B),udwere prepared and characterized. Samples contained EB, EBE and BEB copolymersudover a range of concentrations. Copolymers of low molecular weight and low Budcontent were found not to microphase separate. BEB copolymers with highudmolecular weight and high B content were found to macrophase separate prior to, orudduring, cure.udFTIR spectroscopy during cure demonstrated that the reaction kinetics in theseudsystems differ from those previously reported for similar systems.udOver moderate to high copolymer concentration the systems behaved as expected ofuda block copolymer in a solvent selective for one block. As concentration increased,udtransitions from BCC-Hex-Gyr-Lam phases were observed by SAXS.udAt lower concentrations, in some systems, spherical micellar structures were formed,udas demonstrated by TEM. SAXS analysis was performed on those systems producingudsufficiently clear patterns. Some degree of reaction-induced microphase separationud(RI/lPS) was observed in all cases. A linear increase in scattering intensity withudextent of reaction was observed during RI/lPS. In some cases non-equilibriumudstructures were apparently observed, due to vitrification prior to completion of theudRI/lPS process. The increase in the number of micelles as a function of concentrationudwas analyzed and found to deviate from linearity as the system goes from a solutionudof copolymer in epoxy to swollen copolymer gel. The association number of theudmicelles was found to vary as a function of copolymer composition following audsimilar scaling law to that observed, by others, in aqueous solution.udReaction-induced macrophase separation was observed in some BEB systems atudelevated temperature, but not in similar EBE systems. The process was characterisedudby SALS and found to fit to the Cahn-Hilliard linear theory of spinodaluddecomposition. The systems were seen to vitrify before phase separation is complete,udproducing cured products that were phase separated into interpenetrating networksudon the micron scale.udNo significant improvement of mechanical properties of the resin was observed inudthose samples tested.