Epoxy resin/polyurethane hybrid networks synthesized by frontal polymerization

We report the first synthesis of the epoxy resin/polyurethane (EP/PU) hybrid networks via frontal polymerization (FP). In a typical run, the appropriate amounts of reactants (poly(propylene oxide glycol), epoxy resin diglycidyl ether of bisphenol A, 2,4-toluene diisocyanate, and 1,4-butanediol with stannous caprylate (as the catalyst)) were mixed together at initial temperature in the presence of toluene (as the solvent). FP was thermally ignited at one end of the tubular reactor, and the resultant hot fronts propagated throughout the reaction vessel. Once initiated, no further energy was required for polymerization to occur. The dependence of the front velocity and front temperature on the catalyst concentration was thoroughly investigated. The samples were characterized with a Fourier transform infrared spectrometer, thermogravimetric analysis, and a scanning electron microscope. EP/PU hybrid networks synthesized by FP have the same properties as those synthesized by batch polymerization, but the FP method requires significantly less time and lower energy input.