Mobility and the Glass Transition in Mixed Polymer-Diluent Glasses by NMR

Abstract

AbstractPhosphorous and proton line shape studies of a trioctyl phosphate diluent in polycarbonate and in a fifty-fifty blend of polystyrene with polyphenylene oxide have been performed to monitor diluent dynamics. Both the phosphorous and proton line shapes are superficially bimodal with a narrow, mobile component of the line shape appearing at temperatures well below the thermal glass transition temperatures. Plots of the h.ction of mobile material versus temperature show two step increases separated by a plateau region. This behavior is analyzed in terms of a distribution of activation energies which results in a bimodal description. The bimodal activation energy distribution corresponds to a bimodal correlation time distribution. The more mobile material is identified with diluent molecules in contact with other diluent molecules in a lattice description which assumes a single phase system is assumed with a purely random distribution of diluent and polymer on the lattice.