Phase behaviour of blend systems containing nitrile copolymers examined by solid-state nuclear magnetic resonance and differential scanning calorimetry

Abstract

Solid-state cross-polarization magic angle spinning (CP-MAS) nuclear magnetic resonance (n.m.r.) and differential scanning calorimetry (d.s.c.) methods have been applied to examine the phase behaviour of binary blends of acrylonitrile/methyl acrylate/butadiene terpolymer (B210) with poly(ethylene- co-maleic anhydride) (PEMA) and poly(oxycarbonyloxy-1,4-phenyleneisopropylylidene-1,4-phenylene) (PC). Spinlattice relaxation times of the protons in the rotating frame for blends and pure components have been measured by monitoring the CP-MAS generated carbon signal intensities as a function of variable proton spin-lock time. Since single component n.m.r. relaxation behaviour was observed over the entire range of compositions, phase homogeneity was demonstrated for the B210/PEMA system. These monophase blends exhibit single-component rotating frame spin-lattice relaxation times, intermediate in value as compared to the pure components. The d.s.c. examinations also showed that B210/PEMA blends have a single composition-dependent glass transition temperature ( T g). By contrast, the solid state CP-MAS n.m.r. study of B210/PC blends revealed that they display multicomponent relaxation behaviour indicating the presence of a mixed phase along with pure phases of each individual polymer. Additionally, based on the d.s.c. measurements, the T g behaviour of B210/PC blends appears to have a three-component character consistent with a multiphase system.