SPIN-LABEL STUDY OF IMMISCIBLE POLYMERS .5. BLENDS OF LABELED POLY(2-ETHYL HEXYL METHACRYLATE) WITH POLY(METHYL METHACRYLATE) AND POLYSTYRENE

The electron spin resonance (e.s.r.) spectra of poly(2-ethyl hexyl methacrylate) (PEHMA) spin-labelled with nitroxide end groups were recorded over a temperature range for both the pure, bulk polymer and for 1 : 1 (w/w) immiscible blends with poly(methyl methacrylate) (PMMA) and polystyrene (PS). Both PMMA and PS have significantly higher glass transition temperatures than PEHMA, with which they are immiscible. Nevertheless, the glassy component of these blends exerts a retarding effect on the motion of a portion of the spin labels on the PEHMA, as evidenced by the presence of a persistent slow-motion component in the e.s.r. spectra of the blends. These experiments complement our earlier work in which the spin label was attached to the chain ends of the glassy component in a binary blend. The results support our previous conclusion that in a blend of two immiscible polymers, chain ends tend to congregate in the interphase where they experience the combined influences of accumulated free volume and the presence of the other polymer.