ESTIMATION OF FREE-VOLUME IN POLYSTYRENE-POLYPHENYLENE ETHER BLEND PROBED BY THE POSITRON-ANNIHILATION LIFETIME TECHNIQUE

Variations of size, content and size distribution of free volumes in l inear polystyrenes (PS) synthesized by radical processes, with the add ition of miscible polyphenylene ether (PPE) in PS, were observed by po sitron annihilation lifetime measurements. The average free volume rad ius of polystyrene was proved to increase from 0.30 nm (PPE: 0%) to 0. 34 nm (PPE: 100%) and the average intensity, relevant to free volume c ontent, decreased with the increase of PPE. The size distributions of free volume of various PS to PPE ratios also reveal that average free volume size increases and that smaller free volumes decrease by the in crease of PPE ratio. The evidence that the size distribution curve of PS and PPE mixture (1:1) is more similar to that of PS suggests that f ree volumes produced in PS are stable with the addition of PPE and tha t more positroniums annihilate in smaller free volumes generated in PS than in bigger ones formed by PPE, since numbers of free volume overw helm those of PPE. (C) 1998 Elsevier Science Ltd. All rights reserved.