CONFORMATION AND DYNAMICS OF POLYMER-CHAINS IN CONDENSED SYSTEMS

A Stockmayer's type-A chain such as cis-polyisoprene (PI) having dipol e components parallel to the chain contour exhibits slow dielectric re sponse, reflecting fluctuation of its end-to-end vector (dielectric no rmal modes). This article reviews our own work on dielectric spectrosc opy for studying dynamics and conformational properties of probe PI ch ains in binary blends with PI or polybutadiene (PB) that does nor exhi bit normal modes. Through such studies we were able to see the crossov er of the probe-chain dynamics from Rouse behaviour in low-molecular-w eight (lmw) matrices to pure reptation behaviour in high-molecular-wei ghr (hmw) matrices. We were also able to confirm experimentally Flory' s earlier prediction on excluded volumes in dilute blends of hmw probe chains in lmw matrices, for which a proof has never been given before .