MICROPHASE SEPARATION IN MODEL 3-MIKTOARM STAR COPOLYMER AND TERPOLYMER .2. DYNAMICS

Dielectric spectroscopy has been employed to study the local and globa l dynamics of polyisoprene in the asymmetric star (polystyrene)(polyis oprene)(2) (SI2) and in the 3-miktoarm star terpolymer (polystyrene)(p olyisoprene)(polybutadiene) (SIE). All measurements refer to the order ed phase where PS cylinders are embedded on the I and I/B matrix, resp ectively. Effectively, we are studying the local and global dynamics o f tethered PI chains in two environments: one made by I-chains (SI2) a nd another by the I/B-chains(SIB). At low temperatures, the PI local s egmental dynamics in SI2 and SIE are different, reflecting the modific ation of the local friction by introducing the faster PB chains in the latter. At higher temperatures, however, this effect diminishes due t o the demixing of I and B. To explore the thermodynamic and mobility e ffects on the global dynamics, we have studied, respectively, a ternar y blend composed of PI, PB, and PS and binary blends of SIB and SIE wi th short PB chains. The PI global dynamics in SI2 and SIE resemble the dynamics of PS stars with additional entanglement effects in the latt er.