MISCIBILITY AND MORPHOLOGY OF AB C-TYPE BLENDS COMPOSED OF BLOCK-COPOLYMER AND HOMOPOLYMER OR RANDOM COPOLYMER .1. POLYISOPRENE-BLOCK-POLY(METHYL METHACRYLATE) MODIFIED POLYSTYRENE BLENDS/

The miscibility and morphology of AB/C-type blends composed of polyiso prene-block-poly(methyl methacrylate) [PI-b-PMMA] and a modified polys tyrene with hydroxyl-containing units [PS(OH)] has been studied by tra nsmission electron microscopy (TEM). In the blends the density of hydr ogen bonding between C and B block is adjustable. The miscibility and morphology of the blends cast from toluene, which is inert to hydrogen bonding, are found to depend on the hydroxyl content in PS(OH). Immis cibility between PMMA blocks and PS(OH) alters to miscibility when the hydroxyl content in PS(OH) reaches 1,6 mol-%. Little effect of the re lative molecular weight of PS(OH) to that of the PMMA block is found, which is different from that for AB/A-type blends. An apparent effect of the casting solvent on the miscibility and morphology is observed. Being a proton-acceptor solvent, tetrahydrofuran (THF) considerably de creases the miscibility, and a homogeneous microphase structure appear s only when the hydroxyl content reaches 10 mol-%. This implies that t he main driving force for the miscibility between PS(OH) and PMMA bloc ks is hydrogen bonding between hydroxyl groups of PS(OH) and carbonyl groups of PMMA.