RHEOLOGICAL BEHAVIOR OF BINARY-MIXTURES OF A BLOCK COPOLYMER AND A HOMOPOLYMER

The rheological behavior of binary mixtures of a block copolymer and a homopolymer was studied. For the study, polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymers having molecular weights of 3900S-93300I-3900S and 7400S-990001-7400S, respectively, and a series of homopolymer polystyrenes (PS) having molecular weights of 1000, 1300,1500, 2000, and 3000, respectively, were synthesized via anionic polymerization, and various mixtures were prepared. For each block copolymer/homopolymer system, a phase diagram was constructed using the combined results of dynamic viscoelastic measurements and turbidity measurements. Rheological properties were measured for (a) single-phase mixtures (H), (b) microphase-separated block copolymer (M1) into which added homopolymer PS is solubilized, (c) two-phase mixtures consisting of microphase-separated block copolymer (M1) into which added homopolymer is solubilized and macrophase-separated homopolymer PS (L2), and (d) two-phase mixtures consisting of disordered block copolymer (L1) and macrophase-separated homopolymer PS (L2). The rheological properties measured were interpreted using information on the morphological state of the materials studied.