LINEAR RHEOLOGICAL BEHAVIOR OF POLYISOPRENE-POLYSTYRENE HETERO-STAR AND LINEAR DIBLOCK COPOLYMER MELTS

Block copolymers of polyisoprene and polystyrene have been synthesised in comparable series of linear diblocks and four-arm stars containing two arms of each chemistry. The linear theology of melt samples, whic h had been briefly annealed, revealed relaxation identified with entan glements, mesostructure and with the small domains. Comparison between the linear and star series indicates that the difference in molecular topology hinders the slower relaxations of the microstructure as well as the ordinary viscoelastic relaxations. A mechanism of suppressed d iffusion perpendicular to the interfaces is proposed.