Structural ordering of two-component hyperbranched copolymers

Polystyrene/polyisoprene (PS/PI) two-component hyperbranched copolymers com posed of PS star molecule as the first-generation core were prepared by liv ing anionic polymerization technique: PI branches were comb-likely grafted from the peripheral sites of PS star molecule as the first-generation core. The microphase-separated structures of such hyperbranched copolymers were studied by means of transmission electron microscopy and small-angle X-ray scattering. The hyperbranched copolymers composed of asymmetric composition (PS volume fraction phi (PS) = 0.25) formed a lattice of body-centered cub ic structure in benzene near the overlap threshold (C*). Such cubic lattice changed to cylindrical structure in the bulk film. Thus this hyperbranched polymer led to the order-order transition from cubic lattice to cylindrica l structure in the process of film formation. The hyperbranched copolymers composed of symmetric composition (phi (PS) = 0.43) and asymmetric composit ion (phi (PS) = 0.20) showed lamellar and spherical morphologies in the bul k film, respectively. These microphase separation behaviors were very simil ar to those observed in (AB), star copolymers. (C) 2001 Elsevier Science Lt d. All rights reserved.