PREPARATION AND MICROPHASE-SEPARATED STRUCTURES OF (AB)(N) STAR-BLOCKCOPOLYMERS COMPOSED OF SYMMETRICAL DIBLOCK ARMS

The (AB)(n) star copolymers (arm number n = 7-77; polyisoprene blocks = ca. 50 vol%) were synthesized by copolymerization of polystyrene (PS )-block-polyisoprene (PI) diblock anions with divinylbenzene (DVB) in benzene. The arm numbers were controlled by changing the initial conce ntration of the diblock anion or the feed ratio of DVB to the diblock anion end. The microphase-separated structures of (AB)(n) star copolym ers were studied by means of transmission electron microscopy (TEM) an d small-angle X-ray scattering (SAXS). It was found that the (AB)(n) s tar copolymers composed of symmetric arms (n < 77) formed lamellar str uctures. The periodic distances of (AB)(n) star copolymers (n < 77) we re the same as those of the corresponding diblock arms. (C) 1998 Elsev ier Science Ltd. All rights reserved.