Morphological behavior of A(2)B(2) star block copolymers

A series of A(2)B(2) four-sun, miktoarm stars of polystyrene and polyisopre ne have been synthesized. The morphological behavior of these materials has been characterized using TEM, SAXS, and SANS, and was found to agree in ge neral with the predictions of Milner's theory for miktoarm star morphologic al behavior. One sample was found to exhibit a cylindrical morphology where lamellae were predicted; this behavior is similar to other discrepancies o bserved in previous studies of miktoarm star morphological behavior. A seco nd sample, predicted to form a bicontinuous morphology, was found to exhibi t hexagonally packed cylinders. The tetrafunctional junction point also res ults in an increase in spacing for the lamellar sample in this series over that of an AB diblock, but not as great as the increase previously observed for A(8)B(8) 16-arm star materials. (C) 1999 John Wiley & Sons, Inc.