Morphological behavior of ASB miktoarm star block copolymers

Abstract

A morphological study of three AsB, six-arm miktoarm star block copolymers is presented. The miktoarm stars are comprised of five arms of polyisoprene and one arm of polystyrene joined together at a single junction point. The strong segregation limit theory for the morphological behavior of miktoarm stars predicts that these materials should form cylindrical (two samples) and lamellar (one sample) morphologies, but only lamellar morphologies were observed by TEM and SAXS. These results are similar to previously reported discrepancies between miktoarm star morphological behavior and the predictions of the theory. Combining the data of this study with that of previous morphological studies of miktoarm star materials, we can track the increasing discrepancy between the experimentally observed morphology and theoretical predictions as the molecular asymmetry parameter, e, increases. The AsB materials in this study were also observed to form exceptionally well-ordered morphologies. © 1999 American Chemical Society.