MICRODOMAIN CONTRACTION IN MICROPHASE-SEPARATED MULTIBLOCK COPOLYMERS

Linear multiblock copolymers, like their diblock analogs, undergo micr ophase separation and order into periodic morphologies when the blocks are sufficiently incompatible. To explore the conformations of such m aterials, four symmetric poly(styrene-b-isoprene), copolymers with 2n (1 less-than-or-equal-to n less-than-or-equal-to 4) perfectly alternat ing blocks of nearly equal mass have been synthesized. Small-angle x-r ay scattering reveals that the microdomain periodicity decreases with n along the lamellar normal, thereby confirming theoretical prediction s and providing direct evidence for bridging among the 2(n - 1) middle blocks.