ORDER-DISORDER TRANSITION AND ORDERING KINETICS IN BINARY DIBLOCK COPOLYMER MIXTURES OF STYRENE AND ISOPRENE

The order-disorder transition (ODT) and the ordering kinetics have bee n studied in two symmetric diblock copolymers of styrene and isoprene and their binary mixtures with theology. The binary mixtures formed a single microdomain (with lamellar morphology) composed of short and lo ng chains as confirmed by small angle x-ray scattering (SAXS). The ord er-disorder transition temperature (T-ODT), obtained from the disconti nuity in the storage modulus G', varies linearly with the number avera ge degree of polymerization. For shallow quenches, the ordering kineti cs proceed via nucleation and growth. The characteristic time of this process scales with (N) over bar(-1/3), where (N) over bar is the Ginz burg parameter, in agreement with the theoretical predictions [G. H. F redrickson and K. Binder, J. Chem. Phys. 91, 7265 (1989)]. Our results indicate that the ordering kinetics of symmetric diblock copolymers n ear the ODT are fluctuation controlled. (C) 1996 American Institute of Physics.