Phase morphology and dynamic mechanical properties of model polyblock copolymers prepared from reactive oligomers

Two polyblock copolymer (BCP) series of the type (P/S) sub n (where P is the oligomeric azoinitiator and S is the styrene block) synthesized by sequential (series A) and simultaneous (series B) photo-initiated polymerization were characterized by small-angle X-ray scattering and by dynamic mechanical analysis. The molar mass characteristics of the BCP were little affected by methods of synthesis, whereas their morphologies and mechanical behaviour in the bulk state were widely different. Reasonably sharp SAXS peaks and distinct log E' falls concomitant to the glass-rubber transitions for the microphases of each chain component for samples of series B were regarded as evidence of a well-ordered, three-dimensional lattice of isolated S domains within a continuous P matrix. In contrast, the absence of well-defined SAXS peaks in the same range of scattering vectors combined with nearly two-fold smaller log E' falls at T sub gP for samples of series A suggested the existence of two co-continuous, randomly interpenetrated microphases of S and P blocks with a broad distribution of microheterogeneities by size.