Microhardness of styrene/butadiene block copolymer systems: Influence of molecular architecture

The influence of molecular architecture on the mechanical properties of styrene/butadiene block copol- ymers was investigated by means of the microhardness technique. It was found that the microhardness of the sty- rene/butadiene block copolymers is dictated by the nature of microphase separated morphology. In contrast to poly- mer blends and random copolymers, in which the micro- hardness generally follows the additivity rule, the behavior of the investigated block copolymers was found to signifi- cantly deviate depending on their molecular architecture. The glass-transition temperature of the polystyrene phase (Tg-PS), which practically remained constant and that of the polybutadiene phase (Tg-PB), which varied with the change in the block copolymer architecture, apparently do not in- fluence the microhardness values of the block copolymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1670 -1677, 2003