INFLUENCE OF DEFECT DENSITY ON THE RHEOLOGY OF ORDERED BLOCK-COPOLYMERS

Quiescently ordered block copolymer materials contain randomly oriente d grains with concomitant defects and grain boundaries. Current theori es suggest that the anomalous rheological properties of block copolyme rs are related to the average grain size, i.e. defect density. We pres ent rheological data from a concentrated solution of a polystyrene-pol yisoprene diblock copolymer in dioctyl phthalate (70 wt % polymer). Th e sample has a cylindrical morphology in the ordered state. The averag e grain size was changed by over an order of magnitude (0.4 to 7.4 mu m) by adjusting thermal history. The viscoelastic moduli of this mater ial in the frequency range 10(-2)-10(2) rad/s were, however, not signi ficantly affected by this change.