Steady flow and dynamic viscosity of branched butadiene–styrene block copolymers

摘要: Steady flow and dynamic viscosities were determined for symmetrical linear starbranched block copolymers of butadiene styrene above their upper (polystyrene) glass transition. Block structures examined B-S-B, (B-S-)3, S-B-S, (S-B-)3 (S-B-)4. At constant molecular weight total content greater polymers terminating in blocks, irrespective branching. Branching decreased the viscosity either polybutadiene-terminated or polystyrene-terminated polymers, compared at equal Mw. However, comparisons lengths showed that length terminal not weight, governs viscoelastic behavior these to a surprisingly good approximation. This unusual result is rationalized terms two-phase domain structure which persists significant degree melt. Below transition polystyrene blocks effects branching masked by differences morphology unrelated