Dynamic Mechanical Properties of Block Copolymer Blends–A Study of the Effects of Terminal Chains in Elastomeric Materials

Three different polystyrene-1,4 polybutadiene (SB) diblock copolymers were blended with a single polybutadiene continuous SBS triblock to form rubbery networks with controlled amounts of terminal chains of known molecular weight. The mechanical properties of these materials were studied in dynamic uniaxial compression from 0.1 to 1000 Hz at various temperatures between –87 and 85°C. At high reduced frequencies in the glassy and polybutadiene transition regions the terminal chains have no perceptible effect on the components of the complex compliance. At intermediate reduced frequencies a temperature dependent entanglement coupling phenomenon appears if the terminal chains are sufficiently long. At low reduced frequencies the terminal chains contribute to entanglement slippage processes which result in an increase in both the storage and loss compliance.