Abstract
Polystyrene of different molecular weights and their binary mixtures are
studied in terms of their various mechanical responses to uniaxial compression at different
temperatures. PS of Mw = 25 kg/mol is completely brittle until it is above its glass
transition temperature Tg. In contrast, upon incorporation of a high molecular weight
component, PS mixtures turn from barely ductile a few degrees below its Tg to ductile
over 40° below Tg. In the upper limit, a PS of Mw = 319 kg/mol yields and undergoes
plastic flow, even at T = −70 °C. The observed dependence of mechanical responses on
molecular weight and molecular weight distribution can be adequately rationalized by the
idea that yielding and plastic compression are caused by chain networking.