POLY(ARYLENE ETHER SULFONE)S BY POLYETHERIFICATION .5. EFFECTS OF MOLECULAR-STRUCTURE ON TOUGHNESS

Densities, glass transition temperatures and notched impact strengths (NIS) (before and after storing the test samples at 150-degrees-C) have been measured for several series of poly(arylene ether sulfone)s. Consideration of these data together with those presented in Part 4 and by other workers suggests that for polymers with molecular weights (as indicated by solution viscosity) above the entanglement molecular weight, the symmetry of the polymer chains is the most important structural factor deciding NIS. Polymers with the more symmetrical chains provided test samples showing relatively high values for NIS, while the less symmetrical ones, especially those containing phenylene rings linked by ortho- or meta-oriented inter-ring bonds, gave samples for which lower NIS values were obtained. Following recent advances defining the importance of crazing in brittle failure, it is suggested that this effect of symmetry on NIS arises because increasing asymmetry leads to higher values for the chain contour length between entanglements.