Mechanical properties of weakly segregated block copolymers 2. The influence of phase behaviour on tensile properties of poly(styrene-b-butylmethacrylate) diblock copolymers

摘要

The tensile properties of poly(styrene-b-butylmethacrylate) diblock copolymers (PS-b-PBMA) were investigated depending on volume fraction of polystyrene (with a constant molecular weight of (M) over bar(n) approximate to 100 kg/mol) and overall molecular weight (constant volume fraction of 65-70% PS). Diblock copolymers in the composition range 37-57% PS show lamellar structures and a partial miscibility due to their weakly segregated phases. In contrast, samples with other compositions are disordered. A transition from ductile to brittle properties was observed at a PS-content of 57%. Using different molecular weights, it was possible to correlate the different states of segregation (disordered, weak and intermediate segregation) with tensile properties where a change from brittle to ductile properties can be found with increasing molecular weight due to the transition from disordered to an ordered state. At higher molecular weights the phases are intermediately segregated and a maximum in tensile strength as well as strain-at-break can be observed. (C) 1999 Elsevier Science Ltd. All rights reserved. [References: 29]