Influence of Molecular Weight on Physical and Mechanical Properties of Linear Symmetric S-(S/B)-S Triblock Copolymers

✍ Scribed by Mahendra Thunga; Ulrike Staudinger; Martin Ganß; Roland Weidisch; Konrad Knoll

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 879 KB
• Volume: 210
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200800440

✦ Synopsis

Abstract

Symmetric linear S‐(S/B)‐S triblock copolymers with 80 wt.‐% of PS having a block composition of 20‐60‐20 and a S/B ratio of 70:30 in the middle block are studied with varying molecular weights ($\overline M _{\rm w}$). Increase in the $\overline M _{\rm w}$ leads to a change in the morphology from disordered to ordered microphase separated structure, as characterised by TEM and SAXS. Two distinct glass transitions for PS‐ and PB‐rich phases are observed from DMA measurements, which are due to phase separation at high $\overline M _{\rm w}$. Rheological studies (master curves) reveal an extended rubbery plateau and a delay in the terminal response with an increase in $\overline M _{\rm w}$, whereas a terminal flow behaviour is observed for materials having a disordered nature at low $\overline M _{\rm w}$. A brittle‐to‐tough transition is observed from tensile tests with the increase in $\overline M _{\rm w}$.

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