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Vitrification and plastic flow in transient elastomer networks

Published version
Peer-reviewed

Repository DOI


Type

Article

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Authors

Pritchard, RH 
Redmann, AL 
Ji, Y 

Abstract

We investigate how the crossover temperature of the elastic-plastic transition, the ‘vitrification point’ Tv, changes under load for isotropic vitrimers and exchangeable liquid crystal elastomers (xLCEs), using the thermoplastic SIS triblock polymer as a reference. In all these cases, the elastic network cross-links are transient: physical micro-phase separation in SIS and covalent transesterification bonds in vitrimers. From the analysis of SIS we define Tv as the point when entropic rubber-elasticity contraction due to heating under load turns into the irreversible plastic extension due to cross-links breaking and reforming. In xLCEs, the response to mechanical stress is heavily influenced by the smectic liquid-crystalline order, which makes the material much stiffer than normal rubbery networks, and also leads to the shape-memory effect across the smectic-isotropic transition point. The vitrification in the isotropic phase of xLCE, and in isotropic vitrimers, was found to be independent of stress, which can be attributed to the thermal activity of the catalyst determining Tv and it not being mechanically coupled to the elastic network. Beyond Tv, with increasing stress the plastic extension rapidly increases with temperature, as cross-link dynamics becomes more apparent.

Description

Keywords

Vitrimers, Rubber elasticity, Transient network, Liquid crystal elastomers

Journal Title

Polymer

Conference Name

Journal ISSN

0032-3861
1873-2291

Volume Title

95

Publisher

Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/J017639/1)
This work was funded by the EPSRC (EP/J017639), the Ernest Oppenheimer Trust in Cambridge, and by China Scholarship Council.