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Association and relaxation of supra-macromolecular polymers

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Author(s)

  • Stephen C. Boothroyd
  • David M. Hoyle
  • Thomas C.B. McLeish
  • Etienne Munch
  • Regis Schach
  • Andrew J. Smith
  • Richard L. Thompson

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Publication details

JournalSoft Matter
DateAccepted/In press - 13 Jun 2019
DatePublished (current) - 14 Jun 2019
Issue number26
Volume15
Number of pages12
Pages (from-to)5296-5307
Original languageEnglish

Abstract

This paper describes the structures created by assembling functionalised entangled polymers and the effect these have on the rheology of the material. A polybutadiene (PBd) linear polymer precursor of sufficient molecular weight to be entangled is used. This is end functionalised with the self-associating group 2-ureido-4pyrimidinone (UPy). Interestingly, despite the relatively high molecular weight of the precursor diluting the UPy concentration, the effect on the material's properties is significant. To characterise the assembled microstructure we present linear rheology, extensional non-linear rheology and small angle X-ray scattering (SAXS). The linear rheology shows that the functionalised PBd assembles into large macro-structures where the terminal relaxation time is up to seven orders of magnitude larger than the precursor. The non-linear rheology shows strain-hardening over a broad range of strain-rates. We then show by both SAXS and modelling of the extensional data that there must exist clusters of UPy associations and hence assembled polymers with branched architecture. By modelling the supra-molecular structure as an effective linear polymer, we show that this would be insufficient in predicting the strain-hardening behaviour at lower extension-rates. Therefore, in this flow regime the strain-hardening is likely to be caused by branching. This is backed up by SAXS measurements which show that UPy clusters larger than pair-pair groups exist.

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© The Royal Society of Chemistry 2019. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

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