Swelling thermodynamics and phase transitions of polymer gels

Michael S. Dimitriyev, Ya Wen Chang, Paul M. Goldbart, Alberto Fernández-Nieves

Research output: Contribution to journalReview article

3 Scopus citations

Abstract

We present a pedagogical review of the swelling thermodynamics and phase transitions of polymer gels. In particular, we discuss how features of the volume phase transition of the gel’s osmotic equilibrium are analogous to other transitions described by mean-field models of binary mixtures, and the failure of this analogy at the critical point due to shear rigidity. We then consider the phase transition at fixed volume, a relatively unexplored paradigm for polymer gels that results in a phase-separated equilibrium consisting of coexisting solvent-rich and solvent-poor regions of gel. Again, the gel’s shear rigidity is found to have a profound effect on the phase transition, here resulting in macroscopic shape change at constant volume of the sample, exemplified by the tunable buckling of toroidal samples of polymer gel. By drawing analogies with extreme mechanics, where large shape changes are achieved via mechanical instabilities, we formulate the notion of extreme thermodynamics, where large shape changes are achieved via thermodynamic instabilities, i.e.phase transitions.

Original languageEnglish
Pages (from-to)1-43
Number of pages43
JournalNano Futures
Volume3
Issue number4
DOIs
StatePublished - Oct 2019

Keywords

  • Extreme thermodynamics
  • Phase coexistence
  • Phase transitions
  • Polymer gels
  • Swelling and deswelling
  • Thermoresponsive materials
  • Toroidal hydrogels

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