Giant thermophoresis of poly(N-isopropylacrylamide) microgel particles

Research output: Contribution to journalArticle

Authors

  • Simon Wongsuwarn
  • Roberto Cerbino
  • Andrew M. Howe
  • Alberto Vailati
  • Roberto Piazza
  • Pietro Cicuta

Colleges, School and Institutes

External organisations

  • University of Cambridge
  • Politecnico di Milano
  • Università degli Studi di Milano and oINFN-Milan

Abstract

Thermophoresis is the rectification of Brownian motion induced by the presence of a thermal gradient ∇T, yielding a net drift of colloidal particles along or against the direction of ∇T. The effect is known to depend on the specific interactions between solute and solvent, and quantitative theoretical models are lacking except in a few simple experimental cases. Both the order of magnitude and the temperature dependence of the thermophoretic mobility DT are known to be very similar for a wide class of aqueous colloidal systems, ranging from latex colloids to polymers, surfactant micelles, proteins, and DNA. Here we show that thermoresponsive microgel particles made of poly(N-isopropylacrylamide) (PNIPAM) do not share, in the temperature range around the -point, these common features. Instead, DT displays an unusually strong temperature dependence, maintaining a linear growth across the collapse transition. This behaviour is not shared by linear PNIPAM chains, for which existing data show DT falling at the transition, with similar values between the expanded coil and collapsed globule states away from the transition point. A possible connection of the observed giant temperature dependence of DT to microgel hydration is suggested.

Details

Original languageEnglish
Pages (from-to)5857-5863
Number of pages7
JournalSoft Matter
Volume8
Issue number21
Publication statusPublished - 7 Jun 2012