Phase behavior and shrinking kinetics of thermo-reversible poly(N-isopropylacrylamide-2-hydroxyethyl methacrylate)

Christine Leon, Francisco Solis, Brent Vernon

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


We study the thermodynamic properties of solutions of the physically gelling poly(N-isopropylacrylamide-2-hydroxyethyl methacrylate) [poly(NIPPAm-HEMA)]. We construct its phase diagram and characterize its kinetics of phase separation. This material belongs to a class of thermosensitive, "smart" polymers, that exhibit complex phase behavior. The copolymer studied is liquid at low temperatures and undergoes phase separation near 28 °C, with negligible dependence on concentration. Above the transition temperature we observe coexistence between a polymer-dilute solution and a gel. We show that, upon quick heating, liquid solutions form a homogeneous gel that phase separates (shrinks) from a dilute polymer solution. We find that the evolution of the gel volume fraction is well described by a double exponential decay, indicating the presence of two shrinking regimes in a close parallel to the behavior of chemically cross-linked gels. The first stage is characterized by quick water ejection. In the second stage, slower shrinking is observed associated with internal reorganization of the polymers that allows the creation of gel-forming contacts.

Original languageEnglish (US)
Title of host publicationActive Polymers
PublisherMaterials Research Society
Number of pages6
ISBN (Print)9781605111636
StatePublished - 2009
Event2009 MRS Spring Meeting - San Francisco, CA, United States
Duration: Apr 13 2009Apr 17 2009

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Other2009 MRS Spring Meeting
Country/TerritoryUnited States
CitySan Francisco, CA

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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