3 Citations (Scopus)

Abstract

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 publicationMaterials Research Society Symposium Proceedings
Pages71-76
Number of pages6
Volume1190
StatePublished - 2009
Event2009 MRS Spring Meeting - San Francisco, CA, United States
Duration: Apr 14 2009Apr 17 2009

Other

Other2009 MRS Spring Meeting
CountryUnited States
CitySan Francisco, CA
Period4/14/094/17/09

Fingerprint

Phase behavior
Gels
gels
Kinetics
kinetics
polymers
Polymer solutions
Phase separation
Polymers
Liquids
liquids
ejection
Superconducting transition temperature
Phase diagrams
Volume fraction
copolymers
Thermodynamic properties
Copolymers
thermodynamic properties
transition temperature

ASJC Scopus subject areas

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

Cite this

Leon, C., Solis, F., & Vernon, B. (2009). Phase behavior and shrinking kinetics of thermo-reversible poly(N-isopropylacrylamide-2-hydroxyethyl methacrylate). In Materials Research Society Symposium Proceedings (Vol. 1190, pp. 71-76)

Phase behavior and shrinking kinetics of thermo-reversible poly(N-isopropylacrylamide-2-hydroxyethyl methacrylate). / Leon, Christine; Solis, Francisco; Vernon, Brent.

Materials Research Society Symposium Proceedings. Vol. 1190 2009. p. 71-76.

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

Leon, C, Solis, F & Vernon, B 2009, Phase behavior and shrinking kinetics of thermo-reversible poly(N-isopropylacrylamide-2-hydroxyethyl methacrylate). in Materials Research Society Symposium Proceedings. vol. 1190, pp. 71-76, 2009 MRS Spring Meeting, San Francisco, CA, United States, 4/14/09.
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AB - 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.

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