Mechanics and chemical thermodynamics of phase transition in temperature-sensitive hydrogels

被引:280
作者
Cai, Shengqiang [1 ]
Suo, Zhigang [1 ]
机构
[1] Harvard Univ, Sch Engn & Appl Sci, Kavli Inst Nanobio Sci & Technol, Cambridge, MA 02138 USA
关键词
Elastomer; Phase transition; Temperature-sensitive hydrogel; Large deformation; POLYMER GELS; N-ISOPROPYLACRYLAMIDE; SWELLING BEHAVIOR; CROSS-LINKING; VOLUME; DEFORMATION; EQUILIBRIUM; DIFFUSION; SURFACE; MODEL;
D O I
10.1016/j.jmps.2011.08.008
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
This paper uses the thermodynamic data of aqueous solutions of uncrosslinked poly(N-isopropylacrylamide) (PNIPAM) to study the phase transition of PNIPAM hydrogels. At a low temperature, uncrosslinked PNIPAM can be dissolved in water and form a homogenous liquid solution. When the temperature is increased, the solution separates into two liquid phases with different concentrations of the polymer. Covalently crosslinked PNIPAM, however, does not dissolve in water, but can imbibe water and form a hydrogel. When the temperature is changed, the hydrogel undergoes a phase transition: the amount of water in the hydrogel in equilibrium changes with temperature discontinuously. While the aqueous solution is a liquid and cannot sustain any nonhydrostatic stress in equilibrium, the hydrogel is a solid and can sustain nonhydrostatic stress in equilibrium. The nonhydrostatic stress can markedly affect various aspects of the phase transition in the hydrogel. We adopt the Flory-Rehner model, and show that the interaction parameter as a function of temperature and concentration obtained from the PNIPAM-water solution can be used to analyze diverse phenomena associated with the phase transition of the PNIPAM hydrogel. We analyze free swelling, uniaxially and biaxially constrained swelling of a hydrogel, swelling of a core-shell structure, and coexistent phases in a rod. The analysis is related to available experimental observations. Also outlined is a general theory of coexistent phases undergoing inhomogeneous deformation. (C) 2011 Elsevier Ltd. All rights reserved.
引用
收藏
页码:2259 / 2278
页数:20
相关论文
共 57 条
[1]   ON THE DRIVING TRACTION ACTING ON A SURFACE OF STRAIN DISCONTINUITY IN A CONTINUUM [J].
ABEYARATNE, R ;
KNOWLES, JK .
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 1990, 38 (03) :345-360
[2]   A CONTINUUM MODEL OF A THERMOELASTIC SOLID CAPABLE OF UNDERGOING PHASE-TRANSITIONS [J].
ABEYARATNE, R ;
KNOWLES, JK .
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 1993, 41 (03) :541-571
[3]   ON THE DISSIPATIVE RESPONSE DUE TO DISCONTINUOUS STRAINS IN BARS OF UNSTABLE ELASTIC-MATERIAL [J].
ABEYARATNE, R ;
KNOWLES, JK .
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, 1988, 24 (10) :1021-1044
[4]   Phase transitions in the system poly(N-isopropylacrylamide)/water and swelling behaviour of the corresponding networks [J].
Afroze, F ;
Nies, E ;
Berghmans, H .
JOURNAL OF MOLECULAR STRUCTURE, 2000, 554 (01) :55-68
[5]   A thermodynamic model of physical gels [J].
An, Yonghao ;
Solis, Francisco J. ;
Jiang, Hanqing .
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 2010, 58 (12) :2083-2099
[6]   Inhomogeneous deformation of elastomer gels in equilibrium under saturated and unsaturated conditions [J].
Baek, S. ;
Pence, T. J. .
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 2011, 59 (03) :561-582
[7]   Diffusion of a fluid through an elastic solid undergoing large deformation [J].
Baek, S ;
Srinivasa, AR .
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, 2004, 39 (02) :201-218
[8]   Phase separation of weakly ionized polymer gels during shrinking phase transition [J].
Bai, G ;
Suzuki, A .
JOURNAL OF CHEMICAL PHYSICS, 1999, 111 (22) :10338-10346
[9]   Micromechanical cantilever as an ultrasensitive pH microsensor [J].
Bashir, R ;
Hilt, JZ ;
Elibol, O ;
Gupta, A ;
Peppas, NA .
APPLIED PHYSICS LETTERS, 2002, 81 (16) :3091-3093
[10]   Doubly temperature sensitive core-shell microgels [J].
Berndt, I ;
Richtering, W .
MACROMOLECULES, 2003, 36 (23) :8780-8785