Change in Young’s modulus of poly(N-isopropylacrylamide) gels by volume phase transition

Abstract

Mechanical properties of poly(N-isopropylacrylamide) (PNIPA) gels were examined both in swollen and collapsed state. Stress–strain curve of the gel in the swollen state was linear and the collapsed gel also showed almost linear stress–strain behavior. The initial Young’s modulus (E₀) in the collapsed state was much higher than that in the swollen state. The number of cross-links increased largely by the introduction of the physical cross-links due to collapse of the gels.