Preparation and separation function of N-isopropylacrylamide copolymer hydrogels

In this paper, N-isopropylacrylamide (NIPA) was synthesized by acrylonitrile and isopropanol. Poly(N-isopropylacrylamide) (PNIPA) was prepared by a chemical method. The dependence of its swelling behavior on temperature was studied. Results showed that PNIPA hydrogel was a temperature-sensitive gel. Its LCST (lower critical solution temperature) was about 32 degrees C, and its swelling ratio (at 20 degrees C) was about 17-18. Sodium acrylate (SA) and sodium methylacrylate (SMA) were copolymerized with NIPA respectively. Equilibrium swelling ratios of the copolymer hydrogels at lower temperature were two to three times that of PNIPA. The LCST of the copolymer hydrogels could be controlled between 32 and 45 degrees C by adjusting the content of SA or SMA. Kinetics of P(NIPA-co-SA) hydrogels, whether swelling or shrinking processes, were in good agreement with apparent second order kinetic equations. Several experiments were designed to separate aqueous bovine serum albumin solution using the hydrogels prepared above. The separation efficiency was about 80%. Copyright (C) 2000 John Wiley & Sons, Ltd.