Influence of polyelectrolyte on the thermosensitive property of PNIPAAm-based copolymer hydrogels.

A new family of poly(NIPAAm-co-2-acrylamido-2-methyl-1-propanesulfonic acid) [P(NIPAAm-co-AMPSA)] hydrogels was synthesized by incorporating negative charged AMPSA to the backbone of the PNIPAAm-based hydrogel. The effect of polyelectrolyte (i.e., PAMPSA) on the thermosensitive property of PNIPAAm hydrogels was investigated. It was found that P(NIPAAm-co-AMPSA) hydrogels exhibited unique honey-comb-like 3D porous structure having rigid cell wall as well as enhanced mechanical property. The incorporation of AMPSA into PNIPAAm backbones also led to a significant increase in swelling capability at room temperature when comparing to pure PNIPAAm hydrogels. In addition, the shrinking rate upon heating was significantly improved if the AMPSA content in P(NIPAAm-co-AMPSA) hydrogels was less than 10 wt%.