The Effect of Crosslinking Density on the Dynamic Behaviour of Thermo-Responsive Poly(N-Isopropylacrylamide) Hydrogels

Stimuli-responsive hydrogels are of great interest in many biomedical applications, from drug delivery to tissue engineering. In this work, thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogels are prepared by adding different amounts of crosslinking agent (N,N- methylenebisacrylamide, BIS) in a two-step-freezing polymerization method, which is simple and potentially able to reduce fabrication times and costs. The hydrogel swelling behaviour and the temporal evolution of the volume variation in response to temperature changes are investigated. Results demonstrate how the thermo-responsive behaviour of these materials is related to the content of the BIS crosslinking agent, which is helpful to guide the synthesis of dynamic hydrogels with tunable functional properties.