Dynamic properties of temperature-sensitive poly(N-isopropylacrylamide) gel cross-linked through siloxane linkage

A gel is a water-insoluble polymeric material though it can absorb a lot of water in its network structure. The poly(N-isopropylacrylamide) (PNIPA) gel exhibits a change in volume in response to external temperature changes and this property is useful in many fields. In this manuscript, a novel PNIPA gel was synthesized by using ethylene triethoxy silane (ETEOS) as the cross-linking agent under acidic conditions. This siloxane incorporated PNIPA gel achieves a dramatically rapid response rate when the external temperature is changed. We suggest that the improvement of the response rate could be due to the macroporous structure of the produced polymer network during the polymerization/cross-linking process. This macroporous structure can provide interconnected water release channels and prevent the formation of a dense, thick skin layer at the shrinking course. On the other hand, water can also diffuse into the polymer network through these water channels during the reswelling process.