Super porous organic–inorganic poly(N-isopropylacrylamide)-based hydrogel with a very fast temperature response

Macroporous Poly(N‐isopropylamide‐co‐acrylamide) Hydrogels Prepared by Two‐Step Polymerization for Drug Delivery Applications

“…The systems frozen before gelation were not studied. However, an interesting finding of a recent report [19] showed that the samples frozen before their gelation performed dramatically better than the hydrogels frozen after their gelation. The results exhibited that the moment at which the growth of solvent crystals starts was crucial for the final properties of the hydrogels.…”

Responsive hydrogels with poly(N-isopropylacrylamide-co-acrylic acid) colloidal spheres as building blocks

“…The introduction of hydrophilic moieties act as side chains or interpenetrating network in PNIPAM hydrogel have been confirmed to increase the deswelling rate by reducing or avoiding the formation of dense skin layer via constructing hydrophilic water diffusion channels [35][36][37][38][39][40][41][42][43]. Introducing dangling PNIPAM chains into PNIPAM hydrogel polymer networks by copolymerization of NIPAM monomers with PNIPAM macromonomers [44][45][46][47][48][49][50][51], by post-crosslinking of PNIPAM chains [52,53], or by using clay sheets as multifunctional crosslinking agents [54][55][56], have also proved to increase the deswelling speed of PNIPAM hydrogels. In those hydrogels, freely mobile dangling PNIPAM chains shrink/swell more rapidly than PNIPAM backbone networks.…”

“…A convenient way is to introduce hydrophilic micro-domains into the network of hydrogels [35][36][37][38][39][40][41][42][43][44]. Another category of chemical modification is to introduce dangling PNIPAM chains into PNIPAM hydrogel polymer networks [45][46][47][48][49][50][51][52][53][54][55][56]. Although those previously reported chemically modified PNIPAM hydrogels deswell faster in response to temperature increase than the normal PNIPAM hydrogels, it still needs more than a few minutes to complete the deswelling process and in some cases the hydrogels need complicated preparation procedure.…”

A novel multi-responsive polyampholyte composite hydrogel with excellent mechanical strength and rapid shrinking rate

“…Other methods, including the use of microporous structure hydrogels prepared by polymerization in the presence of salt [23], sugar [24], oligoethylene glycol [25], hydroxypropyl cellulose [26], or silica particles [27], have been also used. At the same time, nanoparticles incorporating [28,29], freeze-dried [30], nanogel organization [31], and organic-inorganic hybrid [32] can also effectively improve the response rate of hydrogels.…”