PNIPA dissolves in water, however, when these solutions are heated in above their cloud point temperature, they undergo a reversible lower critical solution temperature (LCST) phase transition from a soluble hydrated state to an insoluble dehydrated state.

[3][4] Furthermore, other molecules in the polymer solution, such as salts or proteins, can alter the cloud point temperature.

[15] The 1980s marked an explosion in interest in PNIPAs with the realization of potential applications due to its unique thermal behavior in aqueous solutions.

Homopolymerization[18] Copolymerization Terpolymerization Cross-linked Hydrogel PNIPA can be functionalized using chain transfer agents using a free radical polymerization.

[18] (1) (2) (3) The versatility of PNIPA has led to finding uses in macroscopic gels, microgels,[19] membranes, sensors, biosensors, thin films,[20][21][22] tissue engineering, and drug delivery.

The tendency of aqueous solutions of PNIPA to increase in viscosity in the presence of hydrophobic molecules has made it excellent for tertiary oil recovery.

[27] When radiolabeled PNIPA copolymers with different molecular weights were intravenously injected to rats, it was found that the glomerular filtration threshold of the polymer was around 32 000 g/mol.

[30] This conversion results in an expulsion of water which causes a physical conformational change, creating a mechanical hinge movement.

Furthermore, PNIPA-based thin films can be applied as nano-switches featuring multiple distinct thin-film states, which is based on the cononsolvency effect.