Poly(N-isopropylacrylamide) is a water-soluble polymer that switches from an extended coil to a collapsed globule near 32 degrees Celsius. The transition is sharp because the amide group and the isopropyl group have competing affinities for water, and it reverses on cooling [1]. Grafted layers change thickness across the transition, which makes the surface hydrophilicity switchable [2]. In a crosslinked network the same transition produces a volume change of an order of magnitude [3]. Copolymerization shifts the transition temperature, and the shift depends on the comonomer rather than on the molecular weight [4]. Under hydrostatic pressure the transition broadens and moves, which complicates the use of the polymer as a calibrated temperature probe [5].
- lower critical solution temperature
- thermoresponsive polymer
- coil-globule transition
- hydrogel
- phase separation
- copolymerization
- swelling ratio
References
- Ohya, S.; Kidoaki, S.; Matsuda, T.; Poly(N-isopropylacrylamide) (PNIPAM)-grafted gelatin hydrogel surfaces: interrelationship between microscopic structure and mechanical property of surface regions and cell adhesiveness. Biomaterials 2005, 26, 3105-3111, 10.1016/j.biomaterials.2004.08.006.
- Kim, G.; Jung, Y.; Cho, K.; Lee, H.J.; Koh, W.G.; Thermoresponsive poly(N-isopropylacrylamide) hydrogel substrates micropatterned with poly(ethylene glycol) hydrogel for adipose mesenchymal stem cell spheroid formation and retrieval. Materials Science and Engineering: C 2020, 115, 111128, 10.1016/j.msec.2020.111128.
- Cheng, Q.; Mandsberg, N.K.; Levkin, P.A.; Hsu, S.; UV‐Induced Photopatterning of the Thermoresponsive Properties of a Poly(ethylene glycol)methylether acrylate‐co‐poly(N‐isopropylacrylamide) Hydrogel. Small Structures 2025, 6, 2400560, 10.1002/sstr.202400560.
- Mambiri, L.T.; Guillory, R.; Depan, D.; Thermoresponsive Behavior, Degradation, and Bioactivity of Nanohydroxyapatite on Graphene Oxide Nanoscroll-Enhanced Poly(N-isopropylacrylamide)-Based Scaffolds. Polymers 2025, 17, 2014, 10.3390/polym17152014.
- Papadakis, C.M.; Niebuur, B.J.; Schulte, A.; Thermoresponsive Polymers under Pressure with a Focus on Poly(N-isopropylacrylamide) (PNIPAM). Langmuir 2024, 40, 1-20, 10.1021/acs.langmuir.3c02398.