| Version | Summary | Created by | Modification | Content Size | Created at | Operation |
|---|---|---|---|---|---|---|
| 1 | Jack Zhong | -- | 131 | 2026-10-21 09:33:30 | | | |
| 2 | Jack Zhong | -9 word(s) | 122 | 2026-10-21 09:34:06 | | |
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].