Chemical structure of poly(N-isopropylacrylamide)

Poly(N-isopropylacrylamide) (variously abbreviated PNIPA, PNIPAAm, PNIPAA or PNIPAm) is a temperature-responsive polymer that was first synthesized in the 1950s.[1] It can be synthesized from NIPAM which is commercially available.

It forms a three-dimensional hydrogel when crosslinked with N,N’-methylene-bis-acrylamide (MBAm) or N,N’-cystamine-bis-acrylamide (CBAm). When heated in water above 32°C, it undergoes a reversible lower critical solution temperature phase transition from a swollen hydrated state to a shrunken dehydrated state, losing about 90% of its mass. In dilute solution, it undergoes a corresponding coil-to-globule transition at similar conditions)[2].. Since PNIPAm expels its liquid contents at a temperature near that of the human body, PNIPAm has been investigated by many researchers for possible applications in tissue engineering [3][4] and controlled drug delivery.[5][6][7] The renal glomerular filtration cut-off of copolymers of PNIPAm is situated around 32,000 g/mol.[8]


  1. ^ Schild, H. G. “Poly(N-isopropylacrylamide): experiment, theory and application” Progress in Polymer Science, 1992, 17 (2), 163–249.
  2. ^ Wu, C; Wang X (1998). "Globule-to-Coil Transition of a Single Homopolymer Chain in Solution". Physical Review Letters 80 (18): 4092–4094. http://ludfc39.u-strasbg.fr/pdflib/polymers/collapse/1998_wu_wang.pdf. Retrieved 25 September 2010. 
  3. ^ von Recum, HA.; Kim, SW. (1998). "Retinal pigmented epithelium cultures on thermally responsive polymer porous substrates". J Biomater Sci Polym Ed 9: 1241–1253. doi:10.1163/156856298X00758. http://www.ingentaconnect.com/content/vsp/bsp/1998/00000009/00000011/art00009?token=004e12baee383a4b3b2570497b607b406a4d2c6b67212a726e2d2954496f642f466f193f105cfe. 
  4. ^ Lee, EL.; von Recum, HA (2010). "Cell culture platform with mechanical conditioning and nondamaging cellular detachment". J Biomed Mater Res A 93: 411–8. http://openurl.ebscohost.com/linksvc/linking.aspx?genre=article&sid=PubMed&issn=1549-3296&title=J%20Biomed%20Mater%20Res%20A&volume=93&issue=2&spage=411&atitle=Cell%20culture%20platform%20with%20mechanical%20conditioning%20and%20nondamaging%20cellular%20detachment.&aulast=Lee&date=2010. 
  5. ^ Chung, J. E.; Yokoyama, M.; Yamato, M.; Aoyagi, T.; Sakurai, Y.; Okano, T. “Thermo-responsive drug delivery from polymeric micelles constructed using block copolymers of poly(N-isopropylacrylamide) and poly(butylmethacrylate)” Journal of Controlled Release, 1999, 62, 115–127. Abstract
  6. ^ Hu Yan and Kaoru Tsujii. “Potential application of poly(N-isopropylacrylamide) gel containing polymeric micelles to drug delivery systems” Colloids and Surfaces B: Biointerfaces. 2005, 46, 142–146. Abstract
  7. ^ Antunes F. , Gentile L. , Tavano L. , Oliviero Rossi C. , " Rheological characterization of the thermal gelation of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)co-Acrylic Acid". Applied Rheology, 2009, Vol. 19, n. 4, pp. 42064-42069. Abstract
  8. ^ Bertrand, N.; Fleischer, J.G.; Wasan, K.M.; Leroux, J.C. (2009) Pharmacokinetics and biodistribution of N-isopropylacrylamide copolymers for the design of pH-sensitive liposomes. Biomaterials, 30, 2598-2605 Abstract