Thermoreversible gelation of isotactic-rich poly(N-isopropylacrylamide) in water

• Published in: The Journal of chemical physics Vol. 135; no. 11; p. 114903
• Main Authors: Nakano, Shinya, Ogiso, Takao, Kita, Rio, Shinyashiki, Naoki, Yagihara, Shin, Yoneyama, Masaru, Katsumoto, Yukiteru
• Format: Journal Article
• Language: English
• Published: United States 21.09.2011
• ISSN: 1089-7690
• DOI: 10.1063/1.3637943

We report the experimentally determined phase diagram for an aqueous solution of isotactic-rich poly(N-isopropylacrylamide) (PNiPAM) composed of the sol-gel transition curve and the cloud-point curve. The meso diad content of isotactic-rich PNiPAM is 64%, and it is soluble in water at low temperatures, but undergoes a sol-to-gel transition with increasing temperature in the investigated concentration range of 1.8 wt. %-6.0 wt. %. With a further increase in temperature, the system becomes turbid. The gel formation and clouding behavior are thermally reversible. This is the first observation of thermoreversible gelation under the cloud-point temperature for an aqueous solution of PNiPAM. On the basis of the determined phase diagram, we carried out light scattering experiments to characterize the sol-gel transition behavior as a function of temperature.