The state of water in thermoresponsive poly(acryloyl- l-proline methyl ester) hydrogels observed by DSC and 1H-NMR relaxometry

• Published in: Radiation physics and chemistry (Oxford, England : 1993) England : 1993), 1999-06, Vol.55 (2), p.209-218
• Main Authors: Carenza, Mario, Cojazzi, Gianna, Bracci, Barbara, Lendinara, Laura, Vitali, Lina, Zincani, Michele, Yoshida, Masaru, Katakai, Ryoichi, Takacs, Erzsebet, Higa, Olga Z., Martellini, Flavia
• Format: Article
• Language: English
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/S0969-806X(98)00328-4

Hydrogels that reversibly swell or shrink in water with decreasing or increasing temperature, respectively, were obtained by γ ray-induced polymerization of acryloyl- l-proline methyl ester in the presence of different amounts of a crosslinking agent. The role of water in the hydrated polymers was investigated by DSC and 1H-NMR relaxometry. From the curves of fusion of water determined by the former it was possible to ascertain that the amount of both freezing and non freezing water decreased with increasing the crosslinker percentage and/or swelling temperature. Moreover, at the temperatures higher than 37°C, the water absorbed by the different hydrogels is mostly present as non freezing water. The 1H-NMR relaxometry study enabled the spin–spin and spin–lattice relaxation curves to be analyzed. It was possible to distinguish three “populations” of protons and identify two of them with protons of freezing and non freezing water determined by DCS.