Effects of Pressure on Thermal Response of Poly-(N-vinyliso-butyramide) (PNVIBA)

摘要

There are several known synthetic polymers~1 that carry both hydrogen bonding properties and hydrophobic interactions in aqueous solutions and they show more or less distinct changes in their molecular level states (coil-to-collapse, in solution)~2 and volume phase transitions (in gel form)~3. Last year we showed~4 that the aqueous solutions of poly(N-vinylisobutyramide) (PN VIBA)~5,6 exhibited characteristic pressure-temperature behavior, similar to another thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM). Near atmospheric pressure, the transition temperature increased with increasing pressure, but, at pressure, higher than 150 MPa, it decreased with increasing pressure to give the apparent turning point in the T-P diagrams. They were explained by the thermodynamic equation proposed by Hawley~7 for the pressure- and temperature-induced denaturation of proteins and the results implied the possibility of studying these polymers as synthetic models of so-called cold denaturation of proteins in reversible manner.