Formation and Control of Higher-order Functional Structures of Biomodel Polymers

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The physicochemical properties of the phase-transition of so-called themoresponsive synthetic polymers have been widely studied. We have investigated the effects of pressure on their behavior and showed that the pressure effects were highly interactive with the effects of inert salts, and that these results can be generally explained in terms of hydration and dehydration processes. The apparent transition properties and light scattering behavior of these polymers upon a variation in pressure and temperature are common to a number of other water-soluble bio-related polymers, from elastin model peptide to the dilute solutions of hydroxypropyl cellulose(HPC).In this project, we investigated the effects of pressure on the phase behavior of elastin model peptide((VPGIG)_<40>), and thermoresponsive vinyl polymers in dilute aqueous solutions. We found that pressure strongly affects the dissolution temperature and the light-scattering properties in this concentration range, and that the pressure effects are strongly interactive with added inert salts.Commonly the transition temperature(Tt), as measured by apparent light scattering, increased with an increase in pressure at lower pressures, but decreased with increasing pressure above 100-150 MPa. At lower temperatures, the transition pressure(Pt)of some polymers increased slightly with increasing temperature, but decreased with at temperatures above 10-15 ℃, as a result they showed elliptic phase diagrams.Both the Tt and the Pt showed strong concentration dependence on inert salt ; the Tt and the Pt decreased with increasing concentrations of salting-out ions such as KCl and K_2SO_4, whereas the addition of salting-in ions such as KI or KSCN increased the Tt and Pt.Based on these results, a general explanation of the elliptic phase diagram in similar systems has been elucidated.