The Effect of Pressure on the Sol-Gel Transformations of Macromolecules

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Abstract
The effect of pressure on the gelation of macromolecules, such as gelatin, polyvinyl alcohol, and methyl cellulose, was investigated in order to clarify which binding forces contribute to their gel formations. The values for ΔH and ΔV accompanying the gel formation were calculated from the Eldrige-Ferry’s plot and the Clausius-Clapeyron equation respectively. The values for ΔH and ΔV in the gel fromations of gelatin and polyvinyl alcohol are both negative, while those in methyl cellulose are both positive. From the thermodynamical considerations, it has been found that the formation of hydrogen bonds results in negative values of ΔV Fand ΔH, while that of hydrophobic bonds results in positive values of ΔV and ΔH. Therefore, it may be assumed that the main binding forces in the gelations of gelatin and polyvinyl alcohol may be attributed to hydrogen bonds, and that those in methyl cellulose may be attributed to hydrophobic bonds, at least up to 6000 atm.