The Pressure and Temperature Dependences of the Second Virial Coefficients and the Chain Dimensions of Polydimethylsiloxane Solutions

Publisher Website
Google Scholar
Abstract
A new light-scattering optical cell was designed in order to perform light-scattering measurements at various temperatures and under pressures up to 400 kg/cm2. The second virial coefficients and the radii of gyration were determined at high polymer dilutions for polydimethylsiloxane in cyclohexyl bromide at 27.0, 36.5, 47.2, and 56.2 °C, in benzene and toluene at 27.0 °C, and in chlorobenzene at 30.0 °C. The method employed to determine the dimensions of the polymer is described. By a series of measurements of polydimethylsiloxane solutions, it is shown that the second virial coefficients, the radii of gyration, and the fundamental thermodynamic properties of the solutions depend on the pressure. The correlation between values of A2 and ⟨S2⟩1⁄2 shows that pressure influences these quantities through its effect on the polymer-solvent interaction parameter, χ or z. The values of the relative partial molar excess volume were calculated directly from the data. The obtained data were compared with the excluded volume theories and the corresponding state theories; the agreement was fair.