In this work, we investigated the behavior of poly(dimethylsiloxane-co-diphenylsiloxane)s under good and theta solvent conditions by using turbidimetry and viscosimetry. The evolution of the optical properties as a function of the solvent quality allowed the composition of the methylbenzene/methanol mixtures at the theta point to be determined. The intrinsic viscosity was determined in good (methylbenzene) and theta (methylbenzene/methanol) solvents at T = 298 K using different approaches. The unperturbed dimension parameters were calculated and are discussed as a function of copolymer composition. The introduction of the diphenylsiloxane units into a poly(dimethylsiloxane) chain results in an increase in the unperturbed dimensions as a consequence of the decrease in chain flexibility.

The Behavior of Poly(dimethylsiloxane-co-diphenylsiloxane)s in Good and Theta Solvents

Miscibility of polyvinylchloride and polychloroprene blends: Viscometric and light scattering studies of dilute solutions

In this work we investigate the effect of the solvent quality on the thermodynamic behavior of the polydimethyldiphenylsiloxane copolymer by using turbidimetry and viscosimetry. The turbidimetric method was used for the determination of the composition of the solvent mixture at the theta point. The experimental data obtained by using the capillary viscometry both in good and theta solvent conditions have been processed by using classical Huggins equation and new Wolf model (2007), which allows the calculation of intrinsic viscosities and other hydrodynamic parameters. The results obtained by using the two approaches were discussed comparatively. The conformational properties of copolymer in solution depend on their molecular structure, which is essentially dominated by the solvent quality, reflecting the balance of the interactions between the polymer chains and each solvent and that between solvent molecules.

Influence of the Solvent Quality on the Thermodynamic Behavior of Polymethylphenylsiloxane Solutions

It is well recognized that a polymer is under theta conditions if the second virial coefficient A2 is zero and the mean square radius of gyration of the polymer is proportional to the square root of its molecular weight. For any single solvent or a mixture of solvents, this condition prevails at a certain temperature, the theta temperature. Here, the polymer chains are said to be unperturbed as they are not affected by long-range interactions. In this note we report the theta composition for chlorosulfonated polyethylene (CSP) in a solvent-nonsolvent mixture, viscometric data under theta conditions, and the expansion coefficients. Different theoretical expressions are also examined in terms of the present data.

S. Saha

Papers

Dilute-Solution Properties of Chlorosulfonated Polyethylene. Il Theta Composition and Expansion Coefficient