Solution properties of poly(dimethyl siloxane)

Abstract

Abstract The solution properties of poly(dimethyl siloxane) (PDMS) were studied with light scattering (LS), gel permeation chromatography/light scattering (GPC/LS), and viscometry methods. PDMS samples were fractionated, and the weight-average molecular weights, second virial coefficient, and the z-average radius of gyration of each fraction were found according to the Zimm method with the LS technique. In this work, the molecular weight range studied was 7.5 ? 104 to 8.0 ? 105. Molecular weights and molecular weight distributions were determined by GPC/LS. The intrinsic viscosities of these fractions were studied in toluene at 30 °C, in methyl ethyl ketone (MEK) at 20 °C, and in bromocyclohexane (BCH) at 26 °C and 28 °C. The Mark?Houwink?Sakurada relationship showed that toluene was a good solvent, and MEK at 20 °C and BCH at 28 °C were ? solvents for PDMS. The unperturbed dimensions were calculated with LS and intrinsic viscosity data. The unperturbed dimensions, expressed in terms of the characteristic ratio, were found to be 6.66 with different extrapolation methods in toluene at 30 °C. ? 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2678?2686, 2000