Effect of solvent on the optical behavior of macromolecules in a laminar flow

Abstract

Abstract The segmental anisotropy of a series of macromolecules in different solvents was measured by means of streaming birefringence and viscosity. It is shown that the measured segmental anisotropy (α 1 — α 2 ) substantially depends on properties of the solvent applied. Analysis of experimental data leads to an assumption that in the vicinity of polymer chains an ordered disposition of solvent molecules (short‐range order) occurs, contributing a value (α 1 — α 2 ) s to the measured anisotropy. The magnitude of this contribution depends on the optical anisotropy of solvent molecules and their orientation relative to the macromolecule. Thus the actual segmental optical anisotropy (α 1 — α 2 ) K can be evaluated in an isotropic solvent only. Comparison of (α 1 — α 2 ) K with the value of (α 1 — α 2 ) obtained for the macromolecule in an anisotropic solvent gives (α 1 — α 2 ) s . It follows from the estimation that in spite of a strong solvent effect on the measured segmental anisotropy, the actual mutual orientation of solvent‐solute molecules is rather low. It is also shown that the short‐range order is particularly pronounced in systems where polymer‐solvent interactions are favored in comparison to polymer‐polymer and solvent‐solvent interactions.