Abstract
AbstractA procedure is described for estimating unperturbed molecular dimensions from data obtained in “nonideal” solvents. A knowledge of [η], M, and A2 is required. This should be particularly useful for high melting crystalline polymers, since for these polymers a direct determination by light scattering measurements performed under Flory θ conditions is complicated by the tendency of the polymer to crystallize from solution as the solvent becomes thermodynamically poorer. The intrinsic viscosity at θ, [η]θ, is calculated from the semi‐empirical relation: where Γ2 = A2M. The unperturbed dimensions are then calculated through use of the relations appearing in Flory's treatment of intrinsic viscosity: Unperturbed dimensions calculated in this manner for polyisobutylene and polystyrene compare favorably with values directly measured by light scattering. This procedure is used to estimate the unperturbed dimensions of polyethylene, 6,6‐nylon, polyethylene terephthalate, and polyacrylonitrile. A comparison of the relative chain stiffness of these polymers allows some interesting correlations with Flory's theoretical treatment of semi‐flexible chain molecules.
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