Light‐scattering Characterization of the Molecular Weight Distributions of Some Intractable Polymers

Abstract

Recent developments of using laser light scattering (LLS) to characterize the molecular weight distribution f(M) of special polymers such as Kevlar, Tefzel, Teflon, branched epoxy clusters, gelatin, dextran, segment copolymers and polymer mixtures, are reviewed. The basic principle of combining static (classic) and dynamic LLS results is outlined. In dynamic LLS, the line-width (or the translational diffusion coefficient) distribution G(Γ) can be obtained from the precisely measured intensity–intensity time correlation function. The key problem is transforming G(Γ) to a corresponding molecular weight distribution f(M) is to establish a calibration between D (the translational diffusion coefficient) and M. Typical examples were used to illustrate different calibration methods, including the methods of using a series of narrowly distributed polymer standards with different molecular weights, using two or more broadly distributed polymer samples, and one broadly distributed polymer samples plus an additional experimental method (e.g. viscometry or size exclusion chromatography). The advantages and disadvantages of the LLS method are discussed by comparison with size exclusion chromatography. © 1997 John Wiley & Sons, Ltd.