Feasibility of determination of heterogeneity in copolymer composition by light scattering

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Abstract
The sensitivity of the light‐scattering method for the determination of the composition heterogeneity of copolymers is discussed in terms of the accuracy of measurements of the intensity of scattered light. When the composition is independent of molecular weight, a nomographic solution has advantages. The nomograph is used to investigate the feasibility (a) of the determination of heterogeneity by a single measurement at zero refractive index increment of the copolymer and (b) of the determination of the heterogeneity from two measurements. The results show that in the case of low heterogeneities the light‐scattering method can be used only at higher molecular weights. By using the heterogeneities calculated elsewhere, the possibility of determining them for the individual types of copolymers is discussed. It appears that reported discrepancies between measured and calculated heterogeneities are mostly found in cases where the sensitivity of the light‐scattering method for the determination of the composition heterogeneity is low.