Molar mass distributions in homopolymer blends from multimodal chromatograms obtained by Sec/Gpc with a concentration detector

This article proposes data treatment for estimating the individual (and unimodal) molar mass distributions (MMDs) of each polymer component in a blend from multimodal concentration chromatograms obtained by size exclusion chromatography (SEC/GPC). The Differential Refractometer (DR) chromatograms are deconvoluted into linear combinations of exponentially-modified Gaussian distributions. The deconvolutions are possible if the individual peaks are not fully overlapped and if the mass fractions of the minor components are not too low. To help determine the number and approximate location of the individual peaks, the second derivative of the chromatogram is employed. For blends of chemically identical homopolymers, the deconvolution stage directly provides the mass fractions of the individual peaks. For blends of two chemically different homopolymers, the chemical composition and detector responses of the individual components must be determined, for example with the help of dual detection (UV/DR). The procedure was validated with blends of a priori known components.