Quantitative assessment of polymer molecular shape based on changes in the slope of the Mark-Houwink plot derived from size-exclusion chromatography with triple detection

A new approach is presented for gaining additional insights from the molecular weight distribution and intrinsic viscosity of polymers as obtained using size-exclusion chromatography in combination with refractive index, viscometry, and multiangle light scattering detectors. The approach allows for a more quantitative interpretation of the Mark-Houwink plot by assessing the variation of the slope as a function of molecular weight. No prior information on the inter- and intramolecular interactions of the polymer is needed. The proposed curvature parameter can be correlated to the structural and chemical properties (e.g., branching, composition, randomness) of the polymer. The influence of the covered molecular weight interval and the sample concentration on the precision of the method was studied. This new workflow can be utilized to assess the effect of the solvent system and conditions on the solvation behavior of polymers. To evaluate the applicability of the workflow, three case studies have been performed, including an analysis of ethylene-propylene-diene monomer, cellulose ether, and polyamide-4,10 samples. In addition, an open-access tool is provided, to aid polymer researchers in incorporating this approach in their work. The developed method can be used to quickly investigate whether an industrial polymer batch contains unwanted branched species or exhibits particular solvation behavior.