An alternative method for long chain branching determination by triple-detector gel permeation chromatography

Gel permeation chromatography with refractive index (RI) or infrared detector (IR), viscometer for intrinsic viscosity (IV) and/or light scattering (LS) has become a prominent technique for quantitative study of polymer long chain branching (LCB). A quantity known as LCB frequency (LCBf) derived from g-factor of Zimm-Stockmayer (ZS) model was here studied and found its problems in reproducibility and accuracy. In this work, an alternative high precision method of the gpcBR approach was used to estimate a more reliable g-factor, called g(est). The branching index, B-factor for number of LCB per molecule was found to be more relevant than LCBf in relating to polymer properties. A proposal is made that enables the distinction between two LCB categories, i.e. branch on main chain and branch on branch. This allows the analysis of these two LCB types on their relative importance to polymer processing and end-use properties. NMR results were obtained in support of the LCB data. (C) 2016 Elsevier Ltd. All rights reserved.