Errors in the Molecular Characterization of Branched Polymers by Size Exclusion Chromatography with Molar Mass Detectors

CLEMENTI, L.; VEGA, J. R.; MEIRA, G. R.

Buenos Aires

Simposio; X Simposio Argentino de Polímeros (SAP 2013); 2013

UBA

This article theoretically evaluates the biases introduced into the distributions of molar masses (MMD) and number of long chain branches per molecule (LCBD), when randomly-branched polymers are analyzed by size exclusion chromatography (SEC) with molar mass-sensitive detectors. The MMD of a tetrafunctionally-branched polymer with up to 75 branch units per molecule was simulated and calibrations for the branched classes were estimated from the calibration for the linear class. An ideal SEC model was simulated with perfect measurements and perfect fractionation by hydrodynamic volume, except for a minor mixing in the detector cells. The estimated MMD exhibits a negligible bias, with the local dispersity reaching a maximum of 1.0035 at high molar masses. With perfect measurements and band broadening in the column, the MMD still remains essentially unbiased. In contrast, poor MMD estimates are obtained when minor random noises are added. Only gross estimates of the LCBD are possible.