ERROS IN THE MOLECULAR CHARACTERIZATION OF BRANCHED POLYMERS BY SIZE EXCLUSION CHROMATOGRAPHY WITH MOLAR MASS DETECTORS

CLEMENTI, LUIS A.; VEGA, JORGE R.; MEIRA, GREGORIO R.

Buenos Aires

Simposio; X Simposio Argentino de Polímeros; 2013

Universidad de Buenos Aires, Universidad Nacional de La Plata, INTI e ITBA

This theoretical article 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 detectors. First, the ideal SEC fractionation of a polymer with up to 75 branches per molecule was simulated, by assuming a -solvent, perfect fractionation by hydrodynamic volume (except for a minor mixing in the detector cells), and noise-free measurements. Under such ideal conditions, the MMD is acceptably determined, while the branching distribution is only approximately estimated. Then, a more realistic simulation was attained by including band broadening in the column, noise in the measurements, and the analysis with a good solvent. Under low measurement noises, the estimated MMD remains essentially unbiased. In contrast, due to theoretical uncertainties and many sources of errors, only a gross estimate of the instantaneous degree of branching is possible.