Monitoring the evolution of the microstructure of vinyl silane monomer containing poly(vinyl acetate) based copolymer latexes during storage

Asymmetric-Flow Field-Flow Fractionation of complex waterborne polymer dispersions: Effect of the concentration of water in the measurement of molar mass distributions

Asymmetric-Flow Field-Flow Fractionation is a very powerful technique for measuring the molar mass distribution of polymers with complex microstructures. The analysis of some samples such as self-crosslinkable latexes requires to directly dissolve the polymer dispersion in the eluent (THF) without drying it, and this work studies the effect of the presence of this water in those analysis. Taking a polystyrene latex as model system, it was observed that the measured molar mass and radius of gyration increased as the concentration of water in the sample increased. This was an effect of a decrease in the compatibility between the solvent mixture (THF and water) and the polymer, which formed aggregates, and could be predicted calculating the polymer-solvent interaction parameter. When the study was extended to poly(methyl methacrylate), poly(n-butyl acrylate) and poly(vinyl acetate) the same general trend was observed, however, the impact of the water was less significant as the hydrophilicity of the polymer increased. Most importantly, if the samples with the highest water content were first dissolved in THF and afterwards dried using MgSO₄ the measured molar mass and radius of gyration values were the same as for the reference sample (dried in the oven), providing a method to analyze samples that cannot be dried into a film and remove the negative effect of the water at the same time.