Characterization of hydrosoluble fraction and oligomers in poly(vinylidene chloride) latexes by capillary electrophoresis using electrophoretic mobility modeling

Abstract

The characterization of hydrosoluble oligomers in latexes is an important topic in emulsion polymerization since oligomers are suspected to be responsible for latex destabilization. In this work, the hydrosoluble fraction of poly(vinylidene chloride) latexes synthesized by emulsion polymerization of three monomers (acrylic acid, methyl acrylate, vinylidene chloride) was characterized by capillary electrophoresis (CE). CE using direct UV detection permitted to estimate residual monomers and surfactants concentrations contained in the latexes serums. Water soluble oligomers, polymerization initiator (persulfate) and other inorganic anions were detected by indirect UV detection. The oligomers content in the dry extract of serum was estimated to be about 6% (% m/m) represented mainly by 9 different compounds belonging to 3 different families. Using a semi-empirical electrophoretic mobility modeling, the charge number of these oligomers was estimated to be −2 and the molar masses were estimated in the range of ∼300–550 g.mol−1. Oligomer samples obtained by surfactant-free polymerization, with different initial monomers proportions, provided qualitatively 14 different oligomers, including the 9 oligomers previously detected in the serums. Finally, the latex was characterized (electrophoretic mobility and zeta potential) using its serum as a background electrolyte. This approach could be very useful to study the behavior of the latexes, and possibly destabilization effect, in analytical conditions very close to its real environment / applications.