Toward Understanding the Architecture (Branching and MWD) of Crosslinked Acrylic Latexes

The architecture of crosslinked acrylic latexes of 2-ethylhexyl acrylate, methacrylic acid, and a crosslinker agent are investigated. These polymers contain a significant amount of gel content. Branching is obtained by liquid- and melt-state 13C NMR spectroscopy. For the first time, the branching densities (long and short chains) of the soluble and gel fractions are measured independently. Branching is higher for the polymers produced with the most-efficient crosslinkers, namely those which yield a higher crosslinking density. The branching (long chains) and the molecular-weight distribution (MWD) of the soluble fraction are characterized by size-exclusion chromatography (SEC) coupled with triple detection. Coelution of branched chains at large elution volumes is observed in the SEC chromatograms indicating the highly branched nature of the sol fractions of the latexes.