Partitioning of Functional Monomers in Emulsion Polymerization: Distribution of Carboxylic Acid and Hydroxy (Meth)acrylate Monomers between Water and Polymers

Abstract

We have studied the distribution of vinyl acid and hydroxy (meth)acrylate monomers between water and a variety of styrene, acrylate, and methacrylate homopolymers and copolymers. From equilibrium distribution data, we determined the Flory–Huggins monomer–polymer interaction parameters (χ) using appropriate water phase activity coefficients (γ). For the functional monomers studied here, their χ values with (meth)acrylic polymers are all below 0.5 and are often negative. Those with polystyrene are greater than 0.5. This comparison highlights the influence of hydrogen bonding on the water–polymer phase distribution in latex systems. Within functional monomer concentration ranges typical in emulsion polymerization, we find both the χ values and distribution coefficient to be linearly correlated with the molar volume of the polymer. With proper χ and γ values, the complete distribution across all phases for functional monomers can be determined, both for single-component systems as well as for multimonomer and copolymer environments.