Designed incorporation of semi-crystalline domains into structured latex particles via solvent-aided emulsion polymerization

Despite significant effort, it remains a major challenge to match the mechanical properties of films cast from solvent-based polymers using waterborne polymer dispersions. In this paper, we study an emulsion polymerization route for the designed incorporation of semi-crystalline domains of poly(stearyl acrylate) into structured particles as a way to improve mechanical performance. First, the use of a co-solvent to facilitate the polymerization of stearyl acrylate by emulsion polymerization is demonstrated. It is shown that with as little as 5 wt% of isopropanol (IPA) in the aqueous phase the diffusion limitations that typically hinder polymerization of very hydrophobic monomers are overcome. The solvent-aided approach is then used in the design of seeded semibatch emulsion polymerization reactions using an amorphous poly(styrene-co-butyl acrylate) latex as the seed. This technique allows for the production of kinetically frozen particle morphologies that are shown to be beneficial for the final mechanical properties of films cast from the structured latexes and outperform conventional core-shell type latexes.