| Vegetable Oil Macromonomers (VOMMs) have been shown to be an attractive intermediate for volatile organic compound (VOC) reduction in architectural coatings. The main advantage of VOMM technology is the temporary plasticization effect of the fatty acid chains with the potential for crosslinking after the film is formed. However, VOMM incorporation in conventional emulsions is challenging because its hydrophobicity restricts its diffusion through the aqueous phase. Miniemulsion polymerization has been widely used to incorporate highly hydrophobic monomers. Diffusion limitations are avoided by polymerizing inside the monomer droplets, but to ensure this, droplet stabilization is required. A soybean oil-based VOMM was evaluated as a copolymerizable hydrophobe in miniemulsion polymerization of BA/MMA. Monomer droplets were stabilized prior to polymerization, and a coagulum-free miniemulsion was obtained. Gel content studies indicated that a crosslinked network was formed upon drying of the film. This method permitted incorporation of 35% VOMM into the polymer backbone.;VOMM hydrophilicity was improved by incorporating ethoxylate groups. Fatty acid surfactants with different ethoxylate lengths were acrylated and used as model macromonomers for this study. Monomer diffusion through the water phase was investigated by monitoring particle size, residual monomer, and heat evolution throughout the polymerization using dynamic laser light scattering, GC, and RC-1e respectively. Photo-DSC and reaction calorimetry were used to determine extent of chain transfer. RC-1e proved to be a useful technique to determine incorporation of unsaturated macromonomers in emulsion polymerization. Macromolecules with lower hydrophobicity incorporated better in conventional emulsion polymerization and no special technique was needed to obtain coagulum-free latexes and glossy films. Specifically, for acrylated fatty acids, an average ethoxylate chain of 10 units was sufficient to facilitate diffusion through the aqueous phase. |
