Emulsion polymerization of plant oil-based acrylic monomers: Resourceful platform for biobased waterborne materials

Synthesis of monomers and polymers based on plant/vegetable oils has gained much attention due to their biocompatibility, non-toxicity, and renewability. In some polymeric materials and applications plant oil-based polymers can successfully replace conventional commodity counterparts from petroleum resources. In this regard, we developed a one-step process for the synthesis of a series of acrylic monomers by direct transesterification of significantly different in terms of fatty acid unsaturation plant oil triglycerides with N-(hydroxyethyl)acrylamide. The reactivity of resulted plant oil-based monomers (POBMs) in free radical polymerization is primarily determined by the acryloylamide moiety of POBM. However, the presence of various unsaturated fatty acid fragments in POBMs causes the chain transfer reactions due to the abstraction of the allylic hydrogen atoms during polymerization. While mechanism of emulsion copolymerization of POBMs with styrene agrees with the Smith-Ewart theory (indicating micellar nucleation of latex particles), the POBMs copolymerization with more water-soluble monomers (methyl methacrylate and vinyl acetate) proceeds through mixed particle nucleation mode (micellar and homogeneous). The number-average molecular weight and the T_g of the resulting latex copolymers with high levels of biobased content (up to 70 wt%) depend essentially on the amount of unsaturation (number of double bonds in triglyceride fatty acid fragments) in the monomer feed. When plant oil-based latex films are oxidatively cured, the linear dependence of the crosslink density on reaction feed unsaturation is observed. It indicates that the properties of the resulting polymer networks (coatings), being determined by crosslink density, can be controlled by monomer feed ration and POBMs content in the feed.