The features of emulsion copolymerization for plant oil-based vinyl monomers and styrene

Vinyl monomers from plant oils that have different degrees of unsaturation, soybean (SBM), and olive (OVM) oil were copolymerized in emulsion with styrene to investigate the kinetics features and feasibility of latex formation. In the presence of up to 20 wt% of SBM/OVM in the initial feed, the order of reaction with respect to the emulsifier and initiator do not depend on the plant oil-based monomers’ unsaturation degree. Reaction kinetics agree with the Smith-Ewart theory, predicting that the number of nucleated latex particles is proportional to the surfactant and initiator concentration to the powers 0.6 and 0.4, respectively. Copolymerization of styrene with plant oil-based monomers follows the typical phenomenology for emulsion polymerization of hydrophobic monomers with a micellar nucleation mechanism. Nevertheless, based on experimentally obtained latex particles’ size and number, evidence for a mixed mode of nucleation (both micellar and homogeneous) was observed in this research. Mixed nucleation can be explained by the potential surface-active properties of plant oil-based monomer molecules containing polar acryloylamino “head,” CH2CHC(O)NH and hydrophobic “tail,” C17). Because of the effect of the degradative chain transfer on the plant oil-based monomer, the molecular weight of the resulting macromolecules decreases as the monomer degree of unsaturation and monomer fraction in the initial mixture increases. This feature can be used for controlling the molecular weight of latex polymers that come from plant oil-based monomers by varying the content and nature of bio-based monomer in feed. The thermomechanical properties of latex films depend considerably on the nature and amount of incorporated plant oil-based fragments. Their presence lowers Tg (more than 40 °C difference) and provides some flexibility and toughness as compared to the normally rigid and brittle polystyrene.