Versatile Platform for Controlling Properties of Plant Oil-Based Latex Polymer Networks

A series of latexes from acrylic monomers (made from olive, soybean, linseed, and hydrogenated soybean oils), significantly different in terms of fatty acid unsaturation, were synthesized using miniemulsion copolymerization with styrene. The number-average molecular weight and the glass transition temperature of the resulting copolymers with high levels of biobased content (up to approximately 60 wt %) depend essentially on the amount of unsaturation (the number of double bonds in triglyceride fatty acid fragments of plant oil-based monomers) in the reaction feed. When plant oil-based latex films are oxidatively cured, the linear dependence of the cross-link density on reaction feed unsaturation is observed. Dynamic mechanical and pendulum hardness measurements indicate that the properties of the resulting plant oil-based polymer network are mainly determined by cross-link density. On the basis of the linear dependence of the cross-link density on monomer feed unsaturation, it can be concluded that the latex network formation and thermomechanical properties can be adjusted by simply combining various plant oil-based monomers at certain ratios (“given” unsaturations) in the reaction feed. Assuming a broad variety of plant/vegetable oils available for new monomers synthesis, this can be considered as a promising platform for controlling properties of plant oil-based latex polymer networks

Free Radical Polymerization Behavior of the Vinyl Monomers from Plant Oil Triglycerides

A one-step method of plant oil direct transesterification was used to synthesize new vinyl monomers from sunflower (SFM), linseed (LSM), soybean (SBM), and olive (OVM) oils. The degree of unsaturation in plant oil fatty acids was used as a criterion to compare the free radical polymerization behavior of new monomers. The number-average molecular weight of plant oil-based homopolymers synthesized in toluene in the presence of AIBN at 75 °C varies at 11 000–25 000 and decreases as follows: poly­(OVM) > poly­(SFM) > poly­(SBM) > poly­(LSM), corresponding to increasing degree of unsaturation in the monomers. Rate of polymerization depends noticeably on the degree of unsaturation in monomers. Due to the allylic termination, chain propagation coexists with effective chain transfer during polymerization. The obtained values of <i>C</i>_M (ratio of chain transfer and propagation rate constants) depends on monomer structure as follows: <i>C</i>_M(LSM) > <i>C</i>_M(SBM) > <i>C</i>_M(SFM) > <i>C</i>_M(OVM). ¹H NMR spectroscopy shows that the fraction of the reacting allylic atoms does not vary significantly for the synthesized monomers (7–12%) and is determined entirely by plant oil degree of unsaturation. The glass transition temperature of homopolymers [<i>T</i>_g = 4.2 °C for poly­(SFM), <i>T</i>_g = −6 °C for poly­(SBM)] from new monomers indicates that varying biobased fragments in copolymers might considerably change the intermolecular interactions of macromolecules and their physicochemical properties