Biobased latexes from natural oil derivatives

Abstract

Vinyl aromatic monomers derived from dihydroeugenol (EBM) and guaiacol (GBM) were copolymerized, via a miniemulsion process, with aliphatic monomers from high oleic soybean oil (HOSBM), yielding emulsion polymers with higher levels of biobased content. This fully renewable monomer feed generated a broad range of novel latexes, with the number-average molecular weight varying from 25,000–650,000 g/mol. Increasing the content of aromatic biobased monomers heightened the resulting latexes’ molecular weights due to the decreasing unsaturation degree (lower HOSBM content) in the reactive mixture. The monomer feed unsaturation effect was found to be more pronounced for latexes derived from EBMs and HOSBMs because EBMs are more reactive in free radical polymerization compared to GBMs. The presence of oil-derived unsaturated fragments in emulsion polymers provides an opportunity to crosslink resulting latexes in a controlled way to adjust the polymer networks’ thermomechanical properties. Thus, crosslinked films and coatings from latexes made of 25–90 wt.% EBM/GBM and 10–75 wt.% HOSBM were tested. This demonstrated that the characteristics of the resulting biobased latex materials are determined by the nature and ratio of the aliphatic oil residues from HOSBM and the aromatic fragments from EBM/GBM in the macromolecular backbone. Young’s modulus was also higher for the films with greater levels of EBM/GBM, while flexibility of the resulting polymeric materials was found to be determined by soft oil-derived copolymer content. For all films, hardness, impact resistance and adhesion to the steel substrate were evaluated. By combining the aliphatic fatty acid fragments of HOSBM with the aromatic EBM/GBM structure, durable latexes can be synthesized, with the ability to balance the thermomechanical properties of latex polymer networks over a broad range.