Features of Highly Hydrophobic Plant Oil-Based Vinyl Monomers in Cationic and Free Radical Polymerization
View/ Open
Abstract
The demand for polymeric materials, which have traditionally been produced from petroleum-based resources over the last century, continues to grow each year. However, the supply of fossil fuels is limited. This, along with price volatility, harmful effects on the environment, and stricter regulations, have led to a surge in the exploration of suitable replacements, namely renewable resources such as plant and vegetable oils. In this work, newly synthesized highly hydrophobic plant oil-based vinyl monomers were polymerized using different mechanisms and processes to obtain polymer coatings and crosslinked films. First, novel vinyl ether monomers derived from soybean oil were copolymerized with vinyl ether counterparts derived from poly(ethylene glycol) (PEG) via cationic polymerization to prepare alkyd-type coatings. Soybean oil-derived polymer coatings and free films were formed by autoxidation of the unsaturation provided by the parent soybean oil moieties. Studies revealed that mechanical and viscoelastic properties, hydrophobicity, and morphology of coatings were dependent on copolymer composition and even more strongly on molecular weight and molecular weight distribution. The soybean oil-derived polymer coatings exhibited Tg values below room temperature, and it was shown that their thermomechanical properties were dependent on crosslink density. Next, plant oil-based acrylic monomers (POBMs) from soybean, high oleic soybean, and olive oils were copolymerized with styrene, methyl (meth)acrylate, and vinyl acetate to yield latexes and prepare polymer films with tailorable thermomechanical properties. Feasibility of the emulsion process was realized with regard to parent plant oil structure (unsaturation amount), POBM content and comonomer aqueous solubility, by determining copolymerization kinetics, mode(s) of latex particle nucleation, and molecular weight of resulting latex copolymers. POBM-emulsifier interactions, competing modes of latex particle nucleation, and effect of comonomer radical reactivity have all been investigated. Total monomer conversion and molecular weight of latex copolymers were enhanced by incorporation of an amphiphilic oligosaccharide (methyl-β-cyclodextrin) within the reaction system, which increases the availability of the POBMs and simultaneously diminishes degradative chain transfer reactions that are triggered by POBM fatty acid unsaturation fragments.