Free-Radical Copolymerization Behavior of Plant-Oil-Based Vinyl Monomers and Their Feasibility in Latex Synthesis

Abstract

Vinyl monomers from soybean, sunflower, linseed, and olive oils were copolymerized with styrene (St), methyl methacrylate (MMA), and vinyl acetate (VAc) to determine the reactivity of biobased monomers in radical copolymerization, as well as their feasibility in emulsion processes for the synthesis of biobased latexes. Radical copolymerization of plant-oil-based monomers is described with the classical Mayo–Lewis equation. Using emulsion (or miniemulsion) polymerization with MMA or VAc, stable aqueous polymer dispersions with latex particles measuring 80–160 nm and containing 3–35 wt % of biobased monomer units were successfully synthesized. The number-average molecular weight of the latex copolymers (20 000–150 000) decreases by increasing the degree of unsaturation in monomers and their content in the reaction feed. The presence of plant-oil-based fragments changes the T g of resulting copolymers from 105 to 79 °C in copolymerization with MMA and from 30 to 11 °C in copolymerization with Vac. As a result, biobased units provide considerable flexibility (elongation at break of about 250%) and improve the toughness of the normally rigid and brittle poly(MMA). Even a small amount (2–5%) of biobased fragments incorporated into the structure of poly(VAc) significantly improves water resistance and provides hydrophobicity to the resulting polymer latex films. The obtained results clearly indicate that the vinyl monomers from plant oils can be considered as good candidates for internal plasticization of polymeric materials through reducing intermolecular interactions in copolymers.

Plasticizing and Hydrophobizing Effect of Plant OilBased Acrylic Monomers in Latex Copolymers with Styrene and Methyl Methacrylate

“…When long unsaturated fatty acid fragments (C18) of POBMs are incorporated into the macromolecules, they can reduce the intermolecular interactions and increase intermolecular distance, thus increasing chain mobility and facilitating polymer softening (plasticizing). Suitability of POBMs in free radical copolymerization reaction with other vinyl monomers was demonstrated in our previous study [11][12][13].…”

“…Acrylic monomers from olive and soybean oil were synthesized using one-step transesterification reaction of N-hydroxyethyl acrylamide with plant oil triglycerides in the presence of catalytic amounts of sodium hydroxide. The detailed synthesis procedure of POBM synthesis and its characterization are described in [11].…”

“…The unsaturation amount of latexes in monomer feed (UMF) was calculated using the approach described in [11].…”

“…Fragments of plant oil-based acrylic monomers (POBMs) recently synthesized in our group while being incorporated in macromolecules impacted thermomechanical properties of the resulting copolymers by decreasing their Tg [11,12]. This indicates that the presence of such constituents in the copolymer structure can provide internal plasticization effects, making the resulting materials more environmentally friendly compared to conventional products where low molecular phthalates are used.…”

“…The internal plasticization effect can be achieved by copolymerization of various commercial vinyl monomers with a library of POBMs developed in our group [11][12][13]. When long unsaturated fatty acid fragments (C18) of POBMs are incorporated into the macromolecules, they can reduce the intermolecular interactions and increase intermolecular distance, thus increasing chain mobility and facilitating polymer softening (plasticizing).…”