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 C M (ratio of chain transfer and propagation rate constants) depends on monomer structure as follows: C M(LSM) > C M(SBM) > C M(SFM) > C 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 [T g = 4.2 °C for poly(SFM), T 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.
A one-step method that converts soybean oil into (acryloylamino)ethyl soyate, a new vinyl monomer of free radical polymerization, was developed. The synthesized monomer combines vinyl double bond (acryloyl functional group) and non-conjugated (isolated) double bonds of fatty acids. The double bond of the acryloyl group is reactive in a free radical chain polymerization that yields linear macromolecules containing isolated double bonds in side chains. Monomer reactivity ratios (r 1 , r 2 ) in copolymerization of the new soybean oil-based acrylic monomer (SBA) with styrene, methyl methacrylate, and vinyl acetate, as well as the Q-e parameters of the SBA, were determined. The obtained results indicate that copolymerization can be described with the classical Mayo-Lewis equation. In terms of polymerizability, the SBA can be classified as an acrylic monomer. The double bonds of the fatty acid chains remain mainly unaffected during the free radical polymerization. The remaining unsaturated fragments in the side chains make the resulting macromolecules capable of further oxidative cross-linking and the development of cross-linked polymer coatings.
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.
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