Lewis Acid + Ligand Regulates α, β-unsaturated Ketone Radical Stereoregularity Polymerization

The stereoregularity of polymers often significantly affect the properties and functionsof the polymers. The radical polymerization is widely used in the polymer industry,because of its characteristics, the stereoregularity polymerization is very difficult. α,β-unsaturated ketone monomer is widely used for industrial and academic and therehas not been a research report on the stereoregularity radical polymerization of itspolymer. We synthesized menthyl vinyl ketone (MVK) in this paper. Polymers withdifferent microstructure were obtained by radical polymerization and thepolymerization conditions, which have some effect on the stereoregularity of PMVK,were examined. The key results of research work are listed below:1. Menthyl vinyl ketone (MVK) was synthesized by means of dehydrohalogenation ofβ-halo ketones.2. The obtained monomer was polymerized and the influence of polymerizationconditions on the yield and molecular weight of the polymers were examined. WhenMVK polymerized using trifluoromethanesulfonate as Lewis acid have a higher yieldand relatively low molecular weight. As the decrease of polar of the ligand, polymeryield decreased. Small polar solvent such as toluene is more conducive to thepolymerization proceeds and have a high yield. As the increases of temperature, theyield and Mnof the polymer decreased.3. We studied the stereoregularity of synthetic polymers. The stereoregularity of thepolymers was studied by13C NMR, polarimeter, UV and CD.The polymer got in thepresence of Lewis acid Yb(OTf)3and ligand H2O combination have the beststereoregularity.4. Effects of reaction conditions such as solvent and temperature, which haveinfluence on the stereoregularity of polymer were studied in this work. PMVKobtained by using weak polar solvent such as toluene have the higher stereoregularity,but have the lower stereoregularity by using the polar solvent such as CHCl3and THF.If we use the larger polar solvents CH3OH, the polymerization was not happened. Thepolymer tacticity becomes better as the polymerization temperature decreases. Thepolymer got at60℃has the highest optical activity and have the best stereoregularity.5. Summing up the above analysis can concluded that the polymerization in thepresence of Lewis acid Yb(OTf)3and ligand H2O combination by using toluene aspolymerization solvent at60℃have the best stereoregularity.6. To investigate the interaction between the Lewis acids, ligand and the monomer,1HNMR spectra of MVK in the absence, in the presence of various Lewis acids and H2Owere obtained in toluene-d8. Lewis acid Yb(OTf)3+ligand H2O combination have astronger interaction with monomer and have a better stereoregularity control and gotthe best stereoregularity polymer.