Radical polymerization of isomeric methacrylic monomers: cis- and trans-(2-phenyl-1,3-dioxan-5-yl) methacrylate

Abstract

Two new monomers, cis-(2-phenyl-1,3-dioxan-5-yl) methacrylate (CPDM) and trans-(2- phenyl-1,3-dioxan-5-yl) methacrylate (TPDM), have been synthesized. The stereochemical configuration in both monomers was unequivocally assigned by correlation 1H-13C NMR experiments. The radical polymerization reactions of both monomers were studied by ultraviolet spectroscopy and electron paramagnetic resonance spectroscopy to determine the polymerization rate parameter kp/kt1/2 and the absolute propagation and termination rate constants (kp and kt) at different temperatures. The values of kp/kt1/2 lie in the range 0.40-0.55 L1/2/(mol1/2 s1/2) for CPDM and 0.29-0.37 L1/2/(mol1/2 s1/2) for TPDM at temperatures between 45 and 70 °C, showing that the polymerization rate of the cis monomer with the substituents in equatorial-axial positions on the dioxane ring is higher than that of its trans counterpart with the phenyl and ester residue in equatorial positions on the dioxane ring. Using EPR measurements of the polymer radical concentrations, similar values for kp were obtained for both trans and cis monomers, whereas the termination rate constant of the trans monomer was about twice that of the cis monomer at the same temperature.