Influence of the stereochemical configuration on the radical polymerization of methacrylic monomers: cis- and trans-(2-cyclohexyl-1,3-dioxan-5-yl) methacrylates

Abstract

ABSTRACT: The synthesis of two new isomeric monomers, cis-(2-cyclohexyl-1,3-dioxan- 5-yl) methacrylate (CCDM) and trans-(2-cyclohexyl-1,3-dioxan-5-yl) methacrylate (TCDM), starting from the reaction of glycerol and cyclohexanecarbaldehyde, is re- ported. The process involved the preparation of different alcohol acetals and esterifi- cation with methacryloyl chloride of the corresponding cis and trans 5-hydroxy com- pounds of 2-cyclohexyl-1,3-dioxane. The radical polymerization reactions of both mono- mers, under the same conditions of temperature, solvent, monomer, and initiator concentrations, were studied to investigate the influence of the monomer configuration on the values of the propagation and termination rate constants (kp and kt).The values of the ratio kp/kt 1/2 were determined by UV spectroscopy by the measurement of the changes of absorbance with time at several wavelengths in the range 275–285 nm, where an appropriate change in absorbance was observed. Reliable values of the kinetics constants were determined by UV spectroscopy, showing a very good repro- ducibility of the kinetic experiments. The values of kp/kt 1/2, in the temperature interval 45– 65 °C, lay in the range 0.40 – 0.50 L1/2/mol1/2s1/2 and 0.20 – 0.30 L1/2/mol1/2s1/2 for CCDM and TCDM, respectively. Measurements of both the radical concentrations and the absolute rate constants kp and kt were also carried out with electron paramagnetic resonance techniques. The values of kp at 60 °C were nearly identical for both the trans and cis monomers, but the termination rate constant of the trans monomer was about three times that of the cis monomer at the same temperature.