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

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) methacryla te (TCDM), starting from the reaction of glycerol and cyclohexanecarbaldehy de, is reported. The process involved the preparation of different alcohol acetals and esterification with methacryloyl chloride of the corresponding cis and trans 5-hydroxy compounds of 2-cyclohexyl-1,3-dioxane. The radical polymerization reactions of both monomers, under the same conditions of tem perature, solvent, monomer, and initiator concentrations, were studied to i nvestigate the influence of the monomer configuration on the values of the propagation and termination rate constants (k(p) and k(t)). The values of t he ratio k(p)/k(t)(1/2) were determined by UV spectroscopy by the measureme nt of the changes of absorbance with time at several wavelengths in the ran ge 275-285 nm, where an appropriate change in absorbance was observed. Reli able values of the kinetics constants were determined by UV spectroscopy, s howing a very good reproducibility of the kinetic experiments. The values o f k(p)/k(t)(1/2), in the temperature interval 45-65 degrees C, lay in the r ange 0.40-0.50 L-1/2/mol(1/2)s(1/2) and 0.20-0.30 L-1/2/mol(1/2)s(1/2) for CCDM and TCDM, respectively. Measurements of both the radical concentration s and the absolute rate constants k(p) and k(t) were also carried out with electron paramagnetic resonance techniques. The values of k(p) at 60 degree s C were nearly identical for both the trans and cis monomers, but the term ination rate constant of the trans monomer was about three times that of th e cis monomer at the same temperature. (C) 2000 John Wiley & Sons, Inc.