5-Ethyl-1,3-dioxane-5-yl)methyl acrylate (HEDA) and (5-ethyl-1,3-dioxane-5-yl)methyl methacrylate (HEDMA) were synthesized by reaction between acryloyl and methacryloyl chloride with 5-ethyl, 5-hydroxymethyl, 1,3-dioxane. The kinetics of the polymerization of both are studied at different temperatures in benzene solution. Dilatometric techniques and nonlinear least-squares methods were used to obtain the kinetic data and to determine the kinetic constants, respectively. The values of k p /k 1/2 t for the acrylic and methacrylic monomers are higher than those corresponding to methyl acrylate and methyl methacrylate, respectively. Important changes in k p /k 1/2 t with temperature occur in the polymerization of HEDA, and the corresponding Arrhenius plot gives an activation energy of 5.6 kcal mol 01 . On the contrary, only slight changes with temperature are observed in this ratio for HEDMA and the activation energy associated with the polymerization reaction is ca. 1.7 kcal mol 01 . The stereostructure of both polymers was determined by 13 C-NMR spectroscopy and the molar fractions of tactic dyads, triads (and in the case of the methacrylic polymer also pentads) were determined from different resonance signals. Finally, the glass transition temperatures of both PHEDA and PHEDMA are 33 and 123ЊC, respectively.