The synthesis and radical polymerization of 1,3-dioxan-5-yl-acrylate and 1,3-dioxan-5-yl-methacrylate are described. The mechanical and dielectric relaxation spectra of poly(1,3-dioxan-5-yl-acrylate) and poly(1,3-dioxan-5-yl-methacrylate) exhibit prominent subglass absorptions, the locations of which are not affected by the rigidity of the main chain. The subglass relaxations of poly(1,3-dioxan-5-yl-acrylate) and poly(1,3-dioxan-5-yl-methacrylate) are shifted nearly 20 degrees C toward lower temperatures with respect to those of poly(cyclohexyl acrylate) and poly(cyclohexyl methacrylate). The locations of the mechanical glass-rubber relaxations are not affected by the different nature of the rings located in the side groups. A study of the conductive contributions to the dielectric glass-rubber relaxation of poly(1,3-dioxan-5-yl-acrylate) and poly(1,3-dioxan-5-yl-methacrylate) is carried out using a theory that assumes that the dispersion displayed by the loss tan delta at high temperatures, in the frequency domain, arises from the Maxwell-Wagner-Sillars effect combined with Nernst-Planck electrodynamic effects caused by interfacial polarizations in the polymer-electrodes interface.