Relaxation response of polymers containing highly flexible side groups monitored by broadband dielectric spectroscopy

The relaxation behavior of poly(5-acryloxymethyl-5-methyl-1,3-dioxacyclohexane), a polymer containing highly flexible side groups, is studied by broadband dielectric spectroscopy in the frequency and temperature ranges 10(-1)-10(9) Hz and 123-473 K, respectively. Above the glass transition temperature T-g the dielectric loss in the frequency domain exhibits a prominent alpha absorption, followed in increasing order of frequencies by two secondary absorptions called 8 and gamma. At temperatures slightly higher than T-g, the alpha relaxation is well separated from the beta, but as temperature increases overlapping between both relaxations augments forming an alpha beta absorption in the vicinity of 420 K. This latter absorption displays a shoulder on its high-frequency side corresponding to the gamma relaxation. The strength of the alpha relaxation decreases with increasing temperature, eventually vanishing at the temperature at which the alpha beta absorption is formed. The time retardation spectra of the isotherms are calculated and further used to facilitate the deconvolution of the overlapping relaxations. The fact that the temperature dependence of the beta relaxation also describes that of the alpha beta absorption suggests that both relaxations have the same nature. It seems that as temperature increases, the alpha relaxation feeds on the beta absorption until its complete disappearance. The gamma relaxation, in turn, seems to increase at the expense of the alpha beta process at high temperature. (c) 2005 American Institute of Physics.