Broad-Band Dielectric Spectrocopy of Polymer Chains Containing Structurally Complex Side Groups

The temperature dependence of the α and β relaxations of poly(2-phenyl-5-acryloxymethyl-5-ethyl-1,3-dioxacyclohexane) is studied by broad-band dielectric spectroscopy. The strength of the α relaxation decreases with increasing temperature, pointing to an onset temperature (Δε<INF>α</INF> = 0) of ca. 97 °C. Seen from the high-temperature side, the α relaxation starts with zero intensity at the onset temperature and steeply increases with decreasing temperature until it levels off in the vicinity of T<INF>g</INF>. Whereas in the glassy state the strength of the β relaxation is only slightly dependent on temperature, it undergoes a strong increase at temperatures above T<INF>g</INF>. Arrhenius plots of both relaxations show that the β process remains operative at temperatures above the onset temperature of the α relaxation. The temperature dependence of the stretch exponent does not show a definite trend, most of the values obtained lying in the interval 0.3−0.5.