抄録
We have reported the thermal properties of the side-chain type liquid-crystalline polyacrylates introduced a siloxane bond to the spacer part. In this paper, the dynamic behaviors of P-1 〜 P-7, as shown in table, were investigated by dielectric relaxation spectroscopy over the frequency range 10 〜 106 Hz at different temperatures (above room temperature). For all samples, the dielectric loss peak arising from δ-relaxation process was detected. As a result of the fitting by Fuoss-Kirkwood function, distribution parameter, β, of the siloxane-spacer type, SS, was larger than that of the alkylene-spacer type, AS, at the same reduced temperature,T_red (=T/Tg). By using the critical frequencies, fm, of each polymer at various temperatures, 1n fm-1/T and 1n fm-1/Tred were plotted. The dielectric relaxation time, τδ(=1/2πf_m), of SS was longer than that of AS at the same Tred. Since the introduction of siloxane linkage into a spacer chain decreases the Tg of a polymer, the viscosity would relatively increase at the same Tred. On the contrary,τδ of SS was very shorter than that of AS at the same absolute temperature. The values of the apparent activation energy of SS and AS were estimated as about 80 kJ-mol-1 and about 100 kJ-mol-1, respectively. Therefore, it is suggested that a siloxane-spacer unambiguously enhances the mobility of side-chain by decreasing Tg.
