Abstract
Cyanoethylated amylopectins (CEAP) were synthesized with cyanoethylation of amylopectin (AP) using acrylonitrile in the presence of sodium hydroxide. The degree of cyanoethylation in CEAP was in the range from 0.80 to 2.41. Dielectric properties for AP and CEAP were measured at different frequencies and temperatures. Dielectric loss-frequency plots showed that the peaks of dielectric loss which were attributed to a side chain relaxation of cyanoethyl groups shifted to lower frequencies and higher temperature range as compared with those attributed to primary hydroxyl groups in AP. These side chain relaxations obeyed Cole-Cole's circular arc law and the Cole-Cole parameters, dielectric increment (εS-ε∞) and distribution parameter (β) were determined. The values of εS-ε∞ for CEAP were larger than those for AP and the distribution of relaxation time broadened with decreasing temperature. From the frequency-temperature locations of loss factor maximum, the activation free energy, enthalpy and entropy changes for the side chain relaxations were determined. The value of the activation free energy in CEAP suggested that the orientation of cyanoethyl groups were somewhat more restricted as compared with that of hydroxyl groups.
