EPR study of liquid-crystalline vectra copolyester

EPR signals from the samples of thermotropic liquid-crystalline (LC) Vectra copolyester were observed and analyzed. It is shown that parameters of the EPR signal provide information on the sample prehistory: the signal amplit ude depends on the intensity of thermooxidative degradation, while the line width is determined by the character of molecular packing in the LG regions . It is established that the regions of unpaired electron delocalization in crease as a result of mesophase densification upon the polymer annealing in the vicinity of the melting temperature. The results of calculation of the rate and activation energy of the reaction of free radical formation in th e copolyester are presented and compared with analogous parameters for PET.