Catalytic effects of sodium salts with varied anionic pairs on the polymerization of liquid crystal polyesters.

Liquid crystal polyesters (LCPs) have attracted growing attention due to the increasing demand for military equipment and 5G communication devices. Commonly, the LCPs are polymerized by transesterification reaction catalyzed through inorganic salts, however, the effects of anionic pairs of catalysts on the LCP polymerization have not been studied carefully. Herein, five kinds of sodium salts with varied anionic pairs as catalysts to facilitate LCP polymerization are investigated for the first time. The catalytic activity is analyzed by the evolution of the liquid crystal (LC) phase during polymerization based on the thin-film polymerization technique. The temperature from 190 °C to 270 °C and the catalyst content in the range from 0 to 0.1 wt% are compared, demonstrating that temperature at 270 °C and catalyst content at 0.1 wt% are the best polymerization conditions for all sodium salts. It is found that sodium formate has the best catalytic activity for the polymerization of LCP in all experimental conditions, in comparison with sodium acetate, sodium propionate, sodium butyrate, and sodium p-hydroxybenzoate. The successful polymerization is also determined by FT-IR spectra, performing the declined intensity of vibration peak at 1370 cm−1 ascribed to the vanishment of acetoxy groups as well as the enhanced intensity of vibration peak at 1735 cm−1 ascribed to the formation of ester groups. [ABSTRACT FROM AUTHOR]