Synthesis and characterization of poly(organophosphazenes) bearing Schiff's base linkages

Summary

Two new classes of Schiff's base poly(organophosphazene)s have been synthesized and characterized. The substitution degree of the Schiff's base linkage was found for the products of the form, [NP(O-Ph-CHO)_x(O-Ph-CH=N-Ph-R)_y]_n(polymer II series), where R are H, OCH₃, OH(p), OH(m) and -N=N-Ph, was less than 35%, while the products of the second class, [NP(OCH₂CH₂OCH₂CH₂O-Ph-CHO)_x(OCH₂CH₂OCH₂-CH₂O-Ph-CH=N-Ph-R)_y]_n (polymer III series), where R are H, COOH(m), COOH(p), NO₂, and OCH₃, marked 65% on the average. The solubility of the polymers in the common organic solvents was found very poor, except such strong polar or aprotic solvents at elevated temperature. The existence of flexible spacer group connected to the Schiff's base linkage has greatly influenced the thermal properties of the polymers. DSC measurements revealed about 100°C of melting transition for the polymer II series, while 214°C for the polymer III series with exhibiting multistage of thermal transition. The DSC results gave some evidences that the products of polymer III series have potentials for the thermotropic liquid crystalline polymers.