NOVEL WHOLLY AROMATIC POLYAMIDE-HYDRAZIDES .4. EFFECT OF POLYMERS STRUCTURAL COMPOSITIONS ON THEIR PROPERTIES

The effect of structural differences on the physical, thermal and mech anical properties of a series of wholly aromatic polyamide-hydrazides containing different p-/m-phenylene moieties has been investigated. Fi ve novel polymers were synthesized by a low temperature solution polyc ondensation reaction of p-aminosalicylic acid hydrazide [PASH] with ei ther terephthaloyl chloride [TC1], isophthaloyl chloride [IC1] or mixt ures of various combinations of TC1 and IC1 in anhydrous N,N-dimethyla cetamide [DMAc]. The prepared polymers possess from 50/50 to 100/0 mol .% p-/m-oriented phenylene rings. Polymers structures were identified by elemental analysis and IR spectrophotometry. All the polymers have the same structural formula except the way of linking phenylene units inside the polymer chain. They were readily soluble in several organic polar solvents such as DMAc, N,N-dimethylformamide [DMF], dimethyl su lphoxide [DMSO], N-methyl-2-pyrrolidone [NMP] and hexamethyl phosphora mide [HMPA] and could be cast into flexible films. Their solubilities were found to be enhanced remarkably with introduction of m-phenylene nuclei into the polymers. Their intrinsic viscosities were ranged from 4.7 to 1.09 dl g(-1) in DMAc at 30 degrees C and increased with the i ncrease of p-phenylene units content. Thermal gravimetric studies reve aled that the perfectly p-oriented type of polymer has better thermal stability relative to that of the other polymers. Further, mechanical properties of the films produced from these polymers are improved mark edly by substitution of p-phenylene units for m-phenylene units. All t hese polymers were found to be amorphous as confirmed by X-ray diffrac tion.