Na. Mohamed, NOVEL WHOLLY AROMATIC POLYAMIDE-HYDRAZIDES .4. EFFECT OF POLYMERS STRUCTURAL COMPOSITIONS ON THEIR PROPERTIES, European Polymer Journal, 31(9), 1995, pp. 859-865
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.