Synthesis And Properties Of Novel Aromatic Polyamides Containing Phthalazinone Moieties

Aromatic polyamides are a class of high-performance polymers and they are widely used in various fields due to their high thermal stability and good mechanical properties. However, high rigidity of the backbone and strong hydrogen bonding interchains result in their insolubility in most organic solvents and also give rise to their high softening temperatures. These properties make them generally difficult and expensive to process. For example, Kevlar?, which structure is poly(p-phenylene terephthalamide), can only be spinned from its conc. H₂SO₄ solution. In order to improve the solubility while maintaining the excellent properties, phthalazinone moieties and ether linkages were introduced into the polymer main chain. Thus novel fiber could be spinned directly from their polymer solutions.Three series of novel aromatic copolyamides PA I III were synthesized from three different phthalazinone-containing diacids, terephthalic acid and some commercial diamines by Yamazaki polycondensation method. Their structures were characterized by FT IR and ¹H NMR. The effect of the ratios of phthalazinone moieties and the structure of diamines on the polymers' morphology, solubility and thermal properties was systemicly studied. Some films of the polyamides were obtained by casting from their NMP solutions and showed good mechanical properties.The copolyamides P1 were prepared from l,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)]phthalazin-l-one (DHPZ-DA), p-phenylenediamine (PPD) and terephthaloyl dichloride (TPC) by low temperature solution polycondensation method. The polymers had middle inherent viscosities of 1.21-3.57 dL/g. The introduction of phthalazinone moieties and ether linkages into the main chain improved their solubility in some polar aprotic solvents. The glass transition temperatures (7_gs) were all above 310℃ and the 10% weight loss temperatures were higher than 500°C. WAXD measures indicated that these polyamides were amorphous. Most of these polyamides formed anisotropic phase in their conc. H₂SO₄, NMP (lwt% LiCl) and DMAc (lwt% LiCl) solutions. In addition, some difference in the inherent viscosity, T_g, solubility and critical concentration (C*) values were observed by changing adding manner of the monomers.The copolyamides P2 were prepared from DHPZ-DA, PPD, 4,4'-diaminodiphenylether and TPC. With some well designed experiments, all the factors which may affect the polycondensation, including reaction temperature, monomer concentration, acid receptor concentration, salt concentration and so on, were tested, and the optimized factors were found.