Polyamides based on diamines containing aryloxy groups: Structure-property relationships

Aromatic polyamides containing different numbers of p-oxyphenylene groups and different catenated positions in the benzene rings were prepared from terephthalic acid (TPA) and isophthalic acid (IPA) with various aryloxy-containing diamines by means of the phosphorylation polycondensation reaction. Most of the polyamides were moderately to highly crystalline, as indicated by X-ray diffraction and DSC measurements. Polyisophthalamides were readily soluble in polar amide-type solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Some non-crystalline polyamides could afford tough films by solution casting. Most polyisophthalamides revealed discernible glass transition on their DSC curves, and their T_g values were recorded in the range of 215–238 °C. No discernible glass transitions were observed for the polyamides of TPA by DSC. The thermal stability of these polymers did not show clear dependence on the structure of the diacid or the diamine. In addition, a series of polyamides having pendant groups was synthesized from the polycondensation of TPA and IPA with 1,4-bis(4-aminophenoxy)benzene and its derivatives with methyl, tert-butyl, or phenyl substituent on the central benzene ring. In most cases, the incorporation of pendant groups generally resulted in an enhanced solubility and a decreased T_g and crystallinity.