Synthesis and Properties of Novel Aromatic Copolyamides Containing Phthalazinone Moiety

A series of novel aromatic copolyamides were synthesized by the direct polycondensation of 2‐(4‐carboxyphenyl)‐4‐[4‐(4‐carboxyphenoxyl)phenyl]‐phthalazinone (1), terephthalic acid (TPA), and four commercial diamines. The inherent viscosities of the polyamides were between 0.79～1.56 dL/g. Introduction of the non‐coplanar phthalazinone segments into the main chains remarkably decreased the crystallinity and improved the solubility of the copolyamides. When the percentage of 1 in the diacid monomers was above 50%, the copolymers were soluble in aprotic polar solvents, such as N‐methyl‐pyrrolidinone and N,N‐dimethylacetamide. The copolyamides showed high thermal properties associated with the glass transition temperatures in the range of 276～337°C and 10% wt loss temperatures in nitrogen over 496°C. Some polymer films cast from NMP solution had tensile strengths up to 123.4 MPa, initial moduli up to 2.10 GPa, and elongation at break values up to 9.6%.