Synthesis and properties of polyamide–imides containing fluorenyl cardo structure

A series of alternating polyamide–imides (PAIs) with fluorenyl cardo having inherent viscosities of 0.38–0.88 dL/g was synthesized by one‐pot polycondensation of cardo diamines, trimellitic anhydride, and various aromatic diamines including p ‐phenylene diamine, m ‐phenylene diamine, 4,4'‐oxydianiline, 3,4'‐oxydianiline, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane, 2,2‐bis[4‐(3‐amino phenoxy)phenyl]propane using triphenyl phosphite as condensing agents. Most of the polymers were readily soluble in a variety of organic solvents, such as N ‐methyl‐2‐pyrrolidin‐one, N,N ‐dimethylacetamide (DMAc), N,N ‐dimethylformamide, dimethyl sulfoxide, pyridine, and tetrahydrofuran, etc. PAIs exhibited better solubility when alkyl substituents were incorporated. Moreover, the effects of the linkage of imide/amide on the properties of PAIs were also discussed. The glass‐transition temperatures of these polymers were recorded between 235 and 448°C by DSC and 10% weight loss temperature of all polymers exceed 450°C in air. The films of the resulting PAIs could be cast from their DMAc solutions. These films had a tensile strength in the range of 43‐111 MPa, and an elongation at break in the range of 1.5–7.1%.