Synthesis and characterization of new diphenylfluorene-based aromatic polyamides derived from 9,9-bis[4-(4-carboxy-phenoxy)phenyl]fluorene

Abstract

A new bis(ether-carboxylic acid), 9,9-bis[4-(4-carboxyphenoxy)phenyl]fluorene (3), was synthesized from the nucleophilic fluorodisplacement of p-fluorobenzonitrile with the dipotassium bisphenolate of 9,9-bis(4-hydroxyphenyl)fluorene, followed by alkaline hydrolysis of the intermediate bis(ether nitrile). A novel series of aromatic polyamides containing ether and bulky fluorenylidene groups were prepared by the direct polycondensation of the diacid 3 with various aromatic diamines in N-methyl-2-pyrrolidone (NMP) solution containing dissolved CaCl2 using triphenyl phosphite and pyridine as condensing agents. The obtained polyamides have inherent viscosities in the range of 0.50–1.75 dL/g. All the polymers are readily soluble in a variety of organic solvents, such as NMP, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and m-cresol, and afford transparent, flexible, and tough films by solvent casting. These polyamides have glass transition temperatures ranging from 200 to 303°C and show no significant weight loss up to 450°C, with 10% weight loss being recorded above 511°C in nitrogen or air.