Synthesis and properties of novel soluble polyamides having ether linkages and laterally attached p-terphenyl units

A new ether-bridged aromatic dicarboxylic acid, 2',5'-bis(4-carboxyphenoxy)-p-terphenyl (3), was synthesized by the aromatic fluoro-displacement reaction of p-fluorobenzonitrile with 2',5'-dihydroxy-p-terphenyl in the presence of potassium carbonate, followed by alkaline hydrolysis. A set of new aromatic polyamides containing ether and laterally attached p-terphenyl units was synthesized by the direct phosphorylation polycondensation of diacid 3 with various aromatic diamines. The polymers were produced with high yields and moderately high inherent viscosities (0.44-0.79 dL/g). The polyamides derived from 3 and rigid diamines, such as p-phenylenediamine and benzidine, and a structurally analogous diamine, 2',5'-bis(4-aminophenoxy)-p-terphenyl, were semicrystalline and insoluble in organic solvents. The other polyamides were amorphous and organosoluble and could afford flexible and tough films via solution casting. These films exhibited good mechanical properties, with tensile strengths of 91-108 MPa, elongations to break of 6-17%, and initial moduli of 1.95-2.43 GPa. These polyamides showed glass-transition temperatures between 193 and 252 degreesC. Most of the polymers did not show significant weight loss before 450 degreesC, as revealed by thermogravimetric analysis in nitrogen or in air. (C) 2004 Wiley Periodicals, Inc.