A new series of high-performance poly(arylene phosphine oxide) (PAPO) materials were synthesized postpolymerization from fluorinated poly(arylene phosphine oxide) (f-PAPO). The new materials had increased solubility and film-forming ability over the parent f-PAPO. With the careful choice of the nucleophile, the thermal stability was also increased. The parent polymer f-PAPO was synthesized via Ni(0) coupling from aromatic chloride and mesylate monomers. Both monomers were polymerized successfully to create polymers with intrinsic viscosities of 0.235 and 0.123 dL/g, respectively. The higher molecular weight f-PAPO gave a glass transition of 320 degreesC and a char yield of 54% at 650 degreesC in air. The substitution of f-PAPO via nucleophilic aromatic substitution produced PAPO thermoplastics with significant changes in the properties. The largest increase in the thermal stability relative to f-PAPO was from 563 to 600 degreesC 10% weight-loss values in nitrogen after the displacement of fluoride by 4-aminophenol, which yielded poly[4-(4-aminopheonxyphenyl)bis(4'-phenyl)phosphine oxide]. Additionally, the char yield increased from 54 to 71% in air at 650 degreesC. The solubility of the parent polymer was improved after substitution with 3-tert-butylphenol, n-nonylamine, and poly(ethylene glycol)monomethyl ether. All of these became soluble in chloroform, N,N-dimethylacetamide, and dimethyl sulfoxide. Copolymers were syntliesized with 2,5-dichloro-4'-fluorobenzophenone to improve the solubility of f-PAPO without the loss of thermal stability. These copolymers also underwent nucleophilic aromatic substitution to create an epoxy cure agent that was used with the DEN 431 resin. (C) 2003 Wiley Periodicals, Inc.