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A multiple aromatic ether linked phthalonitrile was synthesized and characterized. The oligomeric phthalonitrile monomer was prepared from the reaction of an excess amount of bisphenol A with 4,4′‐difluorobenzophenone in the presence of K2CO3 as the base in an N,N‐dimethylformamide/toluene solvent mixture, followed by end capping with 4‐nitrophthalonitrile in a two‐step, one‐pot reaction. The monomer properties were compared to those of the known resin 2,2‐bis[4‐(3,4‐dicyanophenoxy)phenyl]propane after being cured in the presence of bis[4‐(4‐aminophenoxy)phenyl]sulfone. Rheometric measurements and thermogravimetric analysis showed that the oligomeric phthalonitrile resin maintained good structural integrity upon heating to elevated temperatures and exhibited excellent thermal properties along with long‐term oxidative stability. The ether‐linked phthalonitrile resin absorbed less than 2.5% water by weight after exposure to an aqueous environment for extended periods. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4136–4143, 2005

An aromatic, diether‐linked phthalonitrile resin, prepared from 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl, exhibits excellent thermo‐oxidative properties. The resin is easily processed from the melt of the monomer in a controlled manner as a function of the amine curing agent and processing temperatures. Polymerization occurs by a cyclic addition reaction without the formation of volatile by‐products. The polymerization reaction can be stopped at a prepolymer stage. The prepolymer can be stored indefinitely at ambient conditions without further reaction. The modulus and viscoelastic properties of the resin were found to be a function of the postcuring conditions.

Phthalonitrile polymers offer promise as matrix materials for advanced composite applications. The phthalonitrile monomer is readily converted to a highly crosslinked thermosetting polymer in the presence of thermally stable organic amine catalysts. Rheometric studies were conducted to elucidate the optimum amine concentration for composite formulations. High quality composite panels were processed in an autoclave using unsized IM7 carbon fibers. Mechanical properties of the phthalonitrile/carbon composite are either better than or comparable to the state‐of‐the‐art PMR‐15 composites. Dynamic mechanical analysis reveal that samples postcured at elevated temperatures (375°C) do not exhibit a glass transition temperature up to 450°C and also retain °90% of their initial modulus at 450°C. Flame resistance of phthalonitrile/carbon composites, evaluated by cone calorimetric studies, excels over that of other polymeric composites for marine applications. The composites also show low water uptake, <1% after exposure to water for 16 months.

An improved synthetic method has been developed for oligomeric aromatic ether ketone‐based phthalonitrile (PN) resins. A new curing additive was studied that lowers the cure temperature of the PN resin to around 150 °C and compared to the traditional high‐temperature aromatic diamine. Mechanical and thermo‐oxidative analyses of polymeric samples from both systems were determined and compared under various curing conditions. The PN polymer exhibited low water absorption regardless of the chosen cure system. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1662–1668

Multiple aromatic ether-linked phthalonitrile polymers have been synthesized and characterized. The oligomeric monomers are prepared from reaction of an excess amount of a bisphenol such as 4,4'-(hexafluoroisopropy1idene)bisphenol or 4,4'-dihydroxybiphenyl with 4,4'-difluorobenzophenone in the presence of either weak or strong bases in N-methylpyrrolidinone (NMP) as solvent, followed by end-capping with 4-nitrophthalonitrile. The oligomeric phthalonitrile monomers were cured in the presence of a minute quantity of 1,3-bis(3-aminophenoxy)benzene or p-toluenesulfonic acid. The thermal and oxidative properties of two such polymeric systems were compared under identical curing conditions.

A series of low-melting phthalonitrile oligomers were prepared in which variable-length multiple aromatic ether linkages interconnect the terminal phthalonitrile units. These materials were designed to address the need for a processable resin system with good high-temperature properties. The melt-processable oligomers are obtained using a modified-Ullman ether reaction between a bisphenol and a dihalobenzene to form a hydroxyl-terminated oligomeric intermediate that is endcapped by reaction with 4-nitrophthalonitrile. Viscosity measurements show that the phthalonitrile oligomers are polymerized at a moderate temperature (200°C) using the typical aromatic diamine curing additives, bis[4-(4-aminophenoxy)phenyl]sulfone and 1,3-bis(3-aminophenoxy)benzene. The oligomeric phthalonitrile/diamine mixtures exhibit a low complex melt viscosity (0.01-0.1 Pa s) at 200°C. Differential scanning calorimetric analysis is used to follow the polymerization as the oligomeric phthalonitrile/diamine mixtures are heated to elevated temperatures. Thermal and dynamic mechanical properties of thermally-cured oligomeric phthalonitrile polymers are systematically evaluated and compared with those of two other high temperature thermosetting phthalonitrile polymers, 4,4~-bis(3,4-dicyanophenoxy)biphenyl and 1,3- bis(3,4-dicyanophenoxy)benzene. After thermal treatment at 425°C for 8 h, the oligomeric phthalonitrile polymers exhibit char yields of 70% when heated to 1000°C in flowing nitrogen and decomposition temperatures in excess of 500°C when heated in either flowing nitrogen or air. Rheometric measurements indicate that the fully cured oligomeric phthalonitrile polymers do not soften or exhibit a glass transition temperature upon heating to 450°C. Overall, studies on the phthalonitrile oligomers and the corresponding polymers reveal an attractive combination of processability, thermal and thermo-oxidative stability and good dynamic mechanical properties for these materials

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