Synthesis of polyphenylquinoxaline copolymers via aromatic nucleophilic substitution reactions of an A-B quinoxaline monomer

A self-polymerizable quinoxaline monomer (A-B) has been synthesized and polymerized via aromatic nucleophilic substitution reactions. An isomeric mixture of self-polymerizable quinoxaline monomers-2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline and 3-(4-hydroxyphenyl)-2-phenyl-6-fluoroquin polymerized in N-methyl-2-pyrrolidinone (NMP) to afford high molecular weight polyphenylquinoxaline (PPQ) with intrinsic viscosities up to 1.91 dL/g and a glass-transition temperature (T-g) of 251 degreesC. A series of comonomers was polymerized with A-B to form PPQ/polysulfone (PS), PPQ/polyetherether ketone (PEEK), and PPQ/polyethersulfone (PES) copolymers. The copolymers readily obtained high intrinsic viscosities when fluorine was displaced in NMP under reflux. However, single-electron transfer (SET) side reactions, which limit molecular weight, played a more dominant role when chlorine was displaced instead of fluorine. SET side reactions were minimized in the synthesis of PPQ/PS copolymers through mild polymerization conditions in NMP for longer polymerization times. Thus, the T-g's of PES (T-g = 220 degreesC), PEEK (T-g = 145 degreesC), and PS (T-g = 195 degreesC) were raised through the incorporation of quinoxaline units into the polymer. Copolymers with high intrinsic viscosities resulted in all cases, except in the case Df PPQ/PEEK copolymers when 4,4 ' -dichlorobenzophenone was the comonomer. (C) 2001 John Wiley & Sons, Inc.