Poly(aryl ether-benzoxazoles)

Abstract

A general method for the preparation of poly(aryl ether-benzoxazoles) has been developed where the generation of an ether linkage is the polymer-forming reaction. We found that aryl fluorides para to a 2-benzoxazolyl group were activated toward nucleophilic aromatic substitution with phenoxides. Facile displacement occurred at this position since the benzoxazole ring can stabilize the negative charge developed in the transition state through a Meisenheimer complex, analogous to conventional activating groups (e.g. sulfone or carbonyl). Appropriately substituted dihalo bisbenzoxazoles, 2,2'-bis[2-(4fluorophenyl)benzoxazol-6-yl]hexafluoropropane, 2,2'-bis(4-fluorophenyl)-6,6'-bibenzoxazole, and 2,2'-(4fluorophenyl)-5,5'-bibenzoxazole, were prepared and polymerized with bisphenols in N-methyl-2-pyrrolidone in the presence of K2C03. High molecular weight polymers were obtained, with glass transition temperatures ranging from 213 to 300 °C. The resulting polymers were processable from solution or the melt and showed excellent thermal stability and mechanical properties. This synthetic route affords the poly-(benzoxazole) analogue of poly(ether-imide) and shows many of the same desirable characteristics.

Synthesis and Characterization of Highly Soluble Poly(aryl ether ketone‐benzoxazole) Copolymers with Hexafluoroisopropylidene Moieties by Direct Copolymerization

“…In previous research, Hilborn et al demonstrated oxazole-activated fluoro-displacement as a route to synthesize PBO with aryl ether linkages. [12] The resulting poly(ether benzoxazole) was soluble in NMP even at high solid concentration (15-25 wt.-%). This one step method has been extended here to synthesize processable poly(aryl ether ketonebenzoxazole) (PAEKBO) copolymers with benzoxazolecontaining and ether-ketone-containing segments in the polymer main chains.…”

“…the distillation of CHP under a vacuum. [12] The long reaction time and high temperature conditions made the reaction procedure complicated. PPA is a relatively common solvent for preparing heterocyclic compounds by a condensation method and the reactions readily proceed at %200 8C.…”

Synthesis and thermal properties of thermosetting bis-benzocyclobutene-terminated arylene ether monomers

“…4,4Ј-difluorobenzophenone and 4,4Ј-difluorodiphenylsulfone were commercially available compounds. Although 2,2-bis[2-(4-fluorophenyl)benzoxazol-6-yl]hexafluoropropane had been prepared from the condensation reaction of 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane and 4-fluorobenzoic acid, 18 we found that shorter reaction time (12 h vs. 2-4 days) and lower cyclodehydration temperature (180°vs. 260°C) were needed in the presence of trimethylsilyl polyphosphate.…”

Synthesis and characterization of novel poly(arylene ether)s containing 1,3,4-oxadiazole units

“…The electronic effect of an oxadiazole heterocycle on the 2-phenyl group can be evaluated by 1 H NMR, as the deshielding of the proton ortho to a substituent is indicative of an electron-withdrawing group 27,32,33) . The 1 H NMR spectral assignments for monomers 4 a -4 c showed the ortho protons of the 2-phenyl ring (H mers 4 a -4 c and p-cresol were carried out in an NMP or DMAc/toluene solvent mixture in the presence of K 2 CO 3 (Scheme 1).…”