Macrocycles 32. Syntheses of Cyclic Poly(Ether Ketone)s of Bisphenol-A

Abstract

Two classes of poly(ether ketone)s were prepared from bisphenol-A, namely by polycondensation with 4, 4′-difluorobenzophenone or with 2,6-difluorobenzophenone and 4′-tert.butyl-2,6-difluorobenzophenone. Two different synthetic methods were compared. First, polycondensations of the free bisphenol-A in DMSO or sulfolane with azeotropic distillation of water. Second, polycondensations of bistrimethylsilyl bisphenol-A in N-methylpyrrolidone. The second approach gave higher yields and higher molecular weights ( Mnvalues up to 85000 Da and Mwvalues up to 190000 Da). The matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra revealed that the fraction of cyclic oligomers and polymers systematically increased with higher molecular weights. A few polycondensations of silylated 4-tert.butylcatechol with 4, 4′-difluorobenzophenone confirmed the trends observed for silylated bisphenol-A. Under optimum conditions cyclic poly(ether ketone)s were detectable in the MALDI-TOF mass spectra up to molecular weights of 18 000 Da.