SYNTHESIS, CHARACTERIZATION, AND RING-OPENING POLYMERIZATION OF THE CYCLIC OLIGOMERS OF POLY(OXY-1,3-PHENYLENECARBONYL-1,4-PHENYLENE)

The cyclic oligomers (cyclomers) of the title composition were prepare d from 4-fluoro-3'-hydroxybenzophenone by nucleophilic aromatic substi tution. Cyclomers prepared in dimethyl sulfoxide and toluene at 150-16 0 degrees C using pseudo-high dilution contained a high fraction of cy clic dimer, which was isolated by vacuum sublimation. Cyclomers prepar ed in o-dichlorobenzene at 180 degrees C using catalytic 18-crown-6 we re suitable for polymerization. High-performance liquid chromatography was used to quantify the mixtures. The ring-opening polymerization of the cyclic dimer was studied using nucleophilic initiators. The conve rsions and relative molecular weight distributions were measured using gel permeation chromatography. Absolute molecular weights were estima ted on the basis of laser lightscattering measurements using cyclomer- free polymer samples. Cesium fluoride and alkali-metal carbonates gave incomplete conversion of the cyclic dimer to very high molecular weig ht polymers. Potassium and cesium 4-benzoylphenolate gave essentially complete conversion and their stoichiometry controlled the molecular w eights. The amorphous polymers possessed T-g = 132 degrees C and M-w = 60 0000-180 000. The initiators are differentiated by the competition between the chain extension of the linear species generated by initia tion and propagation of the ring-opening polymerization. The reactivit y of the cyclomers was correlated with their H-1 and C-13 NMR chemical shifts. The cyclic dimer is less reactive than the higher cyclomers d ue to its structure. X-ray crystallography showed that the p-phenylene rings of the cyclic dimer are partially rotated out of conjugation wi th the carbonyls due to steric interactions with the m-phenylene rings . The steric and electronic effects, and the chemistry of the cyclomer s in general, are due to the 3,4'-catenation of the repeat unit.