Polyphenylenes via Bis(2-pyrones) and Diethynylbenzenes. The Effect of m- and p-Phenylene Units in the Chain

Abstract

Polyphenylenes via Bis(2-pyrones) 343 mmol) of freshly distilled phenylacetylene in 2.1 mL of 1,2,4-trichlorobenzene was placed in a 10-mL glass ampule. The solution was degassed by two successive freeze (liquid nitrogen)-evacuate-thaw cycles. The ampule was sealed and placed in a 500-mL Paar bomb containing 7 5 mL of 1,2,4-trichlorobenzene in order to partially equalize the pressure inside and outside the ampule. The bomb was heated to 210 "C for 69 h. The bomb was cooled and the ampule was opened. Gas chromatography of the solution (240 "C, 5 f t X 0.375 in., 15% SE-30 on Chromosorb P) gave overlapping peaks of m-and pterphenyls. Comparison of the peak shape with standard solutions of authentic samples indicated the ratio of meta to para was 2:l. The yield as determined by comparison with standard solutions by gas chromatography was 68.5%. The infrared spectrum of the sample collected by preparative gas chromatography indicated the presence of both m -and p-terphenyls.Acknowledgment. T h e authors would like to thank Mr. R. Malins for his assistance with the M O calculations.ABSTRACT: Polyphenylenes with varying degrees of meta and para catenation have been synthesized utilizing the Diels-Alder 4 t 2 cycloaddition reaction of bis(2-pyrone) monomers with diethynylbenzenes. The polyphenylenes are yellow to brown, insoluble, highly crystalline, and thermally stable. Increasing amounts of meta catenation lower the T , and improve solubility.

Copolymerization of a bisanthracene compound with bismaleimides by Diels–Alder cycloaddition

“…The polymerization products are oligomers and their relatively low molecular weights are probably due to the steric effects and reversibility of the Diels–Alder reaction. In fact, the only instances where Diels–Alder polymerizations have yielded high molecular weight polymers are in the cases where the reactions are made irreversible via subsequent elimination of a small molecule 20. 21…”