Thermal Reactions of Aromatic Diacetylenes: An Insight to Amorphous State Polymerization of Diacetylenes

Abstract

Several aromatic diacetylenes were heated in molten state, and the formation of diradicals was studied by ESR spectroscopy. Intense ESR signals were observed even at temperatures as high as 180°C. The formation of radical species at such low temperatures was explained by the formation of oligomeric species. The numbers of unpaired electrons in the molten state reached to 1021 electrons per mole of diacetylene, when heated to 180°C, and deep red materials were obtained. Surprisingly the radicals did not disappear when exposed to air showing that the radicals are stable in air. Keywords: aromatic diacetylenesdiradicalsESR spectraoligomerization Acknowledgments This work was supported by the DGAPA grant from our university with the contract number IN102401. Thanks are also due to Mr. Miguel A. Canseco for his assistance in thermal analysis. Notes a Time intervals between temperatures = 15 minutes. Heated in the cavity. b Approximate temperature at which the DSC curves started to rise. *Undetectable from ESR. #From DSC. Heating rate = 10°C/min under N2.