Direct Observation of α‐Chloro‐p‐quinodimethane as the Real Monomer in the Gilch Polymerization Leading to Poly(p‐phenylene vinylene)s

Abstract

AbstractIt is the general consensus that in Gilch polymerizations the 1,4‐bis(chloromethylene)benzene starting material first changes into p‐quinodimethane intermediates which then act as the real monomers. However, direct observation of these intermediates has not been possible so far. This is because usually the p‐quinodimethane auto‐initiates its rapid radical polymerization instantaneously, keeping its concentration extremely low throughout the whole process. Here it is shown that, when the reaction is carried out at very low temperatures, the formation of p‐quinodimethane still proceeds but chain growth is suppressed. Hence, the concentration of the active monomer reaches a level sufficient for NMR analysis.magnified image