Synthesis of poly(phenyleneethynylene) without diine defects

Poly(phenyleneethynylene)s prepared by Pd/Cu-catalyzed synthesis contain diine defect structures. Diines are formed by reaction of Pd(II) species with ethynylides. The side reaction can be avoided by a low stationary state concentration of ethynylides. This can be achieved by a one pot reaction where removing of the trimethylsilyl groups and the polycondensation is simultaneously carried out. Deprotection is becoming the rate determining step, and thus the stationary state concentration of ethynyl compounds is low. A Cufree Pd catalyst is used. The absence of diines is shown in model reactions. An ester-containing poly(phenyleneethynylene) is prepared using the new technique. The polymer is amorphous, thermotropic, and lyotropic with a Tg of 41°C. It can be hydrolyzed to a polyelectrolyte with a rigid polymer backbone.