Classical Metallocenes as Photoinitiators for the Anionic Polymerization of an Alkyl 2-Cyanoacrylate

Abstract

The classical metallocenes, ferrocene and ruthenocene, dissolve readily in neat ethyl 2-cyanoacrylate (CA) monomer. The electronic spectra of the resulting solutions display a near-ultraviolet absorption band assigned as a charge-transfer-to-solvent (metallocene → CA) transition. Irradiation into this band causes the one-electron oxidation of the metallocene to the corresponding metallocenium cation accompanied by reduction of CA to its radical anion. Addition of the latter species to CA initiates the anionic polymerization of the electrophilic monomer. The progress of photoinitiated polymerization was monitored in real time by attenuated total reflectance infrared spectroscopy.