A Study of the Scope, Limitations and Kinetics of the Siliconization of Triarylamines Using Tris(pentafluorophenyl)borane Catalysis

Piers-Rubinsztajn (P-R) conditions, involving catalysis by tris(pentafluorophenyl)borane, were applied to siliconize triarylamines. A phenylated linear methylhydrosiloxane copolymer was utilized to create a hydrolytically-stable composite with promising optical, electrochemical and thermal properties. However, the reaction was highly exothermic, had rapid uncontrollable kinetics and produced methane as a byproduct; problematic characteristics for larger scale syntheses. Thereafter, triarylamines with bulkier substituents were studied to determine whether the kinetics could be slowed and a less volatile byproduct created. The rate of conversion was retarded significantly as expected, but not all derivatives reacted quantitatively in ambient conditions. Finally, P-R conditions were applied to methylhydrosiloxane-dimethylsiloxane copolymers. Gelation in air upon extended reaction time was effectively avoided by “finishing” excess Si-H sites using anisole. The result was the preparation of composites with up to 61 wt % arylamine content, which are expected to have significant applications as cost-effective flexible hole transport layers in organic electronic devices.MAS