New Synthesis, Electroluminescence, and Photophysical Properties of Poly[(formylphenyl)methylsilanediyl] and Its Derivatives

A new one-step synthesis of formylated poly[methyl(phenyl)silanediyl] (PMPSi) is reported. The aldehyde groups were incorporated into the parent polymer by the reaction with dichloromethyl methyl ether in the presence of Lewis acid (SnCl 4 ). The reaction takes place via an unstable aryl(methoxy)methyl chloride intermediate. The new procedure is an important simplification of the known four-step synthesis of the poly[(formylphenyl)methylsilanediyl] via chloromethylation in the first step. The presence and reactivity of aldehyde groups in the polymer were proved by means of 1 H NMR, UV−vis, and FT IR spectroscopies. The reduction in relative molecular weight of the parent polysilane after reaction was not so pronounced as in the multistep synthesis. Model compounds N -benzylidene-1-aminopyrene, N -benzylidene-4-phenylaniline, and N -benzylidene-4-phenylazoaniline were synthesized for spectral characterization of the substituted polysilanes. The π-conjugated systems (pyrene, biphenyl, azobenzene) were attached to the σ-conjugated polysilane backbone. Photophysical properties, photostability, charge photogeneration, and photoluminescence of these materials were studied. Single- and double-layer light-emitting devices (LEDs) with emission in visible spectral region were fabricated. Their spectral and electrical characteristics were studied. Electroluminescence efficiency in double-layer LEDs reached the value of 0.03−0.06% and was more than 1 order of magnitude higher than that in single-layer devices (∼0.005%). Modified polysilanes exhibited better photostability than PMPSi and are particularly intended for the use in multilayer or blend devices.