Regular sigma-pi organosilane copolymers with alternating oligomeric dimethylsilylene and cis or trans stilbene units

A series of perfectly alternating copolymers containing oligomeric dimethylsilylene and cia or trans stilbene units has been prepared by the condensation polymerization of silyl ditriflates with the corresponding stilbene dianion. As expected, the spectral characteristics and the polymer processability were very different for the isomeric polymers. Evidence of sigma-pi interaction was obtained from absorption measurements and the excited state of the Si-4 catenates was characteristic of a polar charge transfer state. The polymers are all photoactive and irradiation in the long-wavelength absorption band leads to cis-trans isomerization followed by complete disappearance of the long-wavelength (lambda > 300 nm) absorption. The latter was not observed for the monomeric model compounds.