Energy transfer polysilanes

The electronically excited states of the emitter can be populated via direct ex-citon formation at the emitter molecule. Alternatively, the electronic properties of polysilanes facilitate an energy transfer from excited states of the polysilane to the emitter molecule. 

Polysilanes are also applicable as matrix materials in phosphorescent OLEDs. Mixtures of polysilanes and triplet emitters are sufficient to effect an energy transfer from polysilane triplet states to emitter triplet states, thus amplifying the luminescence of the device. It has been shown that if polysilanes have electrophosphorescent side chains consisting of triplet emitters, the energy transfer from polysilane to emitter is most effective [124]. Thus the beneficial electronic properties of polysilanes are perfectly combined with the spectroscopic properties of transition metal based triplet emitters. The compounds described are derivatives of polymethylphenylsi-lanes, (Fig. 24) which are covalently attached to triplet emitters with iridium as metal centre. The polymers were applied in OLEDs with an ITO/active layer/Ca/Ag layer sequence. The active layer contained a fraction of 70% by weight of the... 

Sonochemical homopolymerization of dichlorosilanes in the presence of sodium is successful at ambient temperatures in nonpolar aromatic solvents (toluene or xylenes) only for monomers with a-aryl substituents. Dialky 1-dichlorosilanes do not react with dispersed sodium under these conditions, but they can be copolymerized with phenylmethyldichlorosilane. Copolymers with a 30-45% content of dialkylsilanes were formed from equimolar mixtures of the corresponding comonomers. Copolymerization might indicate anionic intermediates. A chloroterminated chain end in the polymerization of phenylmethyldichlorosilane can participate in a two-electron-transfer process with sodium (or rather two subsequent steps separated by a low-energy barrier). The resulting silyl anion can react with both dichlorosilanes. The presence of a phenyl group in either a or P position in chloroterminated polysilane allows reductive coupling, in contrast to peralkyl species, which do not allow the reaction. Therefore, dialkyl monomers can copolymerize, but they cannot homopolymerize under sonochemical conditions. 

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