ORGANOSILICON POLYMERS WITH ALTERNATING SIGMA-CONJUGATED AND PI-CONJUGATED SYSTEMS

A series of organosilicon polymers containing polysilane and diethynyl aryl units along the polymer backbone were synthesized and examined wi th respect to their optical absorptions. The results indicate that del ocalization takes place through the sigma-pi conjugated system. Length ening of pi-conjugation leads to lower excitation energies while nearl y identical UV-vis spectra are observed with increased Si-Si chain len gth. Introducing a thiophene unit into the pi-system instead of a benz ene unit leads to a bathochromic shift reflecting greater sigma-pi del ocalization. The polymers undergo photodegradation, probably via cleav age of the Si-Si bonds, and thermal crosslinking by reaction at the C= C triple bonds. When doped with iodine, these polymers become semicond ucting with conductivity of the order of 10(-4) S cm-1.