MODEL-COMPOUND STUDIES OF SMALL BANDGAP CONJUGATED POLY(HETEROARYLENEMETHINES)

Quinoid thiophene oligomers 6, 7, and 8 were prepared and characterize d as model compounds of small bandgap polymers and were shown to have solid state bandgaps in the range of 1.31-2.15 eV and a lowest energy solution optical absorption maximum (lambda(max)) of 480-676 nm. It wa s found that the bandgap and ionization potential decrease and electro n affinity increases with increasing size of the quinoid oligomer. The se results of the model compound studies are in agreement with theoret ical predictions for the electronic properties of polythiophene with q uinoid geometry and suggest that small bandgap polymers can be achieve d by direct incorporation of quinoid structure in the polymer backbone .