Synthesis and characterization of poly(tetramethylsilarylenesiloxane) derivatives bearing benzodithiophene moieties

Poly(tetramethylsilarylenesiloxane) derivatives bearing benzo[1,2-b;4,5-b′]dithiophene (P1) and benzo[2,1-b;3,4-b′]dithiophene (P2) moieties were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,6-bis(dimethylhydroxysilyl)benzo[1,2-b;4,5-b′]dithiophene (M1) and 2,7-bis(dimethylhydroxysilyl)benzo[2,1-b;3,4-b′]dithiophene (M2), respectively. It was deduced that P1 is a crystalline polymer while P2 is an amorphous one from the results of differential scanning calorimetry (DSC). Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra when dimethylsilyl substituents were introduced on the benzo[1,2-b;4,5-b′]dithiophene and benzo[2,1-b;3,4-b′]dithiophene skeletons. The fluorescence quantum yields (ΦFs) were not improved by the introduction of dimethylsilyl groups onto the benzo[1,2-b;4,5-b′]dithiophene and benzo[2,1-b;3,4-b′]dithiophene skeletons, whereas the improvement in the ΦFs was remarkable in the case of poly(tetramethylsilarylenesiloxane) derivatives that possessed the corresponding fused benzene ring systems, i.e., poly(tetramethyl-2,6-silanthrylenesiloxane) and poly(tetramethyl-1,8-silphenanthrylenesiloxane).