Band gap modifications in functionalized poly(methylphenylsilanes)

For many applications of polysilanes in optoelectronic devices, it is desirable that polymer properties, such as their band gap energy levels, their (redox) stability, and their propensity to interact favorably with (semi)conducting inorganic substrates, can be tailored. It has been demonstrated that, by introduction of substituents in the aryl moiety of poly(methylphenylsilane) (1), i.e., poly(methyl-4-methylphenylsilane) (2), poly(4-methoxyphenylmethylsilane) (3), poly[4-(dimethylamino)phenylmethylsilane] (4), poly(3-methoxyphenylmethylsilane) (5), and poly[4-(2-methoxyethoxy)phenylmethylsilane] (6), these objectives can be achieved. For comparative purposes, poly(4,7,10,13-tetraoxatetradecylmethylsilane) (7) was also taken into consideration. Electrochemical measurements (cyclic voltammetry) in THF/LiClO4 of 1−7 show that the onset of oxidation Vi of each polysilane provides a reliable estimate of its valence band edge; within series 1−7 Vi shifts over ca. 0.7 V. Although it is impossible to obtain a r...