Photostructural modifications in poly(methylphenylsilylene) thin films: Excitation wavelength and atmosphere dependence

Electronic (UV-vis) and vibrational absorption spectroscopies were used to examine the impact of incident photon energy and local atmospheric composition on the development of photo-induced structural changes in poly[(methyl)(phenyl)silylene] thin films. The relative impact of atmosphere on the magnitude and nature of photostructural modifications in this material is found to be enhanced under 3.68 eV photon exposure where the incident photon is resonant with the lowest energy absorption of the Si-Si-conjugated backbone structure. This is in contrast to a greater overall magnitude of photo-induced structural change, with limited atmospheric dependence, observed under 5.1 eV exposure, resonant with absorption transitions associated with the π-conjugated phenyl ring side group. These results provide insight into the underlying structural mechanisms contributing to the large refractive index changes typically observed in these materials.