Steady-State and Time-Resolved Spectroscopic Characteristics of Novel Silicon-Containing Organopolymers

Abstract

The spectroscopic characteristics of novel π-conjugated polymers containing four-coordinated silicon, acetylene groups and either 1,4-biphenylene or 2,7-fluorene in the main chain were investigated by steady-state and picosecond laser spectroscopy. The spectral features of absorption, fluorescence excitation spectra, fluorescence lifetime, and fluorescence polarization were explained by the existence of two kinds of inhomogeneously broadened electronic states formed in the disordered polymeric chain. The dynamics of photoinduced absorption was measured in the 400–900 nm spectral range with picosecond time resolution. The long-wavelength band with λ_max ∼ 710 nm was ascribed to excited-state absorption from higher-lying electronic states created in short polymeric segments with essential conformational distortion of the subunits. The short-wavelength band with λ_max ∼ 580 nm and a shoulder at 500 nm was interpreted as photoinduced absorption from a lower-lying state arisen in more planar, longer π-conjugated segments populated via direct excitation and energy migration between disordered segments of the polymeric chain. For the fluorene-containing polymer, the smaller Stokes shift and the greater degree of fluorescence polarization are consistent with more extensive electron delocalization along the backbone.