The optical spectra of confined polygermanes: From bulk film down to nanosize layers

The monitoring of poly(di-n-hexylgermane) (PDHG) optical spectra in a variety of structures ranging from a polymer film to nanosize polymer filled porous media was performed by optical spectroscopy in the temperature range from 5 to 250 K. The PDHG nanocomposites were fabricated by insertion of PDHG polymers into SBA-15 mesoporous silica and SiO₂ porous films. Temperature dependence of the PDHG film fluorescence spectra shows that the polymer generally has disordered conformation while the random ordered segments behave as defects. The spectra of the composites correspond to the polymer chains with even less ordered segments and the aggregates of such chains. This is confirmed by the absence of the thermochromic transition in the composites contrary to the film. The difference between the optical spectra of the film and the composites is due to a decrease of both the intermolecular and exciton-phonon interactions in the composites. It was shown that the polymer chains in the SiO₂ pores are more ordered.