Polydimethylsiloxane [PDMS]-modified SiO2-TiO2, glasses have been prepared via the sol-gel route. Polymer compositions varied between 17 and 67 wt% PDMS, using PDMS of molecular weights 1,700 and 36,000. Also varied was the Si/Ti ratio for a given polymer content and the nature of the Ti alkoxide.A general synthetic procedure was found which made optically clear samples. Dense monolithic structures were obtained at room temperature for all compositions. The room temperature densification is attributed to relaxation and flow in the sample due to the presence of the polymer. The effects on properties of the overall composition and molecular weight of the polymer are reported, and implications in terms of structural models are considered.
When preparing the active layer film for organic optoelectronic devices, e.g., solar cells, spin-coating is often used for the deposition of the solution of electron donor and acceptor molecules. An alternative, among others, is to use dipcoating, where the substrate is dipped into the solution and subsequently withdrawn, all at coordinated speeds and times. In order to develop knowledge on how the final active layer morphology is influenced by preparation parameters, different coating methods are compared. In this contribution, we report on a comparative study of thin deposited films from a model system. The investigated model system is poly(9,9-dioctylfluorene) (F8, also referred to as PFO) as donor and [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 60 BM) as acceptor. Combining fluorescence and absorption spectroscopy with atomic force microscopy allows us to conclude that dipcoating offers increased possibilities to manipulate the film morphology, that the transition of the glassy F8 α-phase to the more ordered β-phase is influenced by the dipping speed as well as by the blend ratio, and that the long-wavelength emission of F8 cannot stem from the oxidized keto-F8 only.
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