New conjugated polymer/sol‐gel glass composites: Luminescence and optical waveguides

Abstract

mospheric contamination. The preparation method was ordinary spin-coating in a laboratory atmosphere.A forthcoming publication will elucidate the growth mode of the same system with a different application technique, i.e. dip-coating. In this case, i.e. with no centrifugal acceleration present, there is no layer-by-layer growth. ExperimentalThe chemical surface constitution of the silicon wafers was investigated by XPS (VG ESCALAB MK2 and 22Oi-XL) and AES (Perkin Elmer PHI 660). The wafer surface and the film thickness of the applied organic films were monitored [8] by means of the ellipsometer Auto EL 11, Rudolph Res. The morphology of the wafers and films was imaged with the Nanoscope 111 Multimode AFM (Digital Instruments) in the Tapping Mode with minimized force in air by means of silicon cantilevers (Nanosensors, L.O.T.Orie1) having a nominal tip radius of less than 10 nm. Each tip was characterized before and after imaging by means of calibration samples to avoid artifacts in imaging.The prepolymer was dissolved in l,l,l-trichloroethane to allow the application out of solution. In order to obtain different mean film thickness, the concentration was varied from 0.002 to 0.2 mg/mL). For spin-coating, the wafers were mounted horizontally on the spin-coater (laboratory atmosphere), fully wetted with the prepolymer solution, and after a pause of 3 s, accelerated to So00 rpm. During the rotation time of 15 s the film suddenly changed color, indicating the evaporation of the solvent. The convolution between AFM tip and sample (W. Hanrieder, R.Mock, H. Meixner, Ultramicroscopy 1992,4244,169) will not hamper the determination of heights as long as access to the height levels to he compared is given. This procedure neglects the convolution between AFM tip and sample (Ref.[lo]), which results in an over-estimation of the area fraction of protrusions and in an under-estimation of the area fraction of depressions.

The chemistry of electroluminescent organic materials

“…Thus, chemical vapor deposition (CVD), which provides a clean environment as a solvent-free and low temperature process that is well suited to sequential deposition [32], has been employed to prepare pinhole-free films of PPV that are amorphous or nanocrystalline and which show a glass transition [33]. The sol-gel technique [34] has been applied to the preparation of PPV/sol-gel composites [35] in order to improve the lifetime and efficiency and to tune the emitting high frequency of devices. Other groups have concentrated on using the Langmuir-Blodgett (LB) technique [36] to prepare highly ordered thin films with precise control of the film thickness [37].…”

Fluorene Based Conjugated Polyelectrolyte/Silica Nanocomposites: Charge‐Mediated Phase Aggregation at the Organic–Inorganic Interface

“…For the many reasons presented above, the preparation of CP/inorganic hybrids has attracted significant attention and some of the methods investigated to date include encapsulation of CP nanoparticles in silica shells,17, 18 in‐situ polymerization of water‐soluble monomer precursors within a sol‐gel matrix,19, 20 and silyl‐functionalisation of the organic CP component to inhibit phase separation 21. Recently, Frey and co‐workers achieved a 15 nm conjugated polymer/titania phase separation using non‐aqueous sol‐gel processing conditions in the presence of a structure‐directing agent 7, 8.…”

Nanocomposites

“…The first report on such a PPV-silica composite created by the sol-gel process was published by Wung et al (1991), who reported the preparation of films of thicknesses in the micrometer range. Since then there have also been other reports on nonlinear optical properties (Davies et al, 1996) and fluorescence studies (Faraggi et al, 1996) of these composites.…”