Partially crystalline TiO 2 was deposited on polystyrene substrates by liquid phase deposition. Both nucleation and adhesion depend on the respective pretreatment of the polymer. Coherent films are formed on untreated substrates and surfaces hydroxylated by aqueous sodium peroxodisulfate solution, but satisfactory film adhesion is only observed on the modified surface. The formation of continuous films is not observed on polystyrene etched by H 2 SO 4 /SO 3 where material deposition was only initiated at few nucleation sites. The TiO 2 precipitation was characterized as a function of time and compared to previous results on wet chemically grafted PS. A film formation mechanism is proposed which can account for the textured constitution of TiO 2 observed by X-ray diffraction experiments.

Polystyrene (PS) substrates were functionalized by wet chemical grafting with 2-acrylamido-2-methylpropane-1sulfonic acid (AMPS). Subsequently, TiO 2 thin films were prepared by liquid phase deposition (LPD) with an average growth rate of 85 nm h 21 ; a maximum thickness of 750 nm was observed in our experiments. The crystalline fraction of the precipitated material was estimated to be 58% by X-ray powder-diffraction. Significantly improved film adhesion was achieved on grafted substrates, as compared to non-functionalized polymers, due to the formation of a thin, coherent primer layer in the early stages of mineralization.

Nextel™ 610 multifilaments were continuously coated with aqueous sols of yttria‐stabilized zirconia (8YSZ). For the transformation of the sol–gel precursor to a crystalline oxide coating detailed microstructural characterization is given. The main subject of the study was the bridging of fibers by interphase material, a general phenomenon of sol–gel coatings. A three‐point bending test is proposed as a semi‐quantitative method to determine the characteristic stiffening of bridged fiber bundles. This method is successfully used to evaluate the influence of sol concentration on fiber bridging and to prove the benefit of additional surfactants to aqueous sols. Differences in film formation on the individual fiber surfaces leading to homogeneous or inhomogeneous film thickness and variation in degree of fiber surface coverage are explained with a three‐fiber model. Based on model and experiment it is shown that even surface coverage and homogeneous film thickness can better be accomplished by multiple coatings from low concentrated sols than by single coatings from high concentrated sols. Finally, the three‐point bending test is used to qualitatively investigate the mechanical properties of the material bridges which can be correlated with results from structural investigations.

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