With specular and off-specular X-ray scattering the surface morphology in terms of surface roughness, film quality, and roughness correlation in thin polymer films of polystyrene and fully brominated polystyrene is measured. During the preparation of the thin films on top of silicon substrates, the common solvent was varied. We investigated eight different solvents and three different solvent mixtures to depict the influence of typical solvent parameters. In the regime of a small solvent vapor pressure, we observed correlated roughness as the ultimate lower limit of accessible surface smoothness. The resulting films are homogeneous, and the surface roughness is given by the substrate. In an intermediate vapor pressure regime marked surface morphologies are detected, while at a high vapor pressure smoother films result again.

High-density arrays of titania nanoparticles were prepared using a polystyrene-b-poly(ethylene oxide) block copolymer (PS-b-PEO) as a template and a titanium tetraisopropoxide based sol-gel precursor as titania source via a spin-coating method. The hydrophilic titania sol-gel precursor was selectively incorporated into hydrophilic PEO domains of PS-b-PEO and form titania nanoparticle arrays, due to a microphase separation between the PS block and the sol-gel/PEO phase. Field emission scanning electron microscopy (FESEM) and scanning probe microscopy (SPM) images showed that the uniformity and long-range order of the titania/PEO domains improved with increasing sol-gel precursor amount. Grazing incidence small-angle X-ray scattering (GISAXS) results indicate that the ordered structures exist over large length scales. Titania nanocrystal arrays of anatase modification were obtained by calcination at 600 degrees C for 4 h. After calcination, separated particles were observed for low and medium amounts of sol-gel precursors. Films with higher precursor amounts showed wormlike structures due to the aggregation between neighboring particles. Removal of the polymer matrix via UV treatment leads to highly ordered arrays of amorphous titania while retaining the domain size and interparticle distance initially present in the hybrid films. Photoluminescence (PL) properties were investigated for samples before and after calcination. The PL intensity increases with the increasing amount of sol-gel precursor. Bands at 412 nm were ascribed to self-trapped exitons and bands at 461 and 502 nm to oxygen vacancies, respectively. Uncalcined or UV-treated samples also showed PL properties similar to calcined samples, indicating that the local environment of the titanium atoms is similar to the environment of the crystalline anatase modification.

Summary: A technique to cover microelectromechanical systems (MEMS), such as micromechanical cantilever (MC) sensors, with a covalently bound brush layer has been developed. The polymer layer was grown using a “grafting‐from” synthesis of polymer brushes under mild conditions, by surface‐initiated atom transfer radical polymerization. Atomic force microscopy (AFM) and ellipsometry have revealed a uniform thickness of about 12 nm from which a grafting density of polymer brushes of 0.19 chains · nm−2 was estimated. The coating with polymer brushes can be realized on a selected surface. It was shown that a single‐sided brush layer swells reversibly in toluene, resulting in a bending of the micromechanical cantilever.Schematic representation of the PMMA brush synthesis on the MC surface, by surface‐initiated ATRP.magnified imageSchematic representation of the PMMA brush synthesis on the MC surface, by surface‐initiated ATRP.

Dynamics and microstructure of the surfactant layer in organically modified silicates and their composites with polystyrene were studied as a function of surfactant loading and temperature in the range relevant for melt intercalation. Site selectivity was achieved by using specifically headgroup-and tail-labeled surfactant EPR spin probes and by applying 31 P MAS NMR to phosphonium surfactants. Bimodal dynamics is observed over a broad range of surfactant loadings and temperatures in both the absence and presence of polymers and correlates with a bimodal distribution of surfactant headgroup distances from the silicate surface. Excess surfactant with respect to the cation exchange capacity of the silicate plasticizes the surfactant layer. Electron spin echo envelope modulation on nanocomposites with ammonium surfactant and deuterated polystyrene demonstrates close contact between the polymer and surfactant tail ends. Surfactant dynamics changes strongly during microcomposite formation, i.e., by embedding stacks of organoclay platelets in a polymer matrix, even if no intercalation takes place.

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