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One way of measuring adhesion forces in fine powders is to place the particles on a surface, retract the surface with a high acceleration, and observe their detachment due to their inertia. To induce detachment of micrometer-sized particles, an acceleration in the order of 500,000g is required. We developed a device in which such high acceleration is provided by a Hopkinson bar and measured via laser vibrometry. Using a Hopkinson bar, the fundamental limit of mechanically possible accelerations is reached, since higher values cause material failure. Particle detachment is detected by optical video microscopy. With subsequent automated data evaluation a statistical distribution of adhesion forces is obtained. To validate the method, adhesion forces for ensembles of single polystyrene and silica particles on a polystyrene coated steel surface were measured under ambient conditions. We were able to investigate more than 150 individual particles in one experiment and obtained adhesion values of particles in a diameter range of 3-13 μm. Measured adhesion forces of small particles agreed with values from colloidal probe measurements and theoretical predictions. However, we observe a stronger increase of adhesion for particles with a diameter larger than roughly 7-10 μm. We suggest that this discrepancy is caused by surface roughness and heterogeneity. Large particles adjust and find a stable position on the surface due to their inertia while small particles tend to remain at the position of first contact. The new device will be applicable to study a broad variety of different particle-surface combinations on a routine basis, including strongly cohesive powders like pharmaceutical drugs for treatment of lung diseases.

The microphase orientation/reorientation alignment kinetics behaviour of lamellar PS-b-PB diblock and PS-b-PB-b-PS triblock copolymers under LAOS conditions is studied. By online monitoring the degree of the mechanical nonlinearity during the orientation process, as determined via the higher harmonics in FT rheology [i.e: I 3/1 (t), ∅ 3 (t)], and investigation of the orientation distribution by 2D-SAXS, the kinetics of the microphase alignment for different experimental shear conditions was followed. For di- and triblock copolymers, the shear orientation into parallel alignment is possible and the kinetics of orientation is strongly dependent on the strain amplitude.

Polymer brush coatings are well-known for their ability to tailor surface properties in a wide range of applications from colloid stabilization to medicine. In most cases, the brushes are used in solution. Consequently, efforts were expended to experimentally investigate or theoretically predict the swelling behavior of the brushes in solvents of different qualities. Here, we show that the micromechanical cantilever (MC) sensor technique is a tool to perform time-resolved physicochemical investigations of thin layers such as polymer brushes. Complementary to scattering techniques, which measure the thickness, the MC sensor technique provides information about changes in the internal pressure of the brushes during a swelling and deswelling process. We show that the kinetics of both swelling and deswelling are dependent on solvent quality. Comparing the measured data with its thickness evolution, which was calculated based on the Flory-Huggins theory, we found that only the first 10% of the thickness increase of the polymer brush results in a significant pressure increase inside the polymer brush layer.

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 graftin 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.

Structure formation in a multicomponent ultrathin polymer blend film was investigated at and below the surface with grazing incidence X-ray and neutron scattering and scanning force microscopy (SFM). Two films were examined. First a strongly incompatible binary polymer blend film in which a buried structure was clearly identified. This binary blend film then was compared with a ternary blend film into which 5 wt% of a compatibilizing copolymer had been added. The addition of the compatibilizer was found to decrease the size of the internal structures, while leaving the surface morphology unchanged.

The surface topography and the chemical morphology of poly(styrene-block-paramethylstyrene) diblock copolymers confined within isolated drops are investigated. The drop geometry imposes a two-dimensional spatial restriction. With scanning force microscopy, the film thickness dependence of the mean drop distance as the basic topographical feature is determined. In addition to large drops, a second smaller droplet structure is observed among the drops. The comparison of grazing incidence small-angle scattering using X-rays and neutrons shows that inside the drops the diblock copolymer orients into perpendicular lamellae with respect to the substrate surface. Compared to the bulk, the lamellar spacing is stretched parallel to the substrate.

Ordered 2D-arrays of TiO 2 nanoparticles were synthesised by a poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) block-copolymer templated sol–gel process within a thin polymer film. The order within the filled polymer films was found to depend on the sol–gel content during synthesis. Grazing incidence small angle X-ray scattering and scanning electron microscopy imaging proved that well-ordered structures were created over large areas of the thin hybrid film.