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New approaches to the fabrication of microstructures of special shape were developed for polymers. Unusual superhydrophobic surface structures were achieved with the use of flexible polymers and hierarchical molds. Flexible polyurethane−acrylate coatings were patterned with microstructures with use of microstructured aluminum mold in a controlled UV-curing process. Electron microscope images of the UV-cured coatings on polymethylmethacrylate (PMMA) substrates revealed micropillars that were significantly higher than the corresponding depressions of the mold (even 47 vs. 35 μm). The elongation was achieved by detaching the mold from the flexible, partially cured acrylate surface and then further curing the separated microstructure. The modified acrylate surface is superhydrophobic with a water contact angle of 156° and sliding angle of Acrylic thermoplastic elastomers (TPE) were patterned with micro−nanostructured aluminum oxide molds through injection molding. The hierarchical surface of the elastomer showed elongated micropillars (57 μm) with nail-head tops covered with nanograss. Comparison with a reference microstructure of the same material (35 μm) indicated that the nanopores of the micro−nanomold assisted the formation of the nail-shaped micropillars. The elasticity of the TPE materials evidently plays a role in the elongation because similar elongation has not been found in hierarchically structured thermoplastic surfaces. The hierarchical micronail structure supports a high water contact angle (164°), representing an increase of 88° relative to the smooth TPE surface. The sliding angle was close to zero degrees, indicating the Cassie–Baxter state.

Micropit surfaces and hierarchically structured micropit/nanodepression surfaces were fabricated in polypropylene by injection moulding. The first step in the process was the microstructuring of aluminium foils with a micro-working robot to obtain a pattern of micropits. Dimensions of the micropits could be controlled by adjusting the working parameters of the robot. The microstructured faces of some of the foils were anodized to aluminium oxide giving a surface in which both micropits and the smooth areas between were covered with nanopores. Mould inserts for the injection moulding were obtained by cold mounting of an epoxy resin mixture on the foils. After the epoxy resin had hardened, the foils were etched away. Dimensions of the micropillars and micropillars/nanobumps on the epoxy related to the dimensions of the structures on the foils. Finally, structures were replicated in polypropylene as micropits and hierarchical micropits/nanodepressions by injection moulding. The dimensions of these hollow structures corresponded well with those of the epoxy pillars and the original micropits. Static and dynamic contact angles on the micropit-structured polypropylene surfaces were elevated from the slightly hydrophobic values of smooth polypropylene. With hierarchical micropit/nanodepression structures, the contact angles approached the superhydrophobic limit of 150°. The work demonstrates an inexpensive and reproducible technique to fabricate hollow structures of various dimensions and scales on polypropylene and modify the surface properties of the polymer.

Anisotropically microstructured and hierarchically micro/nanostructured surfaces were fabricated on polypropylene by injection moulding. Microstructured mould inserts were obtained by structuring electropolished aluminium foils with a micro-working robot, and hierarchically structured mould inserts by anodizing the microstructured aluminium foils. On both types of inserts, the microstructures were anisotropic, consisting of alternating smooth and microstructured zones. Anisotropy, and other properties of microstructures, can be controlled by adjusting the parameters of the micro-working robot. The mould inserts were used to prepare micro- and hierarchically structured polypropylene discs by injection moulding. Replication accuracy at both structure levels can be controlled through the moulding conditions. The behaviour of water on the structures was characterized by measuring the contact and sliding angles parallel and perpendicular to the microstructured zones. Surfaces with microstructures alone were highly hydrophobic, where water droplets adopted the Wenzel state and had clearly different parallel and perpendicular contact angles. Surfaces with dual structures had contact angles near 170° and sliding angles near 0°, and again the angles in parallel and perpendicular directions differed. Superhydrophobic, anisotropic Cassie–Baxter state was achieved.

Density functional approach was applied to study adsorption of dirhenium decacarbonyl on γ-alumina (1 1 0). Two different surface O-bridges were considered as an active site; the first site has an oxygen atom between two octahedrally coordinated aluminium whereas the second adsorption site includes O-bridge between octahedrally and tetrahedrally coordinated aluminium. The stepwise decarbonylation of Re2(CO)10 on alumina cluster model was studied. The interactions energetics of rhenium subcarbonyls (Re2(CO)9, Re(CO)4 and Re(CO)3) on alumina surface were investigated. The results reveal that there is a correlation between calculated interaction energies and earlier experimental desorption studies.

In the present work, the first interaction steps of Group VI hexacarbonyls with different surface sites of alumina were modelled by a computational, non-local, density-functional theory method. Octahedral and tetrahedral Lewis acid sites were considered as active sites for M(CO) 6 (M=Cr, Mo, W) adsorption. An interaction with a Lewis base site took place with the cleavage of one CO ligand of the metal carbonyl and with the formation of the metaloxygen bond. The results show that the interaction is stronger with Lewis base sites than with acidic ones. On the Lewis base site, the interaction energy is higher for the octahedral aluminium coordination than for tetrahedral coordination. On the contrary, on a Lewis acid site, the interaction is stronger with the tetrahedrally coordinated aluminium. Neutralisation of Lewis base sites diminishes the interaction of the metal complex with the surface. Comparison of the results in the metal series reveals that chromium and molybdenum carbonyls interact with the surface sites similarly, while for the tungsten analogues the interaction is somewhat stronger.