Coupled-PDMS grafted mesoporous γ-alumina membranes for solvent nanofiltration

In this paper grafting of mesoporous c-alumina membranes with hydride terminated polydimethylsiloxane is described. Vinyltriethoxysilane is used as linking agent and tetrakis(vinyldimethylsiloxy)silane as a coupling agent, to create a dense network structure that is grafted in the ceramic pores. Grafting performance of the organic moieties on c-alumina powders was analyzed by FTIR and TGA. The results indicate that grafting reactions were successfully carried out. Contact angle analysis on the grafted membranes showed that grafting occurs on the c-alumina layer and that the resulting membrane surface had a water contact angle of 108 . From permeability and rejection tests using Sudan Black in toluene, ethyl acetate or isopropanol, the use of a coupling agent was found to result in a more dense network structure grafted in the gamma alumina pores. This resulted in a higher rejection for nanofiltration of solvents but at the cost of a lower solvent permeability, when compared with PDMS-grafted alumina membranes where no coupling of PDMS was applied

Chemical modification/grafting of mesoporous alumina with polydimethylsiloxane (PDMS)

A method for polydimethylsiloxane grafting of alumina powders is described which involves chemical modification of the surface of mesoporous (5 nm) γ-alumina flakes with a linker (3-aminopropyltriethoxysilane: APTES), either by a solution phase (SPD) or a vapour phase (VPD) reaction, followed by PDMS grafting. The systems were analysed by FTIR, gas adsorption/desorption and TGA. Grafting is proven by FTIR for all cases, meaning that a covalent bond exists between inorganic particle and organic moiety. It is demonstrated that the way of applying APTES (by SPD or VPD) has an effect on the morphology of linker as well as of PDMS. A more controlled grafting of the APTES linker on γ-alumina is possible by the VPD method, resulting in efficient grafting and good infiltration of PDMS in the pores of the inorganic system. Stability tests on these PDMS grafted alumina show no degradation after 14 days soaking in a wide range of solvents. Surface modification of metal oxide particles by organic moieties via a chemical reaction can adapt its interfacial properties and renders a high chemical stability of these inorganic-organic hybrids. This validates the use of these materials under severe applications like in membranes for solvent nanofiltration or for protein immobilization and resin modification in e.g. chromatographic applications

Production and characterization of miro- and nano-features in biomedical alumina and zirconia ceramics using a tape casting route

A process of micromolding, delivering micro- and nanopatterned ceramic surfaces for biomaterial applications is described in this work. To create the desired structures, tape casting of ceramic slurries on microfabricated silicon mold was used. Several tape casting slurry compositions were tested to evaluate the feasibility of transferring micro- and nano-features from silicon molds. Used ceramics were alumina (α-Al2O3) and yttria stabilized zirconia. Three types of polymeric binders for the green tape (PVB, PES, and PVP) were investigated using three different solvents (ethanol, n-methyl-pyrrolidone, water). Well-defined features in shapes of wells with diameters down to 2.4 μm and a depth of 10 μm and pillars with diameters down to 1.7 μm and a height of 3 μm were obtained. Morphology, grain size and porosity of the sintered bodies were characterized. Finally fibroblast cells were cultured on the surfaces in order to observe their morphology under influence of the microstructured surfaces