Abstract
We describe the synthesis of mesoporous Al2O3 and MgO layers on silicon wafer substrates by using poly(dimethylacrylamide) hydrogels as porogenic matrices. Hydrogel films are prepared by spreading the polymer through spin-coating, followed by photo-cross-linking and anchoring to the substrate surface. The metal oxides are obtained by swelling the hydrogels in the respective metal nitrate solutions and subsequent thermal conversion. Combustion of the hydrogel results in mesoporous metal oxide layers with thicknesses in the μm range and high specific surface areas up to 558 m2∙g−1. Materials are characterized by SEM, FIB ablation, EDX, and Kr physisorption porosimetry.
Highlights
The synthesis of metal oxides with uniform mesopores is often achieved by utilization of porogenic structure directors or matrices
Nanocasting can be used for the fabrication of a multitude of metal oxides, including Al2O3 [10,11,12], as well as those that have so far not been obtained by soft templating, e.g., magnesium oxide (MgO) [12,13,14,15]
The polymer for the hydrogels was synthesized by free radical polymerization of N,N-dimethylacrylamide (DMAAm) and 2-(dimethyl maleimido)-N-ethyl-acrylamide (DMIAAm) (Scheme 2a)
Summary
The synthesis of metal oxides with uniform mesopores is often achieved by utilization of porogenic structure directors or matrices. Micellar aggregates of amphiphilic species—such as surfactants or block co-polymers—are frequently utilized as porogens They form spontaneously by self-organization and serve as pore fillers or even as structure-directing species during the formation of the inorganic phase by a sol–gel-based synthesis (‘soft templating’) [1,2]. Continuous layers (‘solid films’) of mesoporous metal oxides at a substrate surface the soft-templating approach is usually the method of choice, because the spontaneous self-aggregation into micellar units can take place inside a liquid film that contains both the amphiphilic species and the inorganic precursor compounds For this purpose, the micellization is induced by evaporation of the solvent (evaporation-induced self-assembly, EISA) [6,7].
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