Many functional complexes in biology have highly hierarchic structures, as can be seen in various biological systems such as organelles, cells, tissues, and organs. In these systems, hierarchy is important in relaying events at different structural dimensions resulting in harmonized functions. Therefore, the development of biological mimics with hierarchic structures is believed to be useful for construction of highly functional materials. We are creating various supramolecular systems from molecular to materials levels and have recently successfully merged two paradigms of the self-assembly domain, that is mesoporous fabrication and layer-by-layer (LbL) assembly, to create functional hierarchic structures that co-possess characteristics of both: highly-precise pore geometries and organized layered structures. The obtained hierarchic structures can be used for biorelated applications including biosensing and drug delivery. For example, LbL assembly of mesoporous carbon CMK-3 was performed on a quartz crystal microbalance (QCM) plate with the aid of poly(diallyldimethylammonium chloride) for sensor application. Addition of tannic acid induced immediate and substantial reduction of frequency, indicating a strong adsorption of tannic acid onto the mesoporous carbon LbL film coated on the QCM. This selective adsorption capacity for tannic acid likely originates in strong interactions between carbon and tannic acid in CMK-3 pores probably through p–p interactions and hydrophobic effects. In another example, mesoporous silica capsules were assembled into hierarchical layered structures on a QCM plate through LbL assembly with the aid of silica nanoparticles and cationic polyelectrolyte. Surprisingly, the frequency shift upon drug release from the films exhibited a stepwise profile even though no external stimulus was applied. A plausible mechanism for auto-modulation of drug release from the films is assumed to originate from combination of two processes: water evaporation from the pores and capillary penetration into the pores. In addition, sensor application of LbL films of mesoporous carbon structures were also investigated. Coupling of mesoporous materials technologies and LbL assembly will introduce methods for construction of well-designed and integrated nano- and microstructures beyond the individual categories of soft matter and hard materials.

Mesoporous materials in layer-by-layer architectures for sustainable developments

249th National Meeting (2015)

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