Design and fabrication of organic-based interfacial films

Abstract

Interface engineering is of great interest in the field of chemistry and materials science, because the properties of its interface determine the properties of an object in a crucial fashion. Interfacial film, formed with tailor-made functional group, could control the physicochemical properties of interfacial systems and endow extrinsic properties. Due to its potential abilities, various interfaces including surface, cell interface, and fluidic interface have been engineered with functional materials. In relation to this, the chemistry between the target interfaces and coating materials should be considered in advance and the various parameters of the formed films, such as stiffness and elasticity, thickness and porosity, should be designed for purpose. In this thesis, various interfacial systems have been designed based on organic molecules, and can be categorized as follows. (1) Cell-interface engineering with reactive layer-by-layer (LbL) deposition: LbL technique was combined with bioinspired mineralization for formation of silica and iron oxide films on living-cell surface. Polyamine utilized as catalytic template for reactive LbL deposition of inorganic species, and thickness of resulting films was tightly controlled in nanometer scale with number of deposition cycles. Growth and division of encapsulated cells was controlled with thickness-dependent manner and incorporation of magnetic nanoparticles during the reactive LbL process further allowed spatiotemporal manipulation of living cells as living magnets. (2) Fluidic-interface engineering with oxidative assembly of Fe(II)-tannin complex: steady oxygen ($O_2$)-induced oxidation of Fe(II) to Fe(III) in the preformed Fe(II)-tannin complex at and/or near the $O_2$-enriched fluidic interface (i.e., air-water interface), generating interface-active Fe(III)-tannin species in situ, led to the formation of micrometer-thick Fe(III)-tannin films, which were transferable, self-healable, pliable, and post-functionalizable. Their in situ generation and self-assembly at the oil-water interface also demonstrated by oil-in-water (o/w) emulsion stabilization and concurrent capsule formation with on aid of surfactants. Although a wide scope of interfacial films was demonstrated in this thesis, the primitive essences are based on surface chemistry that highlights the coating methods, including layer-by-layer assembly, bioinspired mineralization and supramolecular self-assembly. In following sections, each of the designed interfacial systems is reported in term of the chemical insight they provide as well as their applications.