| Abstract
| - New amphoteric, amino acid bifunctional mesoporous silicas with highly ordered mesopores weresynthesized via the cooperative self-assembly of surfactants, co-structure-directing agents (CSDA), anda silica source. Uniform distributions of acid and base organic groups on the mesopore surfaces wereformed by interactions between the counter charged surfactant head groups and ionic parts of CSDAs,that is, between the cationic and anionic surfactant head groups and the carboxyl and amino groups ofCSDAs, respectively. For structural determination, the materials were characterized using X-ray diffraction(XRD), high-resolution transmission electron microscopy (HRTEM), and N2 sorption measurements. Ithas been demonstrated that organic (NH2 and COOH) pairs incorporated in the mesopore walls behaveas amino acids, collectively exhibiting an isoelectric point, pI, of ∼6.0, a value close to that of a neutralamino acid. Further, the amphoteric amino acid moiety can be switched readily in a moment from netcationic and acidic to net anionic and basic by simply increasing the pH of the solution. Loading of theNH2 and COOH groups was controlled at an almost equal basis of ca. 1.0 and 0.9 mmol/g SiO2,respectively. Close adjacency of organic NH2 and COOH groups was confirmed by the formation ofamide moieties. The basic idea employed here will be easily and widely applicable to the design ofrelevant mesoporous materials.
- Amphoteric amino acid bifunctional, well-ordered mesoporous silicas were synthesized by the co-structure-directing method. Uniform distributions of organic groups were formed by interactions between the surfactant head groups and ionic parts of CSDAs. It is demonstrated that the NH2 and COOH pairs incorporated in the mesopore walls behave as amino acids.
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