Ayae Sugawara

Calcium Carbonate–Organic Hybrid Materials

Thix article focuses on the synthetic approach to the preparation of calchim carbonare-organis hybrie materials, which are abtained by self-organisation processes under nuld conditions In these processes organic moleculessuch as functionalized polymers and aligned ampluphisic molecules on the surface play key roles in the orystallization of calcium carbonate, which results in the formation of hybrid materials. As welt as as being environmentally benign, the hybrid materials have concrolled more phology and unique properties. Materials scientists have obtained the ideas for the design of such hybrid materials from brominerals such as shells, teeth, and bones.

Hybrid Porous Materials with High Surface Area Derived from Bromophenylethenyl‐Functionalized Cubic Siloxane‐Based Building Units

Sonogashira cross-coupling of bromophenylethenyl-terminated cubic, double four-ring, siloxane cages with di-/triethynyl compounds results in microporous poly(ethynylene aryleneethenylene silsesquioxane) networks, simply termed as polyorganosiloxane networks (PSNs). In comparison with porous organic polymers reported previously, these PSNs show relatively high surface area and comparable thermal stability. Their apparent BET specific surface areas vary in the range of 850-1040 m(2) g(-1) depending on the length and the connectable sites of the ethynyl compounds. Analyses of pore size distribution revealed bimodal micropores with relatively narrow distribution. The degree of cross-linking affects the degree of cleavage of the siloxane bonds, and this suggests that partial cleavage of the siloxane cages is mainly a result of cage distortion. Hydrogen adsorption was performed to evaluate potential of the PSNs as hydrogen storage media. Uptakes of up to 1.19 wt% at 77 K and 760 Torr and initial isosteric heats of adsorption as high as 8.0 kJ mol(-1) were observed. These materials have been obtained by a combination of structural, synthetic organic, and materials chemistry, which can exploited to synthesize porous hybrid materials with specifically designed structures and functions.

Direct Hydrothermal Synthesis of Hierarchically Porous Siliceous Zeolite by Using Alkoxysilylated Nonionic Surfactant

A hierarchically porous siliceous MFI zeolite (silicalite-1) with narrow mesoporosity has been hydrothermally synthesized by using trialkoxysilylated alkyl poly(oxyethylene ether) as mesopore-directing agent. A mesostructured silica-surfactant composite was formed at the early stage of the reaction, and zeolite crystallization proceeded during subsequent hydrothermal treatment. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations of the crystallized products showed that micro- and mesopores were hierarchically assembled in unique particle morphology with rugged surfaces. Solid-state (29)Si and (13)C NMR revealed that the covalent bonds between the zeolite framework and mesopore-directing agent were present in the products before calcination. The use of nonsilylated alkyl poly(oxyethylene ether) or a silylated alkytrimethyl-ammonium-type cationic surfactant for the synthesis of silicalite-1 resulted in a mixture of mesoporous silica and zeolite as the final product, which suggests that the covalent interaction and nonelectrostatic charge matching interaction favor the formation of hierarchically mesoporous siliceous zeolite. This alkoxysilylated nonionic surfactant can also be extended to synthesize aluminosilicate MFI zeolite (ZSM-5).

Aragonite CaCO3 thin-film formation by cooperation of Mg2+ and organic polymer matrices

Aragonite thin films of calcium carbonate have been deposited on chitosan matrices by cooperation of chitosan, poly(aspartate) and MgCl2 in CaCO3 solution, and their double layered composite structures are obtained by the alternate operations of chitosan coating and thin-film crystallization.

Hybrid Nanoapatite by Polysaccharide Nanogel-templated Mineralization

Self-assembled nanogels of cholesterol-bearing mannan (CHM) containing phosphodiester bonds in its structure were used as templates for calcium phosphate mineralization to prepare novel organic—inorganic hybrid nanocarriers for drug-delivery systems. These hybrid materials were synthesized from a solution of calcium phosphate in the presence of CHM nanogels. The size and crystallinity of the nanomaterials were controlled by changing the calcium ion concentration. Spherical amorphous calcium phosphate (ACP) nanoparticles of ~20 nm in size and needle-shaped hydroxyapatite (HAp) crystals ~80 nm in length were formed from solutions of [Ca2+] = 0.8 and 2.0 mM, respectively. These hybrid nanomaterials showed excellent colloidal stability in solution, which was supported by the polymer chains of CHM on the outer surface of the hybrid nanomaterials. It was also found that an amorphous-to-crystalline transformation occurred during the formation of CHM nanogel-HAp hybrid nanomaterials.

One-Dimensional Assembly of Silica Nanospheres Mediated by Block Copolymer in Liquid Phase

Colloidal silica spheres and their assembly processes are encountered in nature and numerous technological applications. We report here a novel and facile method to prepare highly anisotropic one-dimensional (1D) arrays of silica nanospheres (SNSs) in the liquid phase. Uniform-sized SNSs ca. 15 nm in size assemble into a 1D chain-like structure in the presence of a commercially available block copolymer. The 1D assembly in the liquid phase is evident from Cryo-TEM observations and time-dependent turbidity measurement of the suspension. The mode of the assembly has been systematically controlled by the concentration of the block copolymer, pH of the suspension, and the concentration of a salt added to the system. These results suggest the importance of the balance between electrostatic repulsion and block copolymer-mediated attractive interaction that are operative between particles in the formation of 1D array.

Calcium carbonate/polymer composites: polymorph control for aragonite

Aragonite CaCO3/polymer thin film composites were successfully obtained by using cooperative effects of chitosan, poly(aspartate), and MgCl2. The structures of these composites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The combination of poly(aspartate) and the magnesium ion induced higher aragonite fractions in the thin films on the chitosan matrix, while the use of poly(acrylic acid) with Mg2+ gave lower aragonite fractions.

Generation of Surface-Bound Multicomponent Protein Gradients

Spatial control of bioactive ligands is achieved by integrating microfluidics and protein engineering. The proteins of interest are mixed in a gradient generator and immobilized on artificial polypeptide scaffolds through the strong association of heterodimeric ZE/ZR leucine zipper pairs. Protein densities and gradient shapes are easily controlled and varied in this method.

Preparation of anisotropic silica nanoparticles via controlled assembly of presynthesized spherical seeds.

A facile solution process for the preparation of anisotropic silica nanoparticles (ASNPs) is presented. ASNPs are prepared via controlled self-assembly of spherical silica seeds (22 nm) in alcohol-water mixed media, followed by their in situ fixation and overgrowth with tetraethoxysilane (TEOS). Ethanol and L-arginine (Arg) are used to modify the dielectric constant and ionic strength of the reaction media, by which seed assembly is controlled through the adjustment of electrostatic interaction. Ethanol and Arg also serve as a cosolvent and a catalyst for hydrolysis and condensation of TEOS, respectively, which enables us to produce ASNPs in a simple one-pot process. In addition to ASNPs with wormlike structures, different kinds of NPs (bimodal spherical NPs, monodisperse spherical NPs, and spherical aggregates) have also been obtained by changing the concentrations of ethanol and Arg. The length, thickness, or both of ASNPs are controlled systematically by varying the concentrations of Arg, seed NPs, and TEOS. Other alcoholic cosolvents, such as methanol, 1-propanol, 2-propanol, and t-butanol, are also effective to give ASNPs when the dielectric constant of the alcohol-water mixed media is properly adjusted, showing the versatility of the present method.