Kazuko Fujii

Synthesis of ion-exchangeable layered polysiloxane by sol–gel reaction of aminoalkyltrialkoxysilane: a new preparation method for layered polysiloxane materials

An ion-exchangeable layered polysiloxane containing alkylammonium groups was synthesized by sol–gel reaction of 3-aminopropyltrimethoxysilane (APTMOS) catalyzed by hydrochloric acid; the present reaction system provides a new method for the preparation of layered polysiloxane materials.

Compositional gap in dioctahedral-trioctahedral smectite system; beidellite-saponite pseudo-binary join

A series of hydrothermal experiments were performed to determine the phase relations on the beidellite-saponite pseudo-binary join. Quenched glasses with stoichiometric dehydrated compositions of an Na-rich smectite on the join were heated at 250–500°C for durations of 1–151 d at 100 MPa. Time-temperature diagrams showed that immiscibility occurs between dioctahedral smectite (beidellite) and trioctahedral smectite (saponite) below 400°C. Thus, smectite with intermediate chemical composition was considered as metastable in this system. Above 400°C the assemblage of regularly interstratified saponite-chlorite, quartz, and feldspar was recognized in the intermediate chemical compositional region of this join. On the beidellite side of this join, beidellite and mixed-layer phases of smectite and a regular interstratification of montmorillonite-beidellite, are possible phases that occur at <300°C. They readily reacted to form a mixture of dioctahedral rectorite plus quartz at 300°C. This assemblage then reacted to a dioctahedral “mica”, which can expand with glycol and quartz. On the saponite side of this join, a single phase, saponite, existed at <400°C, and transformed to saponite plus trioctahedral rectorite with aging and increasing temperature of synthesis. The alteration was affected strongly by the chemical composition of the binary system.

Reversibly meltable layered alkylsiloxanes with melting points controllable by alkyl chain lengths

Meltable layered alkylsiloxanes (CnLSiloxanes) were synthesized from tetraethoxysilane and alkyltrialkoxysilanes with carbon numbers (n) of 12, 16, and 18 via hydrolysis and polycondensation at 100 and 150 °C under basic conditions. Differential scanning calorimetric (DSC) measurements revealed that CnLSiloxanes melted reversibly at −0.8 to 51.3 °C, the melting points being dependent on n. Scanning electron microscope (SEM) images showed that thin plates were stacked. X-ray diffraction (XRD) peaks were observed at angles corresponding to distances (d) of 2.1, 2.5, and 2.8 nm for C12-, C16-, and C18LSiloxanes, respectively. High-resolution solid-state 13C nuclear magnetic resonance (NMR) measurements showed that the organic moieties were alkylsilyl groups with long alkyl chains and that an all-trans conformation was dominant. This was supported by the XRD peak corresponding to a d value of 0.41 nm. High-resolution solid-state 29Si NMR measurements demonstrated the presence of SiO4 and CSiO3 units. A structural model has been proposed for CnLSiloxanes, where siloxane sheets consisting of the SiO4 and CSiO3 units are stacked with the ordered interdigitated monolayer of the alkyl chains in between and are bonded covalently with the alkyl chains.

Adsorption of amino acids by fullerenes and fullerene nanowhiskers

Abstract We have investigated the adsorption of some amino acids and an oligopeptide by fullerene (C60) and fullerene nanowhiskers (FNWs). C60 and FNWs hardly adsorbed amino acids. Most of the amino acids used have a hydrophobic side chain. Ala and Val, with an alkyl chain, were not adsorbed by the C60 or FNWs. Trp, Phe and Pro, with a cyclic structure, were not adsorbed by them either. The aromatic group of C60 did not interact with the side chain. The carboxyl or amino group, with the frame structure of an amino acid, has a positive or negative charge in solution. It is likely that the C60 and FNWs would not prefer the charged carboxyl or amino group. Tri-Ala was adsorbed slightly by the C60 and FNWs. The carboxyl or amino group is not close to the center of the methyl group of Tri-Ala. One of the methyl groups in Tri-Ala would interact with the aromatic structure of the C60 and FNWs. We compared our results with the theoretical interaction of 20 bio-amino acids with C60. The theoretical simulations showed the bonding distance between C60 and an amino acid and the dissociation energy. The dissociation energy was shown to increase in the order, Val < Phe < Pro < Asp < Ala < Trp < Tyr < Arg < Leu. However, the simulation was not consistent with our experimental results. The adsorption of albumin (a protein) by C60 showed the effect on the side chains of Try and Trp. The structure of albumin was changed a little by C60. In our study Try and Tyr were hardly adsorbed by C60 and FNWs. These amino acids did not show a different adsorption behavior compared with other amino acids. The adsorptive behavior of mono-amino acids might be different from that of polypeptides.