Control of assembly size of poly (methacrylic acid)-grafted fullerenes in aqueous solution

We synthesized poly(methacrylic acid)-grafted fullerenes (PMA-C60) with different PMA molecular weights and investigated the assembly size formed by PMA-C60 in aqueous solution. The molecular weight of PMA strongly affects the assembly size: PMA-C60 with a larger molecular weight forms micelles with 20 nm diameters while PMA-C60 with a smaller molecular weight forms monodisperse assemblies with 200 nm hydrodynamic diameters. We succeeded in converting the large monodisperse assembly into micelles by adding either ionic species or ethanol. This result provides insight into controlling the assembly size of fullerene-containing assemblies

PVP-Grafted Fullerenes in Aqueous Solution

Poly(N-vinylpyrrolidone) (PVP)-grafted fullerenes (PVP-C60 and PVP-C70) were synthesized by iniferter polymerization in order to fabricate water-soluble fullerene containing micelles. PVP-C60 formed micelles with hydrodynamic diameters ranging from 15 to 33 nm. The solubilization of fullerene molecules into the core of the PVP-C60 micelles was also found to control the size of the micelles. By increasing the amount of added fullerene, we gradually increased the micelle size before drastically increasing it to that of 200 nm in hydrodynamic diameter. The drastic change occurred at a critical value of the added C60/PVP monomer ratio, almost independently of the molecular weight of PVP

Tuning Polymer-Grafted Particle Monolayer Structure at the Air-Water Interface by Introducing Anisotropic Features

Fabrication of anisotropic material is one of the important topics and we examined to introduce “anisotropic” nature by spreading polymer-grafted particle on the medium with polymer-reactive potential. Poly (tert-butyl methacrylate) (PtBMA) was polymerized from polystyrene latex (PSL) surface by ATRP to give PtBMA-grafted PSL (PSL-PtBMA). Particle monolayer was formed at air-water and air-acidic water interfaces and the monolayer characteristics were compared by π-A isotherm measurements, SEM observations, and contact angle measurements. π-A isotherms, in particular, indicates that the interaction between polymer chains become stronger by changing the subphase condition, which suggests that anisotropicparticle monolayer formation

Electric-Alignment Immobilization of Liquid Crystalline Colloidal Nanosheets with the Aid of a Natural Organic Polymer

Inorganic nanosheets obtained by exfoliation of a layered crystal in water form colloidal liquid crystals, and their alignment can be controlled by an electric field. In order to realize the immobilization of the electrically aligned niobate nanosheets without external forces, an aqueous gelator, agar, is introduced to the niobate nanosheet system to utilize the thermosensitive sol–gel transition property of agar. Alignment of nanosheets in a niobate–agar system is performed by applying an electric field above the sol–gel transition temperature, and then, the sample is cooled down, followed by cooling below the transition temperature with the electric field turned off. The aligned structure is kept for more than 24 h after the removal of the electric field. The concentration of agar is a key parameter for both the orientation of nanosheets and the retention of the orientation

Development of Structural Color by Niobate Nanosheet Colloids

Inorganic nanosheets obtained by exfoliation of layered crystals of hexaniobate in water form colloidal liquid crystals. We found that they develop various structural colors by moderating nanosheet concentration and ionic atmosphere

Preparation of Cellulose Nanocrystals based Core-Shell Particles with Tunable Component Location

We report a versatile method for preparing a particulate composite based on cellulose nanocrystals (CNCs) and polyethylene glycol (PEG) via a self-organized precipitation method. The particulate composite had a core–shell structure, and depending on the molecular weight of the PEG, two types of particulates could form: one with CNCs as the core and the other with CNCs as the shell

Photoinduced electron transfer in semiconductor–clay binary nanosheet colloids controlled by clay particles as a turnout switch

Although semiconductor photocatalysis has been investigated actively for a long time, control of dark processes successive to electron transfer from photocatalysts is almost unexplored compared with designing photocatalysts themselves. The present study proposes employment of clay particles as for controlling the dark processes independently of semiconductor photocatalyst particles. We employed niobate–clay binary nanosheet colloids, where colloidal niobate and clay nanosheets are spatially separated at a micrometer level. Niobate nanosheets worked as the semiconductor photocatalyst that released electrons upon UV excitation, and clay nanosheets worked as the turnout switch of the released electrons to determine their destination. When methylviologen (MV2+) molecules that accept the electrons released from niobate were adsorbed on clay nanosheets, reduction of MV2+ predominantly occurred, and hydrogen was little evolved from the colloid. When Pt nanoparticles were deposited on clay nanosheets, photocatalytic hydrogen evolution occurred because Pt loaded on the clay nanoparticles played a role of cocatalyst. When MV2+ and Pt were co-loaded on clay nanosheets, both of MV2+ reduction and hydrogen evolution occurred competitively. The photocatalytic hydrogen evolution carried out by stirring the colloid sample was worse than that conducted without stirring, which indicated positive contribution of the spatial separation of photocatalytic niobate and cocatalytic clay nanosheets

Mesoscopic Architectures Made of Electrically Charged Binary Colloidal Nanosheets in Aqueous System

Inorganic layered materials can be converted to colloidal liquid crystals through exfoliation into inorganic nanosheets, and binary nanosheet colloids exhibit rich phase behavior characterized by multiphase coexistence. In particular, niobate–clay binary nanosheet colloids are characterized by phase separation at a mesoscopic (∼several tens of micrometers) scale whereas they are apparently homogeneous at a macroscopic scale. Although the mesoscopic structure of the niobate–clay binary colloid is advantageous to realize unusual photochemical functions, the structure itself has not been clearly demonstrated in real space. The present study investigated the structure of niobate–clay binary nanosheet colloids in detail. Four clay nanosheets (hectorite, saponite, fluorohectorite, and tetrasilisic mica) with different lateral sizes were compared. Small-angle X-ray scattering (SAXS) indicated lamellar ordering of niobate nanosheets in the binary colloid. The basal spacing of the lamellar phase was reduced by increasing the concentration of clay nanosheets, indicating the compression of the liquid crystalline niobate phase by the isotropic clay phase. Scattering and fluorescence microscope observations using confocal laser scanning microscopy (CLSM) demonstrated the phase separation of niobate and clay nanosheets in real space. Niobate nanosheets assembled into domains of several tens of micrometers whereas clay nanosheets were located in voids between the niobate domains. The results clearly confirmed the spatial separation of two nanosheets and the phase separation at a mesoscopic scale. Distribution of clay nanosheets is dependent on the employed clay nanosheets; the nanosheets with large lateral length are more localized or assembled. This is in harmony with larger basal spacings of niobate lamellar phase for large clay particles. Although three-dimensional compression of the niobate phase by the coexisting clay phase was observed at low clay concentrations, the basal spacing of niobate phase was almost constant irrespective of niobate concentrations at high clay concentrations, which was ascribed to competition of compression by clay phase and restoring of the niobate phase

Xセン オヨビ チュウセイシ ハンシャリツホウ ニ ヨル キエキ カイメン ニ ケイセイシタ イオンセイ リョウシンバイセイ コウブンシ タンブンシマク ノ ナノ コウゾウ ニ カンスル ケンキュウ

京都大学0048新制・課程博士博士(工学)甲第10543号工博第2337号新制||工||1300(附属図書館)UT51-2004-C95京都大学大学院工学研究科高分子化学専攻(主査)教授 澤本 光男, 教授 福田 猛, 教授 木村 俊作学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA