Toshihiko Arita

Abstract Summary: Application of high pressure, up to 2 500 bar, in cumyl dithiobenzoate‐mediated styrene reversible addition fragmentation chain transfer (RAFT) polymerizations was found to be extremely advantageous with respect to both rate and control of polymerization. The overall rate of polymerization could be increased by a factor of approximately 3 with, e.g., at 23% conversion, concomitantly reducing the polydispersity indices from 1.35 to 1.10. No significant effect of increased pressu

Self-initiated reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene at temperatures of 120, 150, and 180 °C, using cumyl dithiobenzoate (CDB) at concentrations between 5.0 × 10-3 and 2.0 × 10-2 mol L-1 as the RAFT agent were performed at 1000 bar. The increase of average molecular weight with monomer conversion, the shape of the molecular weight distributions, and polydispersity indices below 1.5 at monomer conversions up to about 50% indicate control of styrene bul

Abstract Summary: Reversible addition fragmentation chain transfer (RAFT) polymerizations of methyl acrylate (MA) in solution containing either 22 vol.‐% CO 2 or toluene were performed at 80 °C and 300 bar using cumyl dithiobenzoate (CDB) at concentrations between 1.8 × 10 −3 to 2.5 × 10 −2 mol · L −1 as the RAFT agent. Product molecular weight distributions and average molecular weights indicated the successful control of MA polymerization in CO 2 , even at low CDB concentrations. RAFT polymeri

Ceria (CeO2) nanocyrstals which could be transparently dispersed in several organic solvents were synthesized by organic-ligand-assisted hydrothermal synthesis. We have studied the dispersity of the nanocrystals into typical organic solvents using dynamic light scattering (DLS) measurement. The mean diameter of the dispersant (the nanocrystals’ cluster) varied with changing the solvent species. When the solubility parameter (SP) values of the solvent and the modifier were comparable to each othe

Microspheric Janus particles with maghemite nanoparticles (NPs) in the hemisphere were investigated. Poly(styrene) (PS)-grafted maghemite NPs were embedded into the PS phase of a PS–poly(isoprene) (PI) Janus polymer particle prepared by a Self-organized Precipitation (SORP) method. The obtained Janus particles showed magnetic field responsive drifts and rotation in water. Potential application in electric paper pixels can be expected from the anisotropic magnetic response of the particle.

We have found that the concentrated poly(methyl methacrylate) (PMMA) brush showed the very good nanoparticles (NPs) repellency in its good solvent, e.g. tetrahydrofuran (THF). Whereas the oil- and hydro-phobic (fluorinated), hydrophobic and hydrophilic surfaces adsorbed a lot of NPs. The repellency of NPs did not depend on the surface nature of the NPs. Preparing absorption free columns for size exclusion chromatography (SEC) may enable us to separate quantum dots (QDs) and NPs according to thei

Colloidal CeO2 nanoparticles (HNPs) stabilized with a decanoic fatty acid self-assembled monolayer (SAM) (decHNPs) showed very good dispersibility, i.e., perfect dispersion in cyclohexane up to 20 wt%. However, the HNPs stabilized with a dodecanoic acid SAM (dodHNPs) did not show good dispersion, i.e., at most 0.2 wt%. Interestingly, when we mixed equal portions of 5 wt% decHNPs in cyclohexane and 2 wt% dodHNPs in cyclohexane, the mixture showed much better dispersion than 1 wt% of dodHNPs in cy

Titanium dioxide (TiO2, anatase) nanocyrstals tha can be transparently (perfectly) dispersed in several organic solvents were synthesized by organic-ligand-assisted hydrothermal synthesis. To analyze the dispersion behavior of surface-modified nanocrystals from the surface of the surface-modified nanocrystals, three types of surface-modified TiO2 nanocrystals were prepared. Depending on the surface nature of the surface-modified TiO2 nanocrystals, the nanocrystals showed different dispersion beh

The solution-state property of three-dimensional self-assembled monolayers (3D SAMs) on CeO2 nanoparticles (NPs) has been found to seriously affect dispersion of the NPs. The chain length and solvent-dependent changes in the properties of SAMs were investigated by using various n-alkanoic acid SAMs on CeO2 NPs and various nonpolar organic solvents. NMR and DSC were employed to analyze solution-state behavior of the 3D SAMs. A scaling approach on the chain length and the grafting density of the S

We report experimental verification of the Smoluchowski theory for diffusion-controlled reactions in solution at the steady-state limit. We have determined both the diffusion coefficients and the self-termination reaction rates of the diphenylmethyl radical simultaneously. Smoluchowski theory is insufficient to discuss the reaction rate for the self-termination reaction of the diphenylmethyl radical, so the reaction rate of an encounter complex based on the Collins-Kimball treatment is estimated

Abstract Self-assembled monolayers (SAMs) of decanoic acids were prepared on CeO2 nanoparticles (NPs). The dispersion of the NPs was improved by increasing the packing density of decanoic acid SAM on CeO2 NPs. According to our proposed criterion related to the SAM on NPs for stable dispersion in nonpolar liquids, the CeO2 NPs were dispersed up to 77 wt % and perfectly dispersed up to 50 wt % in cyclohexane.