Controlled polymerization of epoxides: Metal‐free ring‐opening polymerization of glycidyl phenyl ether initiated by tetra‐n‐butylammonium fluoride in the presence of protic compounds

Metal‐free controlled ring‐opening polymerization of glycidyl phenyl ether (GPE) was achieved using tetra‐n‐butylammonium fluoride (Bu₄NF) as an initiator in the presence of water and ethanol as chain transfer agents (CTAs). Number‐averaged molecular weight of poly(GPE) increased with an increase of [GPE]₀/([Bu₄NF]₀ + [CTA]₀) values, showing relatively narrow molecular weight distributions. NMR spectroscopic analysis exhibited a formation of ethoxy groups as well as FCH₂ at the initiating polymer chain‐end when ethanol was used as the CTA in the polymerization. These results indicate that Bu₄NF acts as a catalyst as well as the initiator for this polymerization system. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

NIR spectroscopic study of the dissolution process in pharmaceutical tablets

In this study, water penetration and the interaction between water and a pharmaceutical excipient in a tablet were investigated using near-infrared (NIR) spectroscopy and perturbation-correlation moving-window two-dimensional correlation spectroscopy (PCMW-2DCS). The penetration rate of water into a tablet was mainly dependent on the porosity of the tablet and was less dependent on the type of excipient. This behavior was well described by the Lucas–Washburn theory. The PCMW-2DCS technique revealed that there are two-staged interaction changes in NIR spectra of the water–powder interactions. The first and second changes corresponded to the water–solid interaction and the dissolution of the solid, respectively. The diffusion-controlled dissolution model by Nernst well explained these results.     

Growth of GaN single crystals with extremely low dislocation density by two-step dislocation reduction

We have discovered a mechanism which can significantly reduce the dislocation density during the growth of GaN single crystals in the Na flux method. The significant reduction of the dislocation density occurs in the later stage of LPE growth, rather than solely at the seed-LPE interface for which we have already reported evidence indicating the presence of bundling dislocations. The two-step dislocation reduction is the key in achieving extremely low dislocation density using this method.     

One-step synthesis of hierarchical porous γ-alumina with high surface area

Hierarchical porous γ-alumina is successfully fabricated from a precursor solution consisting of surfactants, polystyrene (PS) spheres, inorganic salts and solvents. After calcinations, uniform macropores are closely packed. The macropore size coincides with the original PS sphere size. These macropores are connected by small windows. In addition, the macropore walls have mesoporous structures, as confirmed by SAXS measurement and TEM observation. After calcination at 900 °C, the amorphous alumina frameworks are converted to the crystallized γ-alumina phase. Even after crystallization, the existence of uniform mesopores and high surface are well retained, though the mesoporous ordering is lower.     

Surface structures and osteoblast response of hydrothermally produced CaTiO3 thin film on Ti-13Nb-13Zr alloy

This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti-13Nb-13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO₃ layer. Post heat-treatment at 400 °C for 2 h in air significantly decreased water contact angles in the CaTiO₃ layer (p < 0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces (p < 0.001), and also an upregulated expression of various integrin genes (α1, α2, α5, αv, β1 and β3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti-13Nb-13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti-13Nb-13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.