Production of Carbon Nanotube by Ethylene Decomposition over Silica-Coated Metal Catalysts

Formation of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) through the decomposition of ethylene at 973 K was achieved using various metal catalysts covered with silica layers. CNFs of various diameters were formed by ethylene decomposition over a Co metal catalyst supported on the outer surface of the silica. In contrast, silica-coated Co catalysts formed CNTs with uniform diameters by ethylene decomposition. Silica-coated Ni/SiO₂ and Pt/carbon black also formed CNTs with uniform diameters, while CNFs and CNTs with various diameters were formed over Ni/SiO₂ and Pt/carbon black without a silica coating. These results indicate that silica layers that envelop metal particles prevent sintering of the metal particles during ethylene decomposition. This results in the preferential formation of CNTs with a uniform diameter.     

Improvement of the surface quality of foam injection molded products from a material property perspective

Microcellular injection molding is an attractive method. However, their surface imperfections have been a major problem hindering wide industrial applications. Several methods have been proposed to improve the surface appearance of foams. In this study, we proposed a method to improve the surface appearance of polypropylene (PP) foams from the material property perspective, especially with regard to crystallization and viscosity. The basic idea of the surface improvement is to reduce the size of bubbles generated at the flow front, delay the solidification behavior of the polymer at the mold interface, squeeze the bubbles existing at the mold–polymer interface, and redissolve the bubbles into the polymer by holding pressure. Blending a low-modulus PP delays the crystallization of the polymers at the skin layer and solidification, taking enough time to squeeze the bubbles smaller. A sorbitol-based gelling agent, bis-O-([4 methylphenyl]methylene)-D-Glucitol, was used to increase the viscosity at a low strain rate to reduce the size of the bubbles generated at the flow front during the filling stage. The foam injection molding experiments demonstrated that the proposed method effectively improved the surface appearance of the foams. In particular, the surface appearance of the foams became almost equivalent to that of solid samples using low-modulus PP.     

Synthesis and optical properties of the [2.2]paracyclophane-containing π-conjugated polymer with a diacetylene unit

Summary Novel through-spaceπ-conjugated polymer based on poly(p-henyleneethynylene)/poly(p-phenylenebutadiynylene) hybrids containing a [2.2]paracyclophane unit in the main chain was synthesized by copper-catalyzed alkyne coupling reaction. The structure of the polymer was supported by ¹H NMR and IR spectra. The obtained polymer was soluble in common organic solvents such as THF, CH₂C1₂, CHC1₃ and toluene. The number-average of molecular weight of the polymer was estimated to be 63000 by GPC. The polymer emitted a bluish green light in solution and in the solid state. Received:24 September 2002/Revised version: 19 November 2002/Accepted: 19 November 2002 Correspondence to Yoshiki Chujo     

Synthesis and properties of conjugated copolymers having a tricarbonyl(arene)chromium and thiophene units in the main chain

Summary Palladium-catalyzed polymerization of η ⁶-(1,4-diethynylbenzene)tricarbonyl chromium (1) with 3-alkyl-2,5-dibromothiophene (2a-c) was carried out to give the corresponding alternating conjugated copolymers (5a-c) in good yields. The structures of the polymers were supported by ¹H NMR and IR spectra. The polymers obtained were soluble in common solvents such as THF, CH₂Cl₂, CHCl₃ and toluene. The molecular weights of the polymers were determined by GPC. Their thermal, optical and electrical properties were investigated in detail. Received: 18 March 2002 /Accepted: 1 April 2002     

Hydroboration copolymerization

Summary Organoboron copolymers were prepared by polyaddition of diene mixture or diene/diyne mixture, respectively, with thexylborane (1). When a mixture of dienes such as 1,2-diallyloxyethane (2a) and p-diallylbenzene (2b) was polymerized with 1, the peaks in GPC using both UV and RI detectors were shifted to higher molecular weight regions with the increase of the amount of 1. The molecular weight distribution of the copolymer obtained by this method indicated clear difference from that of a mixture of two homopolymers. On the other hand, when the poymerization between 1 and 1,7-octadiene (2c) was carried out in the presence of a trace amount of 1,7-octadiyne (4), the molecular weights of organoboron polymers were found to be increased when the ratio of 4/2c was increased.     

Synthesis and Properties of Novel Poly(p-phenylenevinylene)s Containing a Tricarbonyl(arene)chromium Unit in the Main Chain

Summary Novel π-conjugated polymers based on poly(p-phenylenevinylene)s (PPVs) containing a tricarbonyl(arene)chromium unit in the main chain were synthesized by Horner-Wadsworth-Emmons olefination. The structures of the polymers were supported by ^lH NMR and IR spectra. The polymers obtained were soluble in common solvents such as THF, CH₂Cl₂, CHCl₃ and toluene. The molecular weights of the polymers were determined by GPC. Their thermal, optical, and electrochemical properties were investigated in detail. Received: 18 November 2002/Revised version: 10 February 2003/ Accepted: 11 February 2003 Correspondence to Yoshiki Chujo     

Effects of aging on poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet radiation for gas separation

In this study, we investigated the effects of physical aging on the surface and gas‐transport properties of highly gas permeable poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet (VUV) radiation. VUV excimer lamp irradiation was performed on one side of the membrane for 6 or 60 min. The gas permeabilities for carbon dioxide (CO₂) and nitrogen (N₂) were determined through a volumetric measurement method at 23 °C. The gas permeabilities for CO₂ and N₂ increased temporarily at 7 days after 6 and 60 min of VUV irradiation of the membranes. The change in the gas permeability for N₂ was more remarkable than that for CO₂. These changes were related to the C?O or SiO_x ratio. The C?O ratio was related to the gas permeability of the membranes VUV‐irradiated for 6 min, whereas the SiO_x ratio was related to the gas permeability of the membranes VUV‐irradiated for 60 min. These changes affected the gas selectivities of the membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45973.     

CeO2–ZrO2 Solid Solution Catalyst for Selective Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide

CeO₂–ZrO₂ solid solution catalysts are very effective for the selective synthesis of dimethyl carbonate from methanol and CO₂. The activity was much dependent on the calcination temperature. The higher the calcination temperature, the higher the activity of the catalyst for DMC formation, though the BET surface area is lower on the catalyst calcined at higher temperature.     

Native state kinetic stabilization as a strategy to ameliorate protein misfolding diseases: a focus on the transthyretin amyloidoses

Small molecule-mediated protein stabilization inside or outside of the cell is a promising strategy to treat protein misfolding/misassembly diseases. Herein we focus on the transthyretin (TTR) amyloidoses and demonstrate that preferential ligand binding to and stabilization of the native state over the dissociative transition state raises the kinetic barrier of dissociation (rate-limiting for amyloidogenesis), slowing and in many cases preventing TTR amyloid fibril formation. Since T119M-TTR subunit incorporation into tetramers otherwise composed of disease-associated subunits also imparts kinetic stability on the tetramer and ameliorates amyloidosis in humans, it is likely that small molecule-mediated native state kinetic stabilization will also alleviate TTR amyloidoses.