High physisorption affinity of water molecules to the hydroxylated aluminum oxide (001) surface

The adsorption mechanism of water on the hydroxylated (001) plane of α-Al(2)O(3) was studied by measuring adsorption isotherms and GCMC simulations. The experimental adsorption isotherms for three α-Al(2)O(3) samples from different sources are typical type II, in which adsorption starts sharply at low pressures, suggesting a high affinity of water to the Al(2)O(3) surface. Water molecules are adsorbed in two registered forms (bilayer structure). In the first form, water is registered at the center of three surface hydroxyl groups by directing a proton of the water. In the second form, a water molecule is adsorbed by bridging two of the first-layer water molecules through hydrogen bonding, by which a hexagonal ring network is constructed over the hydroxylated surface. The network domains are spread over the surface, and their size decreases as the temperature increases. The simulated adsorption isotherms present a characteristic two-dimensional (2D) phase diagram including a 2D critical point at 365K, which is higher than that on the hydroxylated Cr(2)O(3) surface (319 K). This fact substantiates the high affinity of water molecules to the α-Al(2)O(3) surfaces, which enhances the adsorbability originating from higher heat of adsorption. The higher affinity of water molecules to the α-Al(2)O(3) (001) plane is ascribed to the high compatibility of the crystal plane to form a hexagonal ring network of (001) plane of ice Ih.     

Scanning force microscopic study of protein adsorption on the surface of organosilane monolayers prepared by the Langmuir‐Blodgett method

The n‐octadecyltrichlorosilane (OTS, CH₃(CH₂)₁₇SiCl₃), 18‐nonadecenyltrichlorosilane (NTS, CH₂=CH(CH₂)₁₇SiCl₃), [2‐(perfluorooctyl)ethyl] trichlorosilane (FOETS, CF₃(CF₂)₇CH₂CH₂SiCl₃) monolayers, and their mixed monolayers were used as the model substrates for the study of protein adsorption mechanism. Surface plasmon resonance (SPR) spectroscopy was applied to analyze the protein adsorption behavior onto the surface of the monolayers. Atomic force microscope (AFM) was used to observe the monolayer surfaces after exposure of these monolayers to bovine serum albumin (BSA) and γ‐globulin(IgG) solution. AFM observation revealed that the charged protein either below or above the isoelectric point was preferentially adsorbed onto the FOETS phase of the (OTS/FOETS) mixed monolayer. SPR revealed that the amount of adsorbed protein in the charged state was lower than that in the neutral state. These results indicate that the preferential adsorption of protein onto the FOETS phase for the mixed monolayer systems at either below or above pI is due to (1) the minimization of interfacial free energy between the monolayer surface and the buffer solution, and (2) the electrostatic repulsion among protein molecules bearing charges.     

Extended Hartree-Fock (EHF) theory of chemical reactions

The triplet-instability analysis of the closed-shell RHF solutions has been carried out in relation to the orbital and spin correlation effects for various transition structures (TS) and reaction intermediates. It is found that the RHF solutions even for cyclic transition states of the Woodward-Hoffmann symmetry-allowed reactions often involve the triplet instability, indicating the crucial role of correlation corrections. The di- and tetra-radical characters for the transition structures are calculated by the projected UHF (PUHF) solutions resulting from the instability. The spin projection is also crucial for the UHF Møller-Plesset (UMP) correlated wavefunctions obtained for the transition structures of 1,3-dipolar, Diels-Alder, ene and related reactions. The relative stability between cyclic and acyclic TS for these reactions is examined at the approximately projected UHF MP2 (APU MP2) level. The former is found to be more favorable than the latter if the correlation correction is taken into account for TS in a well-balanced manner.Dedicated to Professor J. Koutecký on the occassion of his 65th birthday     

Vis‐sensitive photopolymer containing vinyl ether compound and pyrromethene dye

A visible light(vis)‐sensitive photoresist based on the concept of chemical amplification was developed utilizing poly(p‐hydroxystyrene) (PHS), 2,2‐bis[4‐(2‐(vinyloxy)‐ethoxy)phenyl]propane (BPA‐DEVE) as a crosslinking agent, N‐trifluoromethylsulfonyloxy‐1,8‐naphthalimide (NIT) as a photoacid generator (PAG) and pyrromethene dyes such as 1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRH) and 2,8‐diethyl‐1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRE) and 3,3′‐carbonylbis(7,7′‐diethylaminocoumarin) (KCD). On irradiation with an argon ion laser, the photopolymer comprising PRH and PRE exhibited a high sensitivity of 65 and 46 mJ cm^?2, respectively. It is suggested that the sensitization mechanism of the pyrromethene dye/PAG system involves singlet electron transfer. The sensitivity of the photoresist increased with the decreasing molecular weight of PHS because of the high dissolution rate. Copyright © 2002 John Wiley & Sons, Ltd.     

Surface patterned graft copolymerization of hydrophilic monomers onto hydrophobic polymer film upon UV irradiation

A random copolymer [p(MMA/DMAB)] composed of methyl methacrylate (MMA) and 2,2‐dimethoxy‐1,2‐di(4‐methacryloyloxy)phenylethane‐1‐one (DMAB), which can simultaneously act as a photoradical initiator and crosslinkable monomer, was prepared by free radical random copolymerization. A hydrophobic film on quartz glass was prepared using p(MMA/DMAB) by a spin‐coating technique. Hydrophilic methacrylic acid (MA) and 2‐methacryloyloxyethyl phosphorylcholine (MPC) were graft‐copolymerized from the hydrophobic p(MMA/DMAB) film in water by photo‐cleavage of the DMAB unit. The graft copolymer of MA and MPC was characterized by infrared and X‐ray photoelectron spectroscopies and contact angle measurements. To confirm that MPC can be grafted onto the surface of the film selectively at only UV‐irradiated sites, photoinduced graft copolymerization of MPC using a photomask was performed to prepare a pMPC patterned p(MMA/DMAB) film. The film was stained using a rhodamine 6G dye that can absorb specifically to pMPC to confirm the pMPC pattern. The p(MMA/DMAB) film can be applied to various fields including photolithography and biomedical applications, because the film surface properties can be controlled using various vinyl monomers selectively on UV‐irradiated sites. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2822–2829     

Super-liquid-repellent surfaces prepared by colloidal silica nanoparticles covered with fluoroalkyl groups

A simple and easy method to prepare super-liquid-repellent surfaces is proposed. Sol-gel films were prepared by hydrolysis and condensation of alkoxysilane compounds. Both surface energy and roughness were controlled using colloidal silica particles and fluoroalkylsilane. When the fractional amounts of both colloidal silica and fluoroalkylsilane were optimized in the films, the film surface exhibited repellency to both water and oil. Finally, it was shown that the method proposed here would be applied to a simple one-pot coating for a uniform large area, and be useful for practical use.     

Effect of molecular weight on microcrystalline structure formation in polymer with perylenediimide side chain

The effect of molecular weight on the molecular aggregation structure of polymers bearing a pendant perylenediimide (PDI) side chain, designated PAc12PDI, was investigated using synchrotron radiation X‐ray diffraction measurements. It was found that depending on molecular weight, either the main chain axis or the side chain axis behaves as the longitudinal axis in fiber samples and was aligned parallel to the fiber axis. A similar phenomenon is present in thin film samples, but was complicated by the additional influence of the interfacial free energy of the side chain group. Even in the case of the polymer with lower molecular weight, the face plane of PDI was found to show both parallel and perpendicular orientations to the substrate (i.e., flat‐on and edge‐on orientations). On the other hand, if the length of the main chain is sufficiently long with respect to the length of the side chain, the face plane of PDI was oriented perpendicular to the substrate, leading to an edge‐on orientation in the thin film. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2275–2283     

Fischer-Tropsch synthesis over Ru/Al2O3 catalysts

Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al₂O₃ catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature, synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al₂O₃ was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction.     

Surface and interfacial segregation in blends of polystyrene with functional end groups and deuterated polystyrene

The effect of chain-end chemistry on surface and interfacial segregation in symmetric blends of polystyrene (hPS)/deuterated polystyrene (dPS) has been investigated by X-ray photoelectron and secondary ion mass spectroscopy in conjunction with neutron reflectivity measurements. Alpha,omega-fluoroalkyl- and alpha,omega-carboxy-terminated polystyrenes (alpha,omega-hPS(Rf)2 and alpha,omega-hPS(COOH)2) were used as end-functionalized polymers; the former possesses chain ends with lower surface energies, and the latter possesses higher surface energies compared with that of the main chain. In the case of an alpha,omega-hPS(Rf)2/dPS blend film, alpha,omega-hPS(Rf)2 was enriched at the surface owing to the surface localization of the Rf groups, although the surface energy of the hPS segments was slightly higher than that of the dPS ones. On the contrary, in the case of an alpha,omega-hPS(COOH)2/dPS blend film, dPS was preferentially segregated at the surface. This may be due to a surface depletion of COOH ends and an apparent molecular weight increase of alpha,omega-hPS(COOH)2 produced by a hydrogen-bonded intermolecular association of COOH ends in addition to the surface energy difference between hPS and dPS segments. Interestingly, both Rf and COOH chain ends were partitioned to the substrate interface for the alpha,omega-hPS(Rf)2/dPS and alpha,omega-hPS(COOH)2/dPS blend films, resulting in the segregation of the hPS component at the substrate interface for both blends. The results presented imply that surface and interfacial segregation in polymer blends could be regulated by incorporating functional groups into the end portions of one component.