Micelle formation of polystyrene-<Emphasis Type="Italic">block</Emphasis>-poly(4-<Emphasis Type="Italic">tert</Emphasis>-butoxystyrene) in hexane

A new type of hexane-soluble polymeric surfactant based on poly(4-tert-butoxystyrene) (P ^t BSt) was prepared by the nitroxide-mediated living radical polymerization, and their self-assemblies in hexane were explored. Polystyrene-block-P ^t BSt diblock copolymers with six different P ^t BSt block lengths were obtained by the sequential living radical polymerization of styrene followed by 4-tert-butoxystyrene using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator; Mn(P ^t BSt block) = 13,500, 21,700, 26,600, 47,500, 91,300, and 108,000 at the constant length of the PSt block (Mn = 12,900). Dynamic light-scattering studies demonstrated that the copolymers self-assembled into monodispersed spherical micelles in hexane. The hydrodynamic diameter of the micelles increased with an increase in the P ^t BSt block length. The micellar size also increased as the copolymer concentration increased. However, the size decreased as a result of the increasing temperature due to a decrease in the aggregation number. The ¹H NMR analysis confirmed that the copolymers formed micelles with PSt cores.     

Anisotropic Dissociation of π–π Stacking and Flipping‐Motion‐Induced Crystal Jumping in Alkylacridones and Their Dicyanomethylene Derivatives

Ethylacridone ( 1 b ) and dicyanomethylenated acridones 2 a , b , d showed crystal‐jumping activity upon heating. This is the first example of thermosalient behavior in a simple aromatic ketone and its derivatives. A systematic investigation of the jumping behavior of derivatives with different alkyl chains by variable‐temperature X‐ray crystal‐structure analyses revealed the mechanism of this phenomenon. Anisotropic dissociation of π stacking in a dimer was important for inducing crystal jumping in 1 b , whereas the collective fluctuation/flipping motion of a dicyanomethylene unit induced crystal jumping in 2 .     

Crystal structure of Eu-doped magnetoplumbite-type lanthanum aluminum oxynitride with emission site splitting

Eu-doped lanthanum aluminum oxynitride (LaAl₁₂(O,N)₁₉) with magnetoplumbite structure was prepared by nitridation of the oxide precursor obtained from aluminum glycine gel and subsequent post-annealing. Eu-doped lanthanum aluminum oxynitride exhibited blue light emission at 440 nm with a shoulder at 464 nm under excitation at 254 nm. Isostructural Eu-doped calcium aluminum oxide (CaAl₁₂O₁₉) exhibited a single emission peak at 415 nm. Structural refinement using neutron powder diffraction indicated that the lanthanum site occupied partially by Eu²⁺ splits into 2d and 6h sites in the aluminum oxynitride. The longer emission and the shoulder peak in the former aluminum oxynitride were observed in relation to the increasing covalency as well as crystal field splitting around doped Eu²⁺ induced by site splitting involved with the two kinds of anions.     

Effect of end groups of poly(n-butyl methacrylate) on its biocompatibility

Telechelic poly(n-butyl methacrylate)s (PBMAs) with various end groups were prepared using nonionic, anionic, cationic or zwitterionic azo-type radical initiators and cell adhesion onto the surfaces of the polymers was investigated. The tendency for cell adhesion to the polymers differed with and without pretreatment with phosphate-buffered saline (PBS, pH 7.4). The cell adhesion to polymer surfaces without pretreatment was lower than that with pretreatment. The effect of pretreatment with PBS was significant for PBMA with ionic end groups. Furthermore, cell adhesion to the surface of PBMA with zwitterionic end groups was suppressed compared with that to the surfaces of other polymers. It was presumed that positive and negative charges of zwitterionic groups in the same molecule negated each other at pH 7.4 and that the polymers with zwitterionic end groups had no effective charges. The results clearly indicated that biocompatibility of polymers can be changed by the introduction of functional groups at the ends of the polymer chains. Fabrication of functional material surfaces will be anticipated by the similar method in the future.     

Vapochromic Ionic Liquids from Metal–Chelate Complexes Exhibiting Reversible Changes in Color,Thermal, and Magnetic Properties

Vapor‐ and gas‐responsive ionic liquids (ILs) comprised of cationic metal‐chelate complexes and bis(trifluoromethanesulfonyl)imide (Tf₂N) have been prepared, namely, [Cu(acac)(BuMe₃en)][Tf₂N] ( 1 a ), [Cu(Bu‐acac)(BuMe₃en)][Tf₂N] ( 1 b ), [Cu(C₁₂‐acac)(Me₄en)][Tf₂N] ( 1 c ), [Cu(acac)(Me₄en)][Tf₂N] ( 1 d ), and [Ni(acac)(BuMe₃en)][Tf₂N] ( 2 a ) (acac=acetylacetonate, Bu‐acac=3‐butyl‐2,4‐pentanedionate, C₁₂‐acac=3‐dodecyl‐2,4‐pentanedionate, BuMe₃en=N‐butyl‐N,N′,N′‐tetramethylethylenediamine, and Me₄en=N,N,N′,N′‐trimethylethylenediamine). These ILs exhibited reversible changes in color, thermal properties, and magnetic properties in response to organic vapors and gases. The Cu^II‐containing ILs are purple and turn blue‐purple to green when exposed to organic vapors, such as acetonitrile, methanol, and DMSO, or ammonia gas. The color change is based on the coordination of the vapor molecules to the cation, and the resultant colors depend on the coordination strength (donor number, DN) of the vapor molecules. The vapor absorption caused changes in the melting points and viscosities, leading to alteration in the phase behaviors. The IL with a long alkyl chain ( 1 d ) transitioned from a purple solid to a brown liquid at its melting point. The Ni^II‐containing IL ( 2 a ) is a dark red diamagnetic liquid, which turned into a green paramagnetic liquid by absorbing vapors with high DN. Based on the equilibrium shift from four‐ to six‐coordinated species, the liquid exhibited thermochromism and temperature‐dependent magnetic susceptibility after absorbing methanol.     

MODIFICATION OF α-CHYMOTRYPSIN USING A WATER-SOLUBLE PHOTO-FENTON REAGENT

Abstract— -Modification of an enzyme, α-chymotrypsin, was examined by using a water-soluble photo-Fenton reagent. By photoirradiation of the enzyme with the reagent, which can occupy a binding site of the enzyme, a tryptophan residue in the vicinity of the active site was oxidized to N -formylkynurenine. Concurrently, the catalytic properties of the enzyme were largely changed: the K _m was increased and the k _catwas decreased. The decrease in k _cat for a specific amide substrate was the most significant among the esters and amides examined. The water-soluble photo-Fenton reagent would be useful to chemically modify relatively limited regions in biomolecules.     

Enhanced nucleophilicity of ambiphilic silylene and silylenoid bearing 8-(dimethylamino)-1-naphthyl group

Some new aspects of intramolecularly amine-coordinated silylenes, ammonium silaylide, and amine-coordinated magnesium (chloro)silylenoids are summarized. The divalent silicon species bearing the 8-(dimethylamino)-1-naphthyl group, generated by the thermal degradation of a pseudo-pentacoordinated ethoxy- or fluoro-disilane, behaves as a nucleophilic ammonium silaylide as well as the amine-coordinated silylene, whose electrophilic character is weakened in comparison with that of free silylenes in some reactions in the presence of trapping agents such as 1,3-diene, diphenyl acetylene (in the absence or presence of water), and phenylacetylene, and in the absence of any trapping agent. The amine-coordinated silylenoid also behaves as an ambiphile, but the reaction courses are different from those observed with the amine-coordinated silylene and silaylide. A novel amino-group migration from naphthyl carbon to silicon has been observed in both species.     

Positive Solutions to Second Order Singular Differential Equations Involving the One-Dimensional M-Laplace Operator

We consider a class of second order quasilinear differential equations with singular ninlinearities. Our main purpose is to investigate in detail the asymptotic behavior of their solutions defined on a positive half-line. The set of all possible positive solutions is classified into five types according to their asymptotic behavior near infinity, and sharp conditions are established for the existence of solutions belonging to each of the classified types.