Preparation of composite particles with magnetic silica core and fluorescent polymer shell

Dual functions of magnetic and fluorescent properties were created in composite particles that incorporated magnetite (Fe₃O₄) nanoparticles in particle cores of silica and fluorescent pyrene in particle shells of polystyrene. The Fe₃O₄ nanoparticles were prepared with a conventional homogeneous precipitation method and surface modified with a coupling agent of carboxyethylsilanetriol. The silica particles incorporating Fe₃O₄ nanoparticles were synthesized with a modified Stöber method in which the Fe₃O₄ nanoparticles were added to a system of tetraethylorthosilicate (TEOS)/ammonia/water/ethanol. Then, the magnetite/silica composite particles were coated with the pyrene/polystyrene shell in a soap-free emulsion polymerization, which was conducted in the presence of pyrene in a mixed solvent of water/ethanol. The composite particles prepared in the mixed solvent had both magnetic and fluorescent properties. The fluorescent spectrum of the particles with Fe₃O₄ was very similar to that without Fe₃O₄, indicating that the magnetic component within the core particles scarcely interfered with the fluorescent emission from the polymer shell.     

Separation and optical resolution of a pair of atrop diastereomers of the octahedral rhodium(III) complex with a nine-membered S,S-chelate ring

Treatment of fac-[Rh(aet) 3] (aet = 2-aminoethanethiolate) with 2,2'-bis(bromomethyl)-1,1'-biphenyl gave a mononuclear rhodium(III) complex with a nine-membered S, S-chelate ring, fac-[Rh(aet)(L)] (2+) ([ 1] (2+), L = 2,2'-bis(2-aminoethylthiomethyl)-1,1'-biphenyl). Complex [ 1] (2+) afforded a pair of atrop diastereomers, Delta SS( S ax)/Lambda RR( R ax)-[ 1] (2+) ([ 1a] (2+)) and Delta SS( R ax)/Lambda RR( S ax)-[ 1] (2+) ([ 1b] (2+)), which involves the axial chirality ( R ax/ S ax) about a biphenyl moiety of L, besides the central chirality (Delta/Lambda) about a Rh (III) ion bound by two asymmetric ( R/ S) thioether donors. The atrop diastereomers ([ 1a] (2+) and [ 1b] (2+)) were successfully separated, isolated, and optically resolved, and the circular dichroism (CD) contribution from the axial chirality was evaluated by CD spectral analyses.     

Editorial for ADAC issue 3 of volume 15 (2021)

Advances in Data Analysis and Classification -     

Temperature-dependent carbon incorporation into the Si1−yCy film during gas-source molecular beam epitaxy using monomethylsilane

Coverage and adsorption state of hydrogen atoms on the growing surface of Si_1−yC_y film using monomethylsilane has been investigated by using temperature-programmed desorption (TPD) and multiple-internal-reflection Fourier-transform infrared spectroscopy (MIR-FT-IR). The surface hydrogen coverage decreases with the growth temperature T_g until it disappears at 800 °C. All the H₂-TPD spectra are well resolved into six SiH-related and one CH_n-related hydrogen desorption peaks. The SiH-related FT-IR peak showed a blue shift with increasing T_g, which, in conjunction with the TPD, is related to enhanced C incorporation at backbonds of SiH.     

ESR spectra and structure of the CF3Cl−, CF3Br−, and CF3I− radical anions

The anisotropic ESR spectra of the CF₃X^? radical anions (X = Cl, Br, I) have been observed following γ irradiation at 77 K of solid solutions containing up to 5 mole % of the CF₃X parent compound in tetramethylsilane (TMS), neopentane, and 2-methyltetrahydrofuran. The resolution of the line components in the TMS matrix allowed the spectra to be analyzed in detail, the parallel and perpendicular features showing clear evidence for axially symmetric hyperfine interactions with three equivalent fluorines and the unique halogen. On this basis, a matrix diagonalization program was used to calculate the line positions and the best-fit ESR parameters obtained. Confirmation of the CF₃X^? identification was achieved through chemical studies which showed that a similar ESR spectrum was generated by electron attachment to the parent molecule in a photoionization experiment. Also, the spectrum of the CF₃ radical was observed to grow in during the decay of the CF₃X^? spectrum in neopentane above 100 K. The spin density distributions calculated from the ESR parameters of these congeneric radical anions suggest that the unpaired electron resides in an a₁ (σ^*) antibonding orbital which is composed largely of the p orbitals from carbon and the unique halogen which lie along the C_3v symmetry axis of the radical anion. Consistent with this proposal, the spin densities in the s and p orbitals of the unique halogen increase along the series Cl, Br, I, which is the order expected for the effect of decreasing halogen electronegativity.     

Miscibility of poly(vinyl chloride) with chitin derivatives having poly(2-methyl-2-oxazoline) side chains

Binary blends of poly(vinyl chloride) (PVC) and chitin-graft-poly(2-methyl-2-oxazoline) showed miscibility in the blend fraction range of the latter lower than ca. 10 wt.-%. The glass transition temperature of PVC, which was determined by differential scanning calorimetry, changed to lower temperatures with increasing modified chitin contents up to 10 wt.-%. Segmental interaction between PVC and the graft copolymer was confirmed by the carbonyl stretching band shift in the FT-IR analysis.     

Chemical modification of hydroxyl groups of poly(vinyl alcohol) by a glycosidation reaction

A new procedure for chemical modification of poly(vinyl alcohol) (PVA) was established by a glycosidation reaction of hydroxyl groups in PVA with triacetylated sugar oxazoline 1 . ¹H and ¹³C NMR analyses indicated that triacetylated N‐acetyl‐D‐glucosamine (GlcNAc) was introduced onto a PVA backbone selectively via a β‐O‐glycoside linkage. Deacetylation of triacetylated GlcNAc‐substituted PVA 2 resulted in GlcNAc‐substituted PVA 3 in good yield. These modified PVAs 2 and 3 exhibited solubilities and thermal properties different from the original PVA.     

New chitin-based polymer hybrids, 1. Miscibility of poly(vinyl alcohol) with chitin derivatives

As a new class of biopolymer-based hybrid materials, the present paper describes the binary blends of a modified chitin and poly(vinyl alcohol) (PVA) which are miscible in the whole range of compositions. The blend films were prepared by the solvent cast method from a homogeneous aqueous solution of PVA and a chitin derivative having poly(2-methyl-2-oxazoline) side chains. Miscibility between PVA and poly(2-methyl-2-oxazoline) homopolymer was also revealed. Differential scanning calorimetry and FT-IR analyses were used to investigate the blends.