Interaction of naphthalene‐labeled poly(hydrochloride quaternized 2‐norbornene‐5‐methyleneamine) with O/W microemulsion droplets

Interaction between naphthalene‐labeled poly(hydrochloride quaternized 2‐norbornene‐5‐methyleneamine), poly(HCQNBMA)/NA (luminophore), and quencher, emulsifier or coemulsifier in the aqueous or microemulsion media was studied by using steady‐state fluorescence measurements. Fluorescence experiments were carried out with poly(HCQNBMA)/NA dissolved in the aqueous solutions of ionic and nonionic emulsifiers, emulsifier/n‐hexane/water microemulsion (A) and emulsifier/n‐hexane/1‐pentanol/water microemulsion (B), respectively. The intensity of fluorescence emission of poly(HCQNBMA)/NA was much higher in the aqueous phase than in microemulsion. Furthermore, the aqueous solution of ionic emulsifier increased the monomer emission. The increase in the monomer emission can be ascribed to the shielding of the naphthalene (NA) groups by SDS micelles. This separates NA groups from each other, which depresses the deactivation of excited states. The strong decrease in monomer emission within the microemulsion media probably results from the elongated conformation structure of the polymer molecule, and higher conformation freedom of NA groups, which increases interaction between the probe and the quencher. The formation of nonfluorescence clusters is not ruled out. The quenching of NA emission by nitromethan (NM) is much stronger in microemulsion than in the aqueous phase, and the quenching is more pronounced for the low molecular weight 2‐norbornene‐5‐methoxylnaphthalene (NBMNA) than for its polymer. The extent of penetration of reactants into the interfacial layer governs quenching of hydrophobic NA probe by hydrophilic quencher. Furthermore, the quenching events are connected with the thickness and density of the interfacial layer, as well as its charge. The addition of coemulsifier (1‐pentanol) increases the total surface area of the microdroplets, the entry rate of reactants into the microdroplets, and the interaction of hydrophobic and hydrophilic reactants. The quenching events are more pronounced in the close packed o/w interfacial layer than in the loosely packed one. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 101–114, 2001     

Synthesis and characterization of novel polyamide‐imides containing noncoplanar 2,2′‐dimethyl‐4,4′‐biphenylene unit

A new diimide‐dicarboxylic acid, 2,2′‐dimethyl‐4,4′‐bis(4‐trimellitimidophenoxy)biphenyl (DBTPB), containing a noncoplanar 2,2′‐dimethyl‐4,4′‐biphenylene unit was synthesized by the condensation reaction of 2,2′‐dimethyl‐4,4′‐bis(4‐minophenoxy)biphenyl (DBAPB) with trimellitic anhydride in glacial acetic acid. A series of new polyamide‐imides were prepared by direct polycondensation of DBAPB and various aromatic diamines in N‐methyl‐2‐pyrrolidinone (NMP), using triphenyl phosphite and pyridine as condensing agents. The polymers were produced with high yield and moderate to high inherent viscosities of 0.86–1.33 dL · g⁻¹. Wide‐angle X‐ray diffractograms revealed that the polymers were amorphous. Most of the polymers exhibited good solubility and could be readily dissolved in various solvents such as NMP, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), dimethyl sulfoxide, pyridine, cyclohexanone, and tetrahydrofuran. These polyamide‐imides had glass‐transition temperatures between 224–302 °C and 10% weight loss temperatures in the range of 501–563 °C in nitrogen atmosphere. The tough polymer films, obtained by casting from DMAc solution, had a tensile strength range of 93–115 MPa and a tensile modulus range of 2.0–2.3 GPa. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 63–70, 2001     

Conjugated vinyl derivatives of chitooligosaccharide: Synthesis and characterization

The introduction of a conjugated vinyl group to chitooligosaccharide (COS) has been easily accomplished by the coupling of glycidyl methacrylate (GMA) to COS in aqueous solution without an additional catalyst. Depolymerization of chitosan was carried out by deaminative cleavage using sodium nitrite. The average degree of polymerization of COS could be controlled by varying the molar ratio of sodium nitrite and the amino group of chitosan. The degree of substitution (percentage), as determined by ¹H NMR, of GMA to COS increased up to 60% at a reaction time of 48 h. The structure of products (COS‐GMAs) were identified by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR. The resulting COS‐GMAs were readily soluble in neutral water, like the original COS, and exhibited an excellent antimicrobial activity. The reactivity of COS‐GMA was investigated by the reaction with poly(vinyl alcohol) (PVA). The reaction products were found to have a lower crystallinity than PVA because of the introduction of the COS‐GMA units. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 880–887, 2001     

Analytical Description of Vapor Bubble Growth in a Superheated Liquid: A New Approach

Doklady Physics - This article presents a mathematical model of vapor bubble growth in a superheated liquid, which simultaneously takes into account both dynamic and thermal effects and includes...     

Inter- and Intra-Molecular Organocatalysis of SN2 Fluorination by Crown Ether: Kinetics and Quantum Chemical Analysis

We present the intra- and inter-molecular organocatalysis of S_N2 fluorination using CsF by crown ether to estimate the efficacy of the promoter and to elucidate the reaction mechanism. The yields of intramolecular S_N2 fluorination of the veratrole substrates are measured to be very small (<1% in 12 h) in the absence of crown ether promoters, whereas the S_N2 fluorination of the substrate possessing a crown ether unit proceeds to near completion (~99%) in 12 h. We also studied the efficacy of intermolecular rate acceleration by an independent promoter 18-crown-6 for comparison. We find that the fluorinating yield of a veratrole substrate (leaving group = −OMs) in the presence of 18-crown-6 follows the almost identical kinetic course as that of intramolecular S_N2 fluorination, indicating the mechanistic similarity of intra- and inter-molecular organocatalysis of the crown ether for S_N2 fluorination. The calculated relative Gibbs free energies of activation for these reactions, in which the crown ether units act as Lewis base promoters for S_N2 fluorination, are in excellent agreement with the experimentally measured yields of fluorination. The role of the metal salt CsF is briefly discussed in terms of whether it reacts as a contact ion pair or as a “free” nucleophile F⁻.     

Preparation and characterization of activated carbon fibers supported with silver metal for antibacterial behavior

In this work, the effect of immersion in silver nitrate solution on activated carbon fibers (ACFs) was investigated in relation to adsorption behavior and antibacterial activity of ACFs supported with silver (ACF/Ag). The pore and surface properties were studied in terms of BET volumetric measurement with nitrogen adsorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The antibacterial activities of ACF/Ag were studied in broth dilution tests against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) from a point of view of water purification. As an experimental result, the silver content of ACF/Ag increased with increasing concentration of silver nitrate. It was found that the micropore structure slightly decreased as the silver nitrate concentration increased. Otherwise, it was revealed that the ACF/Ag possessed a strong antibacterial activity and an inhibitory effect for the growing of E. coli and S. aureus, respectively. Silver content on ACF/Ag decreased rapidly because of rough morphology of silver particles in water erosion.     

Atmospheric organic aerosol production by heterogeneous acid-catalyzed reactions.

Exploratory evidence from our laboratories shows that acidic surfaces on atmospheric aerosols lead to very real and potentially multifold increases in secondary organic aerosol (SOA) mass and build-up of stabilized nonvolatile organic matter as particles age. One possible explanation for these heterogeneous processes are the acid-catalyzed (e.g., H2SO4 and HNO3) reactions of atmospheric multifunctional organic species (e.g., multifunctional carbonyl compounds) that are accommodated onto the particle phase from the gas phase. Volatile organic hydrocarbons (VOCs) from biogenic sources (e.g., terpenoids) and anthropogenic sources (aromatics) are significant precursors for multifunctional organic species. The sulfur content of fossil fuels, which is released into the atmosphere as SO2, results in the formation of secondary inorganic acidic aerosols or indigenous acidic soot particles (e.g., diesel soot). The predominance of SOAs contributing to PM2.5 (particulate matter, that is, 2.5 microm or smaller than 2.5 microm), and the prevalence of sulfur in fossil fuels suggests that interactions between these sources could be considerable. This study outlines a systematic approach for exploring the fundamental chemistry of these particle-phase heterogeneous reactions. If acid-catalyzed heterogeneous reactions of SOA products are included in next-generation models, the predicted SOA formation will be much greater and have a much larger impact on climate-forcing effects than we now predict. The combined study of both organic and inorganic acids will also enable greater understanding of the adverse health effects in biological pulmonary organs exposed to particles.     

Polyopes affinis Suppressed IFN-γ- and TNF-α-Induced Inflammation in Human Keratinocytes via Down-Regulation of the NF-κB and STAT1 Pathways

Polyopes affinis is a red algal species commonly found on the South coast and near Jeju Island, Korea. This study aimed to determine whether P. affinis extracts can inhibit the pathogenesis of T-helper-2 (Th2)-mediated inflammation in a human keratinocyte cell line of atopic dermatitis (AD). Cells were incubated with 10 ng/mL of interferon gamma (IFN-γ) and 10 ng/mL of tumor necrosis factor-alpha (TNF-α) at various concentrations of PAB (10, 30, and 60 µg/mL) and PAA (100, 500, and 1000 µg/mL) extracts. A gene-ontology (GO)-enrichment analysis revealed that PAB significantly enriched the genes associated with biological processes such as cell adhesion, immune response, inflammation, and chemokine-mediated pathways. PAB suppressed the expression of the secretory proteins and mRNAs that are associated with the thymus and the production of activation-regulated chemokines (TARC/CCL17) and macrophage-derived chemokines (MDC/CCL22). The effect of the extract on mitogen-activated protein kinases (MAPKs) was related to its inhibition of TARC/CCL17 and MDC/CCL22 production by blocking NF-κB and STAT1 activation. These results suggest that seaweed extract may improve AD by regulating pro-inflammatory chemokines. In conclusion, we first confirmed the existence of phloroglucinol, a polyphenol formed from a precursor called phlorotannin, which is present in PAB, and this result proved the possibility of PAB being used as a treatment for AD.