Novel calix[4]cryptands: “Mappemonde II” and “Mill II”

Two novel calix[4]cryptands were synthesized from 1,3‐alternate calix[4]bis‐azacrown. “Mappemonde II” consists of one 1,3‐calix[4]bis‐azacrown wrapped by a benzo‐crown ether loop. “Mill II” is composed of two 1,3‐calix[4]bis‐azacrowns linked by two benzo‐crown ether strands.     

Study on air pollution monitoring in Korea using low volume air sampler by instrumental neutron activation analysis

The aim of this research was to enhance the use of nuclear analytical techniques for air pollution studies and to study the feasibility of the use of instrumental neutron activation analysis (INAA) as a routine monitoring tool to reveal environmental pollution sources. For the collection of air particulate samples, the Gent stacked filter unit, low volume sampler with Nucleopore membrane filters were used. Trace elements in samples collected at two suburban residential sites, Taejon and Wonju city in the Republic of Korea, were analyzed by INAA. Variations of the elemental concentrations were measured monthly and the enrichment factors were calculated for the fine (<2 μm EAD) and coarse size (2–10 μm EAD) fractions. The analytical data were treated statistically to estimate the relationship between the two variables, the concentrations of elements and the total suspended particulate matter. The results were used to describe the emission source and their correlation.     

Simultaneous Analysis of Some Metal Ions in Piperidinedithio-carbamate Chelates by Reversed-Phase Liquid Chromatography

Simultaneous analysis of Ni(Ⅱ), Pd(Ⅱ), Co(Ⅱ),Cu(Ⅱ) and Hg(Ⅱ) in piperidinedithio-carbamate(PDTC) chelates were investigated by reversed phase HPLC. The optimum conditions for the separation of PDTC metal chelates were examined with respect to the pH, extraction solvent and mobile phase strength. The metal ions in mixtures at trace level, chelated with PDTC, were successfully separated on Novapak Cl8 column using methanol/water(75:25) mixture as mobile phase. PDTC metal chelates were eluted in an acceptable range of capacity factor value (0     

Electrochemical and structural properties of HT-LiCoO2 and LT-LiCoO2 prepared by the citrate sol-gel method

LT-LiCoO₂ has a slightly modified structure but significantly different electrochemical properties compared to LiCoO₂ prepared at high temperature. In this study, the structure and electrochemical properties of LT-LiCoO₂ have been evaluated using Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), and electrochemical methods. According to the structural analysis, LT-LiCoO₂ has an intermediate structure between a layered and a spinel structure. The first discharge capacity of LT-LiCoO₂ is 80 mAh/g (100 μA/cm²).     

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     

Fabrication of superhydrophobic surface from a supramolecular organosilane with quadruple hydrogen bonding

A supramolecular organosilane, 2-(3-(triethoxysilyl)propylaminocarbonylamino)-6-methyl-4[1H]pyrimidinone comprising quadruple hydrogen bonds has been synthesized in one step from commercially available starting materials. The synthesized supramolecular organosilane can be stabilized and phase-separated by dimerization via the linear array of quadruple hydrogen bonds in solution. This property of the supramolecular organosilane has been exploited to fabricate structuring materials having a superhydrophobic surface property. We have successfully generated the interconnected granular structure with adequate roughness for superhydrophobicity via sol-gel process.