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11.
A spectrophotometric method for the determination of ionic surfactants with Bromophenol Blue (BPB) based on incorporation into a precipitated chitosan was studied. Cationic surfactants (CS+), such as a quaternary ammonium ion containing a long-chain alkyl group, associate with BPB2- buffered at about pH 9 to form the ion associate (CS+)2 x BPB2-. CS+ associates with anionic surfactants (AS-). In the presence of a definite amount of CS+, an increase in the amount of AS- leads to a decrease in the amount of excess CS+, and therefore to a decrease in the amount of the ion associate of CS+ with BPB2-. The addition of a chitosan dissolved in acetic acid to a solution containing these ion associates leads immediately to precipitation of the chitosan and the incorporation of the ion associates (CS+)2 x BPB2- or CS+ x AS- into the precipitated chitosan. After centrifuging, ionic surfactants can be determined by the following two methods: (1) the absorbance of the supernatant solution is measured at 590 nm. (2) After the supernatant solution is separated, the precipitate is dissolved in an acetic acid solution and the absorbance is measured at 625 nm. Because the color of the precipitate is judged by the naked eye, this can be applied to the visual method. This is a simple and rapid method for the determination of a 10(-6) M order of ionic surfactants. 相似文献
12.
Kana Nishimori Makoto Ouchi Mitsuo Sawamoto 《Macromolecular rapid communications》2016,37(17):1414-1420
A special initiator for metal‐catalyzed living radical polymerization facilitates sequence analyses by matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF‐MS) of alternating copolymers from styrene and maleimide derivatives. The initiator is a malonate‐based alkyl halide (DEMM‐Br), in which two ester groups are attached on the carbon neighboring to bromide, and poor electron density of the radical species allows determination of next unit to the initiator in resultant alternating copolymers due to the selective initiation to styrene derivative. Thanks to the well‐defined α‐end group, sequence of the oligomeric products via radical copolymerization of PMS and EMI with DEMM‐Br can be more simply analyzed by MALDI‐TOF‐MS, and indeed the following are clarified: the crossover propagation is almost perfectly controlled regardless of the injection ratio; a minor error event of the disordered alternating sequence containing St–St sequential unit could take place; the minor error can be suppressed with an excess amount of maleimide.
13.
Kaname Ohyama Kana Oyamada Naoya Kishikawa Mitsuhiro Wada Yoshihito Ohba Kenichiro Nakashima Naotaka Kuroda 《Chromatographia》2011,74(5-6):467-470
Characteristics of the chiral stationary phase with poly(l-phenylalanine) peptide selector, which was in ??-helical state, was reported. Since environmental factors affect peptide conformation, the changes in enantioselectivity were examined depending on column temperature and mobile phase conditions (ionic strength, pH, mobile phase composition). Column temperature and pH drastically affected the enantioselectivity. Based on these changes, the relation between chiral recognition and secondary structure of the peptide selector was discussed. The column stability during sequential analysis under different separation conditions was also evaluated. 相似文献
14.
An efficient method for the synthesis of 2,5-dihydroisoxazoles and isoxazoles using iodocyclization of N-alkoxycarbonyl O-propargylic hydroxylamines has been developed. 2,5-Dihydro-4-iodoisoxazole underwent the cross-coupling reactions without aromatization to afford polyfunctionalized 2,5-dihydroisoxazoles. This process was applied to the preparation of valdecoxib and its 2,5-dihydro-derivative. 相似文献
15.
Tanaka K Kukita K Ichibakase T Kotani S Nakajima M 《Chemical communications (Cambridge, England)》2011,47(19):5614-5616
Chiral lithium binaphtholate effectively catalyzed the enantioselective alkynylation of ketones using lithium acetylide as an alkynylating agent. This is the first example of the catalytic enantioselective addition of lithium acetylide to carbonyl compounds without the aid of other metal sources. 相似文献
16.
Katsuhisa Tokumitsu Akira Tanaka Kana Kobori Yuji Kozono Masahiro Yamada Koh‐Hei Nitta 《Journal of Polymer Science.Polymer Physics》2005,43(17):2259-2268
Viscoelastic properties of urethane and ester conjugation cardo polymers that contain fluorene group, 9,9‐bis(4‐(2‐hydroxyethoxy)phenyl)fluorene (BPEF), were investigated. As for the urethane‐type cardo polymers containing BPEF in the main chain, it had a high glass‐transition temperature (Tg), which was observed as the α dispersion on viscoelastic measurement, and its temperature depended on the chemical structure of the spacing unit, such as toluene diisocyanate (TDI), 4,4′‐methylene diphenyl diisocyanate (MDI), methylene dicycloexyl diisocyanate (CMDI), and hexamethylene diisocyanate (HDI). Moreover, the Tg of urethane‐type cardo copolymers with various cardo contents increased with an increase of cardo content. Owing to the increase of Tg of cardo polymers, another molecular motion can be measured at the temperature between the α and β dispersion that was assigned to the molecular motion of urethane conjugation unit around 200 K, and it was referred to as the αsub dispersion. The peak temperature of the αsub dispersion was influenced by the chemical structure of the spacing unit, but it did not change for the cardo polymer containing the same spacing unit. Consequently, it was deduced that the αsub dispersion was originated in the subsegmental molecular motions of the cardo polymers. Ester‐type cardo polymer had higher Tg in comparison with noncardo polymer that consisted of dimethyl groups (BPEP) instead of BPEF as well. The αsub dispersion was also measured at the temperature between the α and β dispersion, which was assigned to the molecular motion of ester conjugation unit, around 220 K. For ester cardo polymer, the γ dispersion was measured in a low‐temperature region around 140 K, and it was due to a small unit motion in the ester‐type cardo polymers, such as ethoxyl unit, ? C2H4O? . Moreover, the intensity of the γ dispersion of noncardo polymer was higher than that of cardo polymer, which means the molecular motion was much restricted by the cardo structure of BPEF. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2259–2268, 2005 相似文献
17.
Uemura T Kitagawa K Horike S Kawamura T Kitagawa S Mizuno M Endo K 《Chemical communications (Cambridge, England)》2005,(48):5968-5970
The first radical polymerisation of styrene in porous coordination polymers has been carried out, providing stable propagating radicals (living radicals), and a specific space effect of the host frameworks on the monomer reactivity is demonstrated. 相似文献
18.
Hamdan A.S. Al-Shamiri Maram T.H. Abou Kana Ahmed H.M. Elwahy 《Optics Communications》2010,283(7):1438-5338
The synthesis of new high-performance dyes and the implementation of new ways of incorporating the organic molecules into the solid host matrices have produced a great deal of activity in the field of solid-state dye lasers. In this article, the new laser dye, 2-(6-allyl-3-oxo-3H-xanthen-9-yl)-benzoic acid ethyl ester [AXBE] has been synthesized, and its chemical structure was confirmed by 1H NMR, 13C NMR, IR and elemental analysis. This new dye was covalently bonded with methyl methacrylate (MMA) and 2-hydroxy ethyl methacrylate (HEMA) copolymer backbone and evaluated as the active medium of the solid-state laser dye. Its optical properties were experimentally investigated. Amplified spontaneous emission (ASE) and photostability were studied by pumping the dye sample with 355 nm (8 ns) pulsed Nd-YAG laser. 相似文献
19.
Kuntrapakam Hema Kana M. Sureshan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2780-2785
The topochemical synthesis of a miscible polymer blend is described. The azide‐ and alkyne‐decorated tetrol 1 crystallizes as two different conformers. Both conformers exhibit self‐sorted head‐to‐tail alignment with proximally placed reacting groups such that topochemical polymerization yields two types of polymer chains, each containing only one type of conformer. The orientation of complementary reactive groups in one of the head‐to‐tail‐arranged conformers favors the formation of cis‐triazole linkages, and the other favors the trans‐triazole linkages. Crystals of 1 on heating gave a perfect polymer blend containing equal amounts of cis‐triazole‐linked and trans‐triazole‐linked polymers. As each conformer is H‐bonded to four conformers of the other kind, the polymerization yields a perfect polymer blend wherein each polymer chain is surrounded by chains of the other type. Thus, the molecular ordering in the prepolymerized state in a crystal is utilized to create a polymer blend. 相似文献
20.
Synthesis and Reversible Hydration of a Pseudoprotein,a Fully Organic Polymeric Desiccant by Multiple Single‐Crystal‐to‐Single‐Crystal Transformations 下载免费PDF全文
Raja Mohanrao Prof. Dr. Kana M. Sureshan 《Angewandte Chemie (International ed. in English)》2018,57(38):12435-12439
A diphenylalanine derivative, N3‐Phe‐Phe‐NHCH2CCH, was designed for topochemical azide–alkyne cycloaddition (TAAC) polymerization. This dipeptide adopted β‐sheet arrangement as designed, in its crystals, but the azide and alkyne were not fitly aligned for their topochemical reaction. However, the voids present around these groups allowed them to attain a reactive geometry upon heating and their consequent TAAC polymerization to a pseudoprotein in a single‐crystal‐to‐single‐crystal (SCSC) fashion. This motion led to the creation of channels in the product crystal and it absorbed water from the surroundings to fill these channels as H‐bonded water wire. The pseudoprotein undergo reversible hydration/dehydration in SCSC fashion many times under mild conditions: hydration at low relative humidity and dehydration at low temperature. Vapor sorption analyses suggest that this fully organic polymer might be useful as an energy‐efficient desiccant material for controlling indoor humidity. 相似文献