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991.
Takeshi Serizawa Hidetada Goto Akio Kishida Takeshi Endo Mitsuru Akashi 《Journal of polymer science. Part A, Polymer chemistry》1999,37(6):801-804
The ultrathin polymer films that were composed of biodegradable and naturally occurring chitosan and poly(γ‐benzylglutamate) were stably deposited onto a quartz crystal microbalance (QCM) by alternate immersion of a QCM from their aqueous solutions in the presence of water‐soluble organic solvents as a USS soluble solvent. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 801–804, 1999 相似文献
992.
Kazuo Suwa Yoshihiro Wada Akio Kishida Mitsuru Akashi 《Journal of polymer science. Part A, Polymer chemistry》1997,35(16):3377-3384
A novel thermosensitive poly(N-vinylisobutyramide)(polyNVIBA) hydrogel was prepared by the copolymerization of N-vinylisobutyramide (NVIBA) with butylene-bis-NVA(B-BNVA) as a crosslinker in a high yield. The swelling transition behavior was examined in comparison with poly(N-isopropylacrylamide)(polyNIPAAm) hydrogel. The resulting polyNVIBA hydrogel clearly showed a swelling transion in water at ca. 41°C. To control the transition temperature (Tt) of the gel, crosslinked copolymers of NVIBA and N-vinylacetamide (NVA) were prepared and compared with copolymers of N-isopropylacrylamide(NIPAAm) and NVA. The incorporation of NVA led to a higher swelling transition temperature. Tt of poly(NVIBA-co-NVA) gels was almost the same as those in water-soluble poly(NVIBA-co-NVA). The responses for a swelling transition of polyNVIBA and poly(NVIBA-co-NVA) gels were sharp in comparison to polyNIPAAm gels. PolyNVIBA and poly(NVIBA-co-NVA) gels desorbed 98% of water above Tt. The characteristic and the mechanism of the phase transition on the hydrogels were discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3377–3384, 1997 相似文献
993.
Takashi Norisuye Akihiko Tsuboi Takahiro Sato Akio Teramoto 《Macromolecular Symposia》1997,120(1):65-76
The dilute-solution behavior and liquid crystal formation of cellulose tris(3,5-dimethylphenylcarbamate) (CTDC) in 1-methyl-2-pyrrolidone (NMP) at 25°C are discussed by summarizing our recent studies, and its molecular characteristics are compared with those of cellulose tris(phenylcarbamate) (CTC) in the same solvent. The molecular weight dependences of optical anisotropy factor, radius of gyration, intrinsic viscosity ([η]), and isotropic-cholesteric phase boundary concentration for CTDC are explained consistently by current theories based on the wormlike chain. An analysis of the newly measured [η] for CTC shows that the backbone conformation and chain stiffness are substantially the same for the two cellulose derivatives in NMP. However, a distinct difference in optical anisotropy is found and briefly discussed in relation to the higher optical resolution capacity of CTDC than that of CTC in chromatographic separation of racemic compounds. 相似文献
994.
A simple and rapid visual method for the determination of ammonia nitrogen in environmental waters using thymol 总被引:4,自引:0,他引:4
M. Okumura K. Fujinaga Y. Seike S. Honda 《Fresenius' Journal of Analytical Chemistry》1999,365(5):467-469
Simple visual and spectrophotometric methods for the determination of ammonia nitrogen in water are proposed, based on the
color development of indothymol blue formed between ammonia and thymol. The color development was accelerated by nitroprusside
to complete in 3 min. This color development is remarkably rapid compared with that of the other conventional methods with
indothymol blue and indophenol blue. The concentration range of ammonia nitrogen spectrophotometrically determined was 0.04–1.2
mg/L NH4-N. The absorbance per 1 μg NH4-N was 0.0215 (molar absorptivity = 1.51 × 104) at 690 nm. The visual method not using any instrument as an in situ method in field works was developed based on the optimum conditions for the established spectrophotometric method. This visual
method was successfully applied to the determination of ammonia nitrogen in environmental waters.
Received: 21 December 1998 / Revised: 31 May 1999 / /Accepted: 4 June 1999 相似文献
995.
On the basis of fundamental studies on elementary processes involving allyl−O and acyl−O bond cleavages, various new catalytic processes to convert carboxylic acid derivatives have been realized. The new processes include 1) carbonylation of allyl formates to β,γ‐unsaturated acids, 2) amination, alkylation, and carbonylation of allylic alcohols, 3) aldehyde synthesis by hydrogenation of carboxylic anhydrides and carboxylic acids, 4) ketone synthesis by combination of the C−O bond cleavage with transmetallation by organoboronic acids. The processes described here have advantages over the conventional ones in that they are more atom‐efficient and halogen‐free in realizing the syntheses of a variety of carbonyl‐containing compounds under mild conditions. 相似文献
996.
997.
Y Takeda K Kawagoe A Yokomizo Y Yokomizo T Hosokami Y Shimoto Y Tabuchi Y Ogihara Y Honda K Kawarabayashi M Iseri S Yokohama 《Chemical & pharmaceutical bulletin》1999,47(6):755-771
In order to improve the biological characteristics of DA-3934 (5), a novel gastrin/cholecystokinin (CCK)-B receptor antagonist, phenoxyacetic acid derivatives replacing the N-methyl-N-phenylcarbamoylmethyl moiety of 5 with various alkyl chains have been synthesized and their biological activity evaluated. The relationship between the structure of these compounds and their human gastrin receptor binding affinity showed that there should be the optimal size among the various N-alkyl chains. Also a significant increase in the receptor binding affinity was achieved by several compounds. Among those compounds, 2-[3-[3- [N-cyclohexylmethyl-N-[2-(N-methyl- N-phenylcarbamoylmethoxy)phenyl]carbamoylmethyl]ureido]pheny l]acetic acid (22c) and (+/-)-2-[3-[3-[N-[2-(N-methyl-N- phenylcarbamoylmethoxy)phenyl]-N-(3-methylpentyl)carbamoy lmethyl]ureido] phenyl]acetic acid (22h) exhibited high affinity for human gastrin receptors and were also more potent inhibitors in a pentagastrin-induced gastric acid secretion model than the parent compound, 5. The ED50 values of these compounds when administered intraduodenally to rats were 0.12 and 0.63 mg/kg, respectively. 相似文献
998.
Two geometrically isomeric γ‐cyclodextrin derivatives with a thymolphthalein moiety in the secondary hydroxyl side were prepared as guest‐responsive color change indicators. The isomers exhibit a pH dependence of their absorption spectra and a remarkable change in the absorbance around 610 nm upon guest addition. One of the isomers formed complexes of 2 : 1, the other of 1 : 1 stoichiometry (host/guest). 相似文献
999.
1000.