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221.
Thermodynamic parameters for acid dissociation of the conjugate acids of poly(N-vinylimidazole) and polyallylamine have been determined in the presence of sodium chloride and sodium nitrate. Even though
the plots of ΔG
0 against the degree of dissociation, α, are highly dependent on the added salt concentration levels, the concentration effect
has never been observed for the corresponding ΔH
0 versus α plots. The effect on the ΔG
0 versus α plots has been attributed to the entropy change of the counterions between a polyelectrolyte phase and a bulk solution
phase. The α dependency of ΔH
0 is affected remarkably by the kinds of cationic polymers and counter-anions. Each ΔH
0 value at completely neutralized conditions is quite close to the corresponding ΔH
0 value of the monomer analog. The difference in the ΔH
0 values at fully charged conditions has been explained by the heats due to
The ion-pair formation of chloride anion to the conjugate acids of poly(N-vinylimidazole) and polyallylamine has been supported by 35Cl NMR measurement. It has also been suggested that chloride anions bind the basic polymer molecules even at fully neutralized
conditions.
Received: 2 June 1999/Accepted in revised form: 19 July 1999 相似文献
222.
Guo‐Qing Bian Takayoshi Kuroda‐Sowa Sayuri Sugimoto Masahiko Maekawa Megumu Munakata 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):m144-m146
The title one‐dimensional chain polymer complex, [Mn(C6H4NO3)Cl(C6H5N)2]n, was isolated from the reaction of MnCl2 with 6‐oxo‐1,6‐dihydropyridine‐2‐carboxylic acid (HpicOH) in pyridine. The asymmetric unit contains one [Mn(HPicO)Cl(py)2] moiety (py is pyridine), with the (HpicO)− ligand acting in a tridentate manner via the two carboxylate O atoms and the pyridone O atom. The operation of inversion centres generates eight‐ and 14‐membered rings and, in conjunction with an a‐axis translation, leads to an infinite chain extending along [100]. The Mn⋯Mn separations in this chain are 5.1069 (6) and 7.1869 (6) Å. The MnII atom has a distorted octahedral coordination, with trans‐axial pyridine ligands and with three O atoms and the Cl atom in the equatorial plane. The conformation of the 14‐membered ring is stabilized by pairs of inversion‐related N—H⋯O hydrogen bonds. 相似文献
223.
A technique of pulsed-field-gradient spin-echo (PGSE) NMR combined with a quadrupole-coil rotation was applied to the study of anisotropic self-diffusion in smectic A liquid crystals. Diffusion anisotropy was found to be inverted by chemical substitution of the terminal groups in homologous compounds: Namely, the diffusion across the layer is faster for the cyano compound, whereas the diffusion within the layer is faster for the trifluoromethoxy compound. 相似文献
224.
The effects of three kinds of cyclodextrins (CyDs), alpha-, beta- and gamma-CyD on biological membranes were investigated by changes in absorption of a non-absorbable drug, sulfanilic acid (SA), from the rat small intestine and rectum using an in situ perfusion technique. The absorption of SA from the intestine was slight and was not affected by the addition of CyDs. After pretreatment with a mucolytic agent, N-acetyl-L-cysteine (N-Ac), the absorption of SA was increased compared with SA alone in the presence of only beta-CyD. Similar treatment with sodium deoxycholate (SDC) and sodium lauryl sulfate (SLS) to gastro-intestinal membrane showed the enhanced absorption of SA by the addition of beta-CyD. The mucin layer on the surface of the gastro-intestinal membrane may play an important role in the absorption of drugs. On the other hand, enhanced absorption of SA from the rat rectum was not induced by beta-CyD with or without pretreatment with N-Ac, SDC or SLS. Simultaneously, the release of neutral sugars in the perfusate after treatment with adjuvants was also observed with N-Ac, SDC and SLS. These results indicate that the mucin layer works as a barrier to the increased absorption of SA by beta-CyD. 相似文献
225.
Shizuo Miyajima 《Semigroup Forum》1992,45(1):226-240
Communicated by R. Nagel 相似文献
226.
Proton NMR experiment was carried out on a pure re-entrant nematic liquid crystal OBBC in nematic (N), smectic A(SA), and re-entrant nematic (RN) phases. The re-entrant phase transition was detected by measuring the rotation pattern (θ0-dependence) of the spectra in the external field. The dipolar splitting at θ0=0 showed smooth temperature-dependence through the phase changes, RN?SA?N. Orientational order of the molecular core is thus hardly affected by the formation of 1-D density modulation. The temperature-dependence of the spin-lattice relaxation rate showed that translational self-diffusion is the predominant mechanism of relaxation in RN, but the director fluctuation is quite significant in N. 相似文献
227.
S. Shibata K. Miyajima H. Yoshikawa T. Yano M. Yamane 《Journal of Sol-Gel Science and Technology》2000,19(1-3):665-669
The formation of cellular patterns, known as Bénard cell, was investigated in organic-inorganic hybrid films under various conditions. The cells were observed in undoped-hybrid films, and its origin was attributed to the convection of TiO2 nanoparticles formed in the aging process of the sol. These cells showed the particular properties such as the difference between the center and its surrounding: the center showed a lower refractive index than that of the surrounding, a valley at the center with mountain-like surroundings, and a hydrophobic center and hydrophilic surrounding. How the cell patterns were formed depended on the conditions such as the atmospheric humidity and the gravity. It should be also noted that the cells on a silica glass substrate remained after 1000°C heating. 相似文献
228.
229.
2-Aryl-1-phenyl-5-styrylphospholes were prepared in good yields in a one-pot procedure from the corresponding 1,9-diarylnona-8-ene-1,6-diynes and dichloro(phenyl)phosphine via intermediary titanacyclopentadienes. According to the UV-vis absorption and fluorescence spectra of this class of compounds, the optical properties of the phosphole-vinylene-bridged pi-conjugated system have been revealed to depend strongly on the electronic character of the terminal functionalities. In particular, the polarizability at the excited-state has been found to be considerably greater than that in the ground state. High molecular hyperpolarizabilities obtained for the push-pull type of 2-aryl-5-styrylphospholes in the hyper-Rayleigh scattering measurements demonstrate the potential utility of the stilbene-type phosphole derivatives as a new class of second-order NLO chromophores. 相似文献
230.
Prof. Dr. Koji Kano Toshiro Ochi Sayuri Okunaka Yusuke Ota Keiichi Karasugi Takunori Ueda Dr. Hiroaki Kitagishi 《化学:亚洲杂志》2011,6(11):2946-2955
Poly(acrylic acid) (PAA) is modified by 5‐(4‐β‐alanylaminophenyl)‐10,15,20‐tris(4‐sulfonatophenyl) porphinatoiron(III) to yield iron porphyrin‐bearing PAAs (FeP(n)s) through a condensation reaction. FeP(n)s were further functionalized by Py3CD, which is a per‐O‐methylated β‐cyclodextrin (CD) dimer with a pyridine linker and includes the porphyrin pendants to form ferric hemoCD‐P(n)s. Ferrous hemoCD‐P(3), having three porphyrin chromophores in a polymer chain, is shown to bind molecular oxygen (P1/2=7.9±1.4 Torr) in aqueous solution at pH 7.0 and 25 °C, affording oxy‐hemoCD‐P(3). Oxy‐hemoCD‐P(3) is biphasically autoxidized to ferric hemoCD‐P(3), with 27 % of the dioxygen adducts being rapidly oxidized. The rate of autoxidation of oxy‐hemoCD‐P(15), having 15 porphyrin chromophores in a polymer chain, was much faster than that of oxy‐hemoCD‐P(3), thus suggesting self‐catalyzed autoxidation of oxy‐hemoCD‐P(n)s. Oxy‐hemoCD‐P(n)s are markedly stabilized by catalase, thereby indicating that hydrogen peroxide generated from oxy‐hemoCD‐P(n) accelerates the autoxidation. Most of the hemoCD‐P(3) molecules injected into the femoral vein of a rat remained in the body, though about 16 % of the hemoCD‐P(3) molecules were excreted in the urine as a carbon monoxide adduct. 相似文献