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81.
Ecaterina Stela Dragan Marcela Mihai Simona Schwarz 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):213-221
Three ionic/nonionic random copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) with either t-butyl acrylamide (TBA) or methyl methacrylate (MM), were used in the preparation of some polyelectrolyte complex dispersions (PCD) with two strong polycations of integral type, poly(diallyldimethylammonium chloride) (PDADMAC), and an ionene type polycation, containing 95 mol% N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA5). The novelty of the paper is that PCDs with a high colloidal stability, both before and after the complex stoichiometry, were obtained even with hydrophilic/hydrophobic polyanions, with a high titrant addition rate (TAR), a less explored parameter, which allows a fine control of PCDs aggregation level, in salt-free aqueous solutions. The characteristics of PCDs were also correlated with the polyanion average charge density and the structure of the nonionic comonomer, at a constant TAR, the polyanion with the lowest charge density leading to the highest turbidities and the lowest colloidal stabilities. A mechanism of the PCDs colloidal stabilization as a function of TAR was suggested in the paper. 相似文献
82.
Intrinsic viscosities for a given polyelectrolyte in salt free and low-salt solvents reported in literatures are normally not comparable, because of inadequate valuation procedures. This article describes a theoretically justified reliable method, which is free of any model assumptions: The so called Wolf plot (logarithm of the relative viscosity as a function of polymer concentration) enables the unequivocal determination of intrinsic viscosities for all kinds of macromolecules, irrespective of whether they are chain molecules of different architecture or globular polymers, whether they are charged or uncharged. The validation of the method was examined by evaluation of the viscosities of a polyelectrolyte, some uncharged polymers of different architectures, uncharged polymer blends, and some literature data. 相似文献
83.
Multilayer polyelectrolyte films containing silver ions were obtained by molecular deposition method on a glass plate or a quartz substrate. The in situ Ag nanoparticles were synthesized in the multilayer polyelectrolyte films which were put into fresh NaBH4 aqueous solution. The structure and surface morphology of composite molecular deposition films were observed by UV-vis spectrophotometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tribological characteristic was investigated by AFM and micro-tribometer. It was found that the in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have lower coefficient of friction and higher anti-wear life than pure polyelectrolyte molecular deposition films. 相似文献
84.
Marguerite Rinaudo 《Structural chemistry》2009,20(2):277-289
The principal properties of polyelectrolytes in aqueous solution are reviewed; experimental data obtained about polysaccharides
in our laboratory identify the main electrostatic interactions which occur between macromolecular chains, between ionic sites
on isolated chains or between counterions and polyelectrolytes. Two examples are described. Hyaluronan, a linear alternated
copolymer type with one anionic site per repeat unit, is very soluble in water, with a persistence length around 8 nm and
a rheological behavior directly related to the molecular weight and polymer concentration in the presence of external monovalent
electrolyte. The second example is that of pectin for which the influence of the charge density is studied. It exhibits an
important ionic selectivity among divalent counterions in dilute solution with a dimer formation followed by aggregation and
gelation. 相似文献
85.
86.
Dariush?Hinderberger Gunnar?Jeschke Hans-Wolfgang?SpiessEmail author 《Colloid and polymer science》2004,282(8):901-909
The network-forming ability of a small fraction of nanosized trianions of the triarylmethyl class (TAM) with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte is studied by high-field/high-frequency (94 GHz) electron paramagnetic resonance spectroscopy. These tristar-shaped organic ions are expected to undergo both electrostatic and hydrophobic interactions with PDADMAC chains. The dependence of electron spin echo (ESE)-detected spectra of the TAM spin probe on PDADMAC concentration reveals a heterogeneous distribution of the spin-carrying counterions. One fraction of these ions forms densely packed clusters while another one is highly diluted. On varying the concentration ratio of TAM spin probe/PDADMAC, the mean distance between closest neighbors within clusters of approximately 1.5 nm does not change significantly, while their fraction increases with decreasing polyelectrolyte content. These findings indicate that the nanosized organic TAM trianions induce network formation in solutions of PDADMAC polyelectrolyte. The data are consistent with a zip-like cooperative binding effect of TAM ions, making this spin probe an interesting building block for electrostatic self-assembly.Dedicated to Professor E.W. Fischer on the occasion of his 75th birthday. 相似文献
87.
Laurent?Bourdillon Christine?WandreyEmail author 《Colloid and polymer science》2004,282(11):1247-1257
A modified synthetic boundary experiment of analytical ultracentrifugation has been employed to examine, on-line, polyelectrolyte complex formation at flat interfaces yielding highly swollen membranes/networks. Systematic experiments with sodium alginate as a polyanion and chitosan and poly(l-lysine) as polycations identified the influence of concentration, pH, molar mass, and polycation type on the membrane characteristics and the formation process. The membranes have been evaluated by five characteristics defined herein: total thickness, compactness, heterogeneity, symmetry, and growth. The results confirm the sensitivity of the method suited to elaborate general relationships for polyelectrolyte membrane design. 相似文献
88.
Vitaliy V. Khutoryanskiy Zauresh S. Nurkeeva Aibek D. Sergaziyev Janusz M. Rosiak 《European Polymer Journal》2003,39(4):761-766
The complex formation of poly-2-[(methacryloyloxy)-ethyl]trimethylammonium chloride (PMADQUAT) with poly(acrylic acid) (PAA) of different molecular weights has been studied in aqueous solutions by potentiometric, viscometric, turbidimetric and FTIR spectroscopic methods. The formation of insoluble non-stoichiometric polyelectrolyte complexes has been shown. The stability of polyelectrolyte complexes in solutions of different pH and ionic strength has been evaluated. The formation of polyelectrolyte complexes between hydrogels of PMADQUAT and linear PAA of different molecular weights has been studied. It was shown that the molecular weight of PAA considerably affects the kinetics of interaction as well as the final state of gel-polymer complex. 相似文献
89.
研究了添加不同分子量、不同带电特性的物质(如葡萄糖、PEG聚合物系列、NaCl和CMC)到成囊溶液中, 考察它们对制得的NaCS/PDMDAAC胶囊性质的影响. 同时, 测定了聚电解质稀溶液的粘度、电导、zeta电位及聚合物阴阳离子反应后的悬浊液的浊度及zeta电位. 结果表明, 通过添加物对稀电解质溶液性质的影响可判断其对胶囊特性的影响. 分析了添加物对NaCS与PDMDAAC反应的影响, 并根据溶液格子理论对胶囊的宏观特性变化提出了一个可能的微观解释. 相似文献
90.
制备了藻朊酸钠/壳聚糖聚电解质复合物复合膜,研究了进料液浓度、温度等对水/乙醇体系渗透汽化特性的影响;发现膜的不同表面接触进料液时膜的分离性能不同。同时,对其它水/有机液体系,该膜也具有优异的分离性能。 相似文献