排序方式: 共有13条查询结果,搜索用时 31 毫秒
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E. A. Lysenko A. I. Kulebyakina R. S. Grinevich P. S. Chelushkin A. B. Zezin 《Polymer Science Series A》2012,54(4):255-263
Joint micellization of two amphiphilic diblock copolymers is studied by velocity sedimentation, transmission electron microscopy,
electrophoretic mobility measurements, and static light scattering. One of the diblock copolymers is a strong polyelectrolyte
(polystyrene-block-poly(N-ethyl-4-vinylpyridinium bromide)), while the second one is a weakly charged or uncharged copolymer (polystyrene-block-poly(acrylic acid) or polystyrene-block-poly(4-vinylpyridine)). It is shown that the mixing of the diblock copolymers in a selective aqueous-organic solvent (DMF-methanol-water)
leads to the formation of joint (hybrid) micelles and that the composition of these micelles is close to the composition of
the polymer mixture. Micelles consist of an insoluble polystyrene core and a mixed corona composed of blocks of a strong polyelectrolyte
and a weakly charged or uncharged copolymer. Aqueous dispersions of mixed micelles are obtained with the use of the dialysis
technique, the spherical morphology of the micelles is ascertained, and their three-layered structure is proposed. The nonlinear
dependence of the molecular mass of micelles on their composition is found. The decisive effect of electrostatic repulsion
between strong polyelectrolyte units on the thermodynamics of micellization and the dispersion stability and molecular-mass
characteristics of the mixed micelles is demonstrated. 相似文献
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Local mobility and structure of cationic amphiphilic diblock copolymer micelles in aqueous solutions
M. V. Motyakin E. A. Lysenko P. S. Chelushkin L. L. Yasina A. M. Vasserman 《Polymer Science Series A》2010,52(3):235-242
The local mobility and organization of micelles formed by the cationic diblock copolymer PS-poly(N-ethyl-4-vinylpyridinium bromide) in dilute aqueous solutions is studied by spin-probe ESR spectroscopy. Micelles composed
of a hydrophobic PS core and a lyophilizing polyelectrolyte corona are prepared by two methods: dialysis from a nonselective
solvent and direct dispersion of the diblock copolymer in water under long-term heating. Velocity-sedimentation studies and
static and dynamic light-scattering measurements show that the micelles obtained by dialysis have smaller mean hydrodynamic
sizes and weight-average molecular masses and are less polydisperse than micelles prepared by direct dispersion. The ESR spectra
of spin probes localized in micelles of both types are found to be identical. This finding suggests that their local structure
is independent of the dispersion procedure and molecular-mass characteristics. Probes are localized in the outer layer of
the PS core near the core/shell boundary, and their local mobility is a factor of ∼2 higher than the local mobility of probes
in the phase of the solid PS. It is inferred that the structure of the outer layer of the PS core in micelles is looser than
the structure of PS in the solid phase. The localization sites of spin probes are partially penetrated by water. 相似文献
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S. V. Burov K. V. Polyanichko P. S. Chelushkin M. Yu. Dorosh I. I. Gavrilova A. V. Dobrodumov Yu. V. Pokhvoshchev V. D. Krasikov E. F. Panarin 《Doklady Chemistry》2016,466(1):18-20
In order to prepare polymeric contrast agents, various ways of modification of N-vinylpyrrolidone copolymers with vinylamine or acrolein with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid derivatives were investigated. 相似文献
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EA Lysenko AI Kulebyakina PS Chelushkin AM Rumyantsev EY Kramarenko AB Zezin 《Langmuir : the ACS journal of surfaces and colloids》2012,28(34):12663-12670
Mixed polymer micelles with hydrophobic polystyrene (PS) core and ionic amphiphilic poly(4-vinylpyridine)/poly(N-ethyl-4-vinylpyridinium bromide) corona (P4VP/PEVP) spontaneously self-assembled from mixtures of PS-b-PEVP and PS-b-P4VP macromolecules in dimethylformamide/methanol/water selective solvent. The fraction of PEVP units in corona was β = [PEVP]/([PEVP] + [P4VP]) = 0.05-1.0. Micelles were transferred into pure water via dialysis technique and pH was adjusted to 9, where P4VP blocks are insoluble. Structural characteristics of micelles as a function of corona composition β were investigated. Methods of dynamic and static light scattering, electrophoretic mobility measurements, sedimentation velocity, transmission electron microscopy, and UV spectrophotometry were applied. Spherical morphology with core (PS)-shell (P4VP)-corona (PEVP) organization was postulated. Micelles demonstrated a remarkable inflection in structural characteristics near β ~ 0.5-0.7. Above this region, aggregation number (m), core and corona radii of mixed micelles coincided with those of individual PS-b-PEVP micelles. When β decreased below 0.5, dramatic growth of aggregation number was observed, accompanied by growth in micelle size and stretching PEVP chains. At β below 0.2, dispersions of mixed micelles were unstable and easily precipitated upon addition of NaCl. Scaling relationships between micelle characteristics and β were obtained via minimization the micelle free energy, taking into account electrostatic, osmotic, volume, and surface contributions. Theoretical estimations predicted dramatic influence of β on aggregation number, m ~ β(-3). This result is in general agreement with experimental data and confirms the correctness of the core-shell-corona model. The inflection in micelle characteristics entails drastic changes in micelle dispersion stability in the presence of oppositely charged polymeric (sodium polymethacrylate) or amphiphilic (sodium dodecyl sulfate) complexing agents. 相似文献
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Chelushkin PS Lysenko EA Bronich TK Eisenberg A Kabanov VA Kabanov AV 《The journal of physical chemistry. B》2008,112(26):7732-7738
The present study investigates the relationship between the aggregation state and dynamic properties of block ionomer complexes (BICs) based on amphiphilic ionic block copolymers. The polyion coupling of 4'-(aminomethyl)fluorescein (AMF)-labeled poly(sodium methacrylate) (PMANa) or polystyrene- block-poly(sodium carboxylates) with poly(N-ethyl-4-vinylpyridinium bromide), PEVP was studied at an excess of carboxylate groups [PEVP]/[COO(-)] TOTAL = 0.3 and detected by fluorescence quenching. The polyion interchange reactions included migration of PEVP between the following: (1) two linear polyanion chains, (2) linear polyanion chain and anionic polyion shell micelle, or (3) two anionic polyion shell micelles. Additionally, the interchange of AMF-labeled PMANa with unlabeled PMANa in the shell of polystyrene- block-PEVP micelles was studied. The interchange reactions were carried out at [PEVP]/[COO(-)] TOTAL = 0.15 and detected by fluorescence quenching (direct reaction) or ignition (reverse reaction). The rates of these reactions were compared using half-conversion times and, when possible, second-order reaction kinetic constants. The dependences of the rates on the ionic strength and polyion length observed for BICs were similar to those previously reported for regular interpolyelectrolyte complexes (IPECs) of linear polyions. However, the interchange reactions involving polyion shell micelles were much slower than those reactions observed in IPECs. The coupling reactions involving polyion shell micelles were also slower compared with the coupling of linear polyions. The observed phenomena were attributed to the aggregation state of polyion shell micelles and discussed using the collision model for polyion interchange reactions previously proposed for IPECs. 相似文献