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51.
Koga T 《The European physical journal. E, Soft matter》2005,17(3):381-388
The formation of intramolecular micelles in copolymers with periodic sequence, where hydrophobic units (stickers) are periodically placed along the chain, is studied by using multicanonical Monte Carlo computer simulations for an off-lattice bead-rod model in three dimensions. With decreasing the temperature, a transition from random-coil conformations to micelles occurs and flower-type micelles are formed via the transition. The number of stickers forming a micelle core is limited by the excluded-volume effect of loop chains around micelle cores. By this effect, two intramolecular micelles are formed for long polymer chains with 60 bonds via the coil-to-micelle transition. By further decreasing the temperature, we find that another transition, i.e., a micelle-to-micelle transition, takes place. At this transition point, the two intramolecular micelles merge into one micelle. Furthermore, we extend the multicanonical MC method to study elastic properties of single polymer chains with strong attractive interactions under external force fields, and study how the intramolecular micellization affects the elastic property of single polymer chains. 相似文献
52.
We investigate the structural behavior of a poly(styrene)-block-poly(acrylic acid) diblock copolymer which forms hexagonally-packed PS cylinders (C-phase) in the melt state. The water dispersion of this structure provides hairy cylinders which comprise a PAA swollen cylindrical brush with a height h tunable via its degree of ionization and the ionic strength in the solution, and a water-free, PS cylindrical core of constant radius RC. Such system constitutes an out-of-equilibrium frustrated model system: the selective swelling of the PAA brush results in a frustration of the interface curvature, which the ratio h/RC allows to quantify. Upon heating at a temperature higher than the glass transition temperature of the PS core, the glassiness of the core is relieved and the mechanical constraints arising from the selective swelling of the structure can be relaxed: the cylinders undergo a cylinder-to-sphere transition upon annealing at high temperature, when above a frustration threshold h/RC 1.8. Thanks to a careful mapping of the transition diagram, an undulating cylindrical morphology (UC) is identified between unchanged cylinders ( h/RC
1.8) and spheres ( h/RC 2.0), which appears to result from a Rayleigh-like pearling instability of the copolymer cylinders. 相似文献
53.
54.
Menger FM Bian J Seredyuk VA 《Angewandte Chemie (International ed. in English)》2004,43(10):1265-1267
55.
56.
Self-assembled microarrays of attoliter molecular vessels 总被引:1,自引:0,他引:1
Stamou D Duschl C Delamarche E Vogel H 《Angewandte Chemie (International ed. in English)》2003,42(45):5580-5583
57.
Oelschlaeger C Buhler E Waton G Candau SJ 《The European physical journal. E, Soft matter》2003,11(1):7-20
The mixed micellization between the cationic gemini surfactant [ C12H25( CH3)2N+( C2H4) N+( CH3)2 C12H25•2Br-] and the cationic cetyltrimethylammonium bromide (CTAB) in 150 mM KBr solutions has been investigated. The variation of the
cmc of the mixtures, measured by surface tension experiments, with composition revealed synergism in micelle formation. T-Jump
and light scattering experiments performed in the vicinity of the crossover volume fraction showed the existence of two micellar
populations, possibly linear and toroidal micelles. Rheological and dynamic light scattering experiments allowed to fully
characterize the linear viscoelasticity of the mixtures. These measurements revealed synergistic gains in viscoelastic properties
with a maximum of the stress-relaxation time around the equimolar composition. These effects are ascribed to a progressive
intermicellar crosslinking resulting from a continuous increase of the end-cap energy with the 12-2-12 content in the mixture.
Received: 18 November 2002 / Accepted: 8 April 2003 / Published online: 27 May 2003
RID="a"
ID="a"e-mail: candau@fresnel.u-strasbg.fr 相似文献
58.
We studied the formation of actin scaffolds in giant vesicles of dimyristoylphosphatidylcholine (DMPC). Polymerization of
actin was induced at low ionic strength through ionophore-mediated influx of Mg2+ (2 mM). The spatial organization of the filamentous actin was visualized by confocal and epifluorescence microscopy as a
function of the filaments length and membrane composition, by including various amounts of cholesterol or lipids with neutral
and positively charged polyethyleneglycol headgroups (PEG lipopolymers). In vesicles of pure DMPC, the newly polymerized actin
adsorbs to the membrane and forms a thin shell. In the presence of 2.5 mol% lipopolymers or of cholesterol at a molar fraction
x = 0.37, formation of a thin adsorbed film is impeded. A fuzzy cortex is predominantly formed in vesicles of diameter d smaller than the filament persistence length ( d ⩽ 15μm) while for larger vesicles a homogeneous network formation is favoured in the bulk of the vesicle. The fuzzy-cortex
formation is interpreted as a consequence of the reduction of the bending energy if the actin filaments accumulate close to
the vesicle wall.
Received: 17 January 2002 / Accepted: 21 March 2003 / Published online: 24 April 2003
RID="a"
ID="a"e-mail: Laurent_Limozin@ph.tum.de 相似文献
59.
Ahmed M. Eissa Michael J.P. Smith Artur Kubilis Jackie A. Mosely Neil R. Cameron 《Journal of polymer science. Part A, Polymer chemistry》2013,51(24):5184-5193
Copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)–poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne‐terminated PE‐b‐PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne‐terminated PE‐b‐PEG was prepared by etherification reaction between hydroxyl‐terminated PE‐b‐PEG (Mn ~ 875 g mol?1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2‐azidoethanol. Atmospheric pressure solids analysis probe‐mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end‐capping of PE‐b‐PEG by the azidoethyl glycoside group. The aqueous solution self‐assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate‐bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self‐assemble via electro‐formation into giant carbohydrate‐bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate‐bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5184–5193 相似文献
60.
Krishna Dan Priya Rajdev Jolly Deb Siddhartha S. Jana Suhrit Ghosh 《Journal of polymer science. Part A, Polymer chemistry》2013,51(22):4932-4943
Synthesis of a library of amphiphilic random copolymers from a single reactive pre‐polymer and their self‐assembly is reported. Post‐polymerization modifications of the parent polymer containing pendant N‐hydroxy succinimide (NHS) ester groups with various oligooxyethylene (OE) amines produce amphiphilic random copolymers with same degree of polymerization and equal extent of randomness. 1H‐NMR and FT‐IR data indicate quantitative substitution in all cases. The critical aggregation concentration (CAC) for all the polymers is estimated to be in the range of 10?5 M. Stability of these nano‐aggregates is studied by photoluminescence using time dependent F—rster Resonance Energy Transfer (FRET) between co‐encapsulated lipophilic dyes namely DiO and DiI in the hydrophobic pocket of the aggregates. These studies suggest remarkably high stability for all systems. However those with shorter hydrophilic pendant chains are found to be even more robust. Morphology is examined by high resolution transmission electron microscopy (HRTEM) which reveals multi‐micellar clusters and vesicles for polymers containing short and longer OE segments, respectively. Encapsulation efficacy is tested with both hydrophobic and hydrophilic guest molecules. All of them can encapsulate hydrophobic guest pyrene while a hydrophilic dye Calcein can be sequestered only in vesicle forming polymers. Lower critical solution temperature (LCST) is exhibited by only one polymer that contains the shortest OE chains. All polymers exhibit excellent cell viability as determined by MTT assay. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4932–4943 相似文献