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1.
A. Schalchli-Plaszczynski L. Auvray 《The European physical journal. E, Soft matter》2002,7(4):339-344
We study by small-angle neutron scattering the vesicle-to-micelle transition induced by anchoring diblock copolymers on the
surfactant membranes. Vesicles are made using the ternary system SDS (sodium dodecyl sulfate)/octanol/PS-POE (polystyrene-polyoxyethylene),
chosen as a model of more complex biological systems. The anchored polymer chains destabilize the membranes and lead to the
formation of mixed polymer-surfactant micelles. We show that there is no influence of the polymer mass on the membranes destabilization.
We compare this experimental result with recent theoretical predictions concerning the polymer-grafted membranes. We have
a good agreement with predictions involving membrane curvature effects, and also with predictions focusing on more local deformations
of membranes created by the grafted chains.
Received 12 June 2001 and Received in final form 18 March 2002 相似文献
2.
Papadakis CM Rittig F Almdal K Mortensen K Stĕpánek P 《The European physical journal. E, Soft matter》2004,15(4):359-370
The structure and dynamics of a strongly asymmetric poly(ethylene propylene)-poly(dimethylsiloxane) (PEP-PDMS) diblock copolymer in the melt have been studied over a wide temperature range. Small-angle neutron scattering reveals that the sample exhibits two stable phases in this temperature range: Above the order-to-disorder transition temperature, it is disordered, whereas the domain structure is body-centered cubic (bcc) below, being stable down to the lowest temperatures measured. In the disordered state, dynamic light scattering (DLS) in the polarized geometry reveals the heterogeneity mode and the cluster mode. In the bcc phase, the PEP and the PDMS blocks form the micellar cores and the matrix, respectively. Here, two modes are observed in DLS, and the diffusion coefficients measured using pulsed field gradient (PFG) NMR are broadly distributed with the most probable diffusion coefficient coinciding with the slow DLS mode. We attribute the fast process in the bcc state to concentration fluctuations of the micellar cores (PEP), relaxing by mutual diffusion of the micelles with copolymers dissolved in the PDMS matrix. The slower process in the bcc state is ascribed to activated long-range self-diffusion of single copolymers from micelle to micelle through the PDMS matrix. This assignment is corroborated by the good coincidence of the reduced diffusivities with the ones from the literature. However, this mode may also be assigned to the rearrangement of entire micelles.This paper is dedicated to the memory of G. Fleischer 相似文献
3.
We present small angle neutron scattering measurements on binary aqueous solutions of some short-chain amphiphiles (diols,
triols, glycols and diglycols) at room temperature. The spectra were analysed in terms of the Teubner-Strey phenomenological
formula which allows to obtain a measure for the amphiphilicity strength of each system (amphiphilicity factor f
a). In some systems, however, other models, valid for micellar solutions, give also a good representation of the spectra. As
a result, we find that, independently of the type of hydrophilic group side (oxydrilic or oxirane), these systems cover the
entire accessible amphiphilicity scale ( -1 < f
a < 1). Some disordered systems ( f
a > 1) presumably are able to form micelle-like aggregates.
Received 12 June 2002 Published online: 16 April 2003
RID="a"
ID="a"e-mail: giovanni.darrigo@uniroma1.it 相似文献
4.
Structure and properties of some glass-forming liquid alloys 总被引:1,自引:0,他引:1
U. Dahlborg M. Calvo-Dahlborg P.S. Popel V.E. Sidorov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):639-648
Some physical properties (kinematic viscosity, surface tension and magnetic susceptibility) of some Fe-based metallic melts
of easily glass-forming alloys have been measured during heating and subsequent cooling. The results indicate that molten
liquid metallic alloys undergo a number of structural transformations ranging from the initial microheterogeneous state formed
after melting up to the true solution state. Studies by small angle neutron scattering on a eutectic SnPb melt confirm this
conclusion in that two families of different sizes have been seen, one in the range 1 to 2 nm and one of size larger than
100 nm. Both kind of particles have relatively sharp interfaces and the size of the smaller particles is found to depend on
temperature.
Received 25 February 1999 and Received in final form 28 October 1999 相似文献
5.
We report dynamic light scattering and small angle neutron scattering studies of the pressure-induced structural transition
of nonionic micelles of surfactant polyoxyethylene 10 lauryl ether (C12E10) in the pressure range 0 to 2000 bar. Measurements
have been performed on 1 wt% C12E10 in aqueous solution with and without the addition of KF. Micelles undergo sphere to lamellar
structural transitions as the pressure is increased. On addition of KF, rod-like micelles exist at ambient pressure, which
results in rod-like to lamellar structural transition at a much lower pressure in the presence of KF. Micellar structural
transitions have been observed to be reversible.
相似文献
6.
Neutron scattering from equilibrium-swollen networks 总被引:1,自引:0,他引:1
Sukumaran SK Beaucage G Mark JE Viers B 《The European physical journal. E, Soft matter》2005,18(1):29-36
Small-angle neutron scattering measurements were performed on end-linked poly (dimethylsiloxane) (PDMS) networks swollen to
equilibrium with d-benzene. Comparison was made with equivalent concentration PDMS solutions. Equilibrium-swollen networks
consistently displayed a linear scattering regime at low q followed by a good-solvent-like scaling regime at high q in agreement with the predictions of the Gel Tensile Blob (GTB) model. Data are fit using the unified function modified for
the GTB model (3-parameter fit). Equilibrium-swollen networks display a base structural size, the gel tensile-blob size, ξ,
that was found to be independent of the molecular weight between crosslinks for the series of molecular weights studied, consistent
with the predictions of the model. The length of the extended tensile structure, L, can be larger than the length of the fully extended network strand. The predicted scaling relationship for L, L ∼ Q1/2Navg, where Navg = (1/fNc2+1/4Ne2
, Q is the equilibrium swelling ratio, Nc is the molecular weight between crosslinks, Ne is the entanglement molecular weight and f is the crosslink functionality is in agreement with experimental results for the networks studied. 相似文献
7.
Chen SH Mallamace F Faraone A Gambadauro P Lombardo D Chen WR 《The European physical journal. E, Soft matter》2002,9(3):283-286
We detect in a tri-block co-polymer micellar system an ergodic-to-nonergodic-to-ergodic transition, as a function of temperature,
in a range of concentrations, by photon correlation measurements. The shear viscosity is also shown to jump two order of magnitude
at these transition temperatures. Surprisingly, the structure factor as measured by small angle neutron scattering shows a
marked narrowing at the structural arrest state. Rationalization of these results with the existence of an attractive branch
in the phase diagram of an attractive colloid system predicted by mode coupling theory is made.
Received 9 Aprile 2002 相似文献
8.
Bellour M Skouri M Munch JP Hébraud P 《The European physical journal. E, Soft matter》2002,8(4):431-436
We have measured the mean-square displacement of colloidal particles embedded in a semi-dilute solution of worm-like micelles,
using diffusing wave spectroscopy. This allowed us to describe their rheological properties over a very wide time range. At
very short times, the particles diffuse freely in the solvent, and then, they experience the characteristic relaxation times
of the living chains. We deduced directly, from the mean-square displacement of the particles, the mechanical properties of
the micellar solution, not only in the high-frequency regime, but also in the low-frequency range, in which we compared our
results with direct mechanical measurements, and found good agreement.
Received 22 March 2002 and Received in final form 5 June 2002 相似文献
9.
W. Essafi F. Lafuma C.E. Williams 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(2):261-266
We show experimentally that Manning counterion condensation also leads to a renormalization of the charge density at high
concentrations of highly charged, flexible, hydrophilic polyelectrolytes. Investigations by small angle neutron and X-ray
scattering of semi-dilute solutions of poly(acrylamide-co-sodium-2-acrylamido-2-methylpropane sulfonate) at different charge densities above the condensation threshold, show that
the scattering function is invariant with the charge density.
Received 16 June 1998 相似文献
10.
A. Steyerl B.G. Yerozolimsky A.P. Serebrov P. Geltenbort N. Achiwa Yu.N. Pokotilovski O. Kwon M.S. Lasakov I.A. Krasnoshchokova A.V. Vasilyev 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):299-304
Ultracold neutrons (UCN) are lost from traps if they are quasi-elastically scattered from the wall with an energy gain sufficient
to exceed the Fermi potential for the wall. Possible mechanisms of a quasi-elastic energy transfer are, for instance, scattering
from hydrogen diffusing in an impurity surface layer or on surface waves at a liquid wall. Using two different experimental
methods at the UCN source of the Institut Laue-Langevin we have investigated both the energy-gain and the energy-loss side
of quasi-elastic UCN scattering on Fomblin grease coated walls. For Fomblin oil and similar new types of oil we report up-scattering
data as a function of temperature and energy transfer. These low-temperature oils may be used in an improved measurement of
the neutron lifetime, which requires extremely low wall reflection losses.
Received 13 March 2002 Published online 31 July 2002 相似文献
11.
Rivière C Wilhelm C Cousin F Dupuis V Gazeau F Perzynski R 《The European physical journal. E, Soft matter》2007,22(1):1-10
The internal structure of biological vesicles filled with magnetic
nanoparticles is investigated using the following complementary analyses:
electronic transmission microscopy, dynamic probing by magneto-optical
birefringence and structural probing by Small Angle Neutron Scattering
(SANS). These magnetic vesicles are magnetic endosomes obtained via a
non-specific interaction between cells and anionic magnetic iron oxide
nanoparticles. Thanks to a magnetic purification process, they are probed at
two different stages of their formation within HeLa cells: (i) adsorption of
nanoparticles onto the cellular membrane and (ii) their subsequent
internalisation within endosomes. Differences in the microenvironment of the
magnetic nanoparticles at those two different stages are highlighted here.
The dynamics of magnetic nanoparticles adsorbed onto cellular membranes and
confined within endosomes is respectively 3 and 5 orders of magnitude slower
than for isolated magnetic nanoparticles in aqueous media. Interestingly,
SANS experiments show that magnetic endosomes have an internal structure
close to decorated vesicles, with magnetic nanoparticles locally decorating
the endosome membrane, inside their inner-sphere. These results, important
for future biomedical applications, suggest that multiple fusions of
decorated vesicles are the biological processes underlying the endocytosis
of that kind of nanometric materials. 相似文献
12.
Gotter M Sottmann T Baciu M Olsson U Wennerström H Strey R 《The European physical journal. E, Soft matter》2007,24(3):277-295
Time-resolved small-angle neutron scattering (TR-SANS) was employed to observe temperature-induced phase transitions from
the sponge (L
3 to the lamellar ( L
α phase, and vice versa, in the water-oil (n -decane)-non-ionic surfactant ( C12E5 system using both bulk and film contrast. Samples of different bilayer volume fractions φ and solvent viscosities η were
investigated applying various amplitudes of temperature jump ΔT . The findings of a previous 2H -NMR study could be confirmed, where the lamellar phase formation was determined to occur through a nucleation and growth
process, while it was concluded that the L
3 -phase develops in a mechanistically different and more rapid manner involving uncorrelated passage formation. Likewise,
the kinetic trends of the nucleation and growth transition (decreased transition time with increase of φ and ΔT were witnessed once again. Additionally, NMR and SANS data that demonstrate a strong dependency of that process on solvent
viscosity η are presented. Contrariwise, it is made evident via both SANS and NMR results that the L
α -to-L
3 transition time is independent (within experimental sensitivity) of the varied parameters (φ , ΔT , η . Unusual scattering evolution in one experiment, originating from a highly ordered lamellar phase, intriguingly hints
that a major rate determining factor is the disruption of long-range order. Furthermore, the bulk contrast investigations
give insight into structure peak shifts/development during the transitions, while the film contrast experiments prove the
bilayer thickness to be constant throughout the phase transitions and show that there is no evidence for a change in the short-range
order of the bilayer structure. The latter was considered possible, due to the different topology of the L
3 and L
α phases. Lastly, an unexpected yet consistent appearance of anisotropic scattering is detected in the L
3 -to- L
α transitions. 相似文献
13.
L. Saviot E. Duval J.F. Jal A.J. Dianoux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):661-666
Relaxations in amorphous bis-phenol A polycarbonate are studied by neutron scattering, as a function of temperature below
the glass transition. Two different processes are observed. One is very fast, with a characteristic time (∼ 0.3 ps), that
is independent of temperature and momentum transfer. Conversely the other is slower, with a time which is dependent on temperature
and momentum transfer. The very fast localized anharmonic motion is interpreted by the overdamping of low-frequency vibrational
modes, by nearby dynamic holes. The slower relaxation is thermally activated and momentum transfer dependent. It corresponds
to molecular group motions and possibly to the short-time regime of the segmental relaxation.
Received 29 February 2000 and Received in final form 13 June 2000 相似文献
14.
G.H. Fredrickson F.S. Bates 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(1):71-76
We suggest that ABC triblock copolymers provide a convenient and effective route to emulsifying blends of A and C homopolymers
into co-continuous morphologies over a wide range of compositions. Direct transitions between disordered tricontinuous phases
(“ABC microemulsions”) and spatially-periodic tricontinuous phases (e.g. gyroid or double-diamond cubic phases) should be possible in appropriately formulated alloys. We envision a broad range of
potential applications to thermoplastic and thermoset polymeric materials.
Received: 4 June 1997 / Revised: 17 September 1997 / Accepted: 13 October 1997 相似文献
15.
Spherical polyelectrolyte block copolymer micelles: Structural change in presence of monovalent salt
Muller F Guenoun P Delsanti M Demé B Auvray L Yang J Mays JW 《The European physical journal. E, Soft matter》2004,15(4):465-472
Spherical polyelectrolyte block copolymer micelles were investigated as a function of added NaCl salt concentration using Small-Angle Neutron Scattering (SANS) and Light Scattering (LS). The micelles are formed by the self-association of charged-neutral copolymers made of a long deuterated polyelectrolyte moiety (NaPSSd)251 and a short hydrophobic moiety (PEP)52. In presence of salt, the core shape and the aggregation number of the micelles are not affected. The hydrodynamic radius of the micelle is found to be identical to the radius of the whole micelle deduced from neutron scattering and thus the hydrodynamic radius is a valid measure of the corona thickness. At the lowest salt concentrations investigated the thickness of the corona, Rs, remains essentially constant and a contraction is observed above an added-salt concentration cs of 2×10-2 M where this crossover concentration corresponds to the average ionic strength of the free counterions in the corona. The contraction takes place while maintaining a rod-like behavior of the chains at short scale and obeys to: Rs cs-0.18. The exponent 0.18 suggests an electrostatic persistence length proportional to the Debye screening length. 相似文献
16.
It is shown that quasielastic scattering of ultracold neutrons due to diffusive motion of scatterers at the surface of liquid
polymer (fomblin) or adsorbed hydrogenous contaminations of the surface of neutron traps may be possible reason of their energy
spreading during long storage time in closed traps, which was observed in the recent experiments.
Received 8 July 1998 相似文献
17.
V. Fourmaux-Demange A. Brûlet F. Boué P. Davidson P. Keller J.P. Cotton 《The European physical journal. E, Soft matter》2000,1(4):301-317
We have studied the rheology and the conformation of stretched comb-like liquid-crystalline polymers. Both the influence of
the comb-like structure and the specific effect of the nematic interaction on the dynamics are investigated. For this purpose,
two isomers of a comb-like polymetacrylate polymer, of well-defined molecular weights, were synthesized: one displays a nematic
phase over a wide range of temperature, the other one has only an isotropic phase. Even with high degrees of polymerization
N, between 40 and 1000, the polymer chains studied were not entangled. The stress-strain curves during the stretching and relaxation
processes show differences between the isotropic and nematic comb-like polymers. They suggest that, in the nematic phase,
the chain dynamics is more cooperative than for a usual linear polymer. Small-angle neutron scattering has been used in order
to determine the evolution of the chain conformation after stretching, as a function of the duration of relaxation t
r. The conformation can be described with two parameters only: , the global deformation of the polymer chain, and p, the number of statistical units of locally relaxed sub-chains. For the comb-like polymer, the chain deformation is pseudo-affine:
is always smaller than (the deformation ratio of the whole sample). In the isotropic phase, has a constant value, while pincreases as tr. This latter behavior is not that expected for non-entangled chains, in which p varies as t
r
1/2 (Rouse model). In the nematic phase, decreases as a stretched exponential function of t
r, while p remains constant. The dynamics of the comb-like polymers is discussed in terms of living clusters from which junctions are
produced by interactions between side chains. The nematic interaction increases the lifetime of these junctions and, strikingly,
the relaxation is the same at all scales of the whole polymer chain.
Received 5 May 1999 and Received in final form 18 October 1999 相似文献
18.
Trabelsi S Guillot S Ritacco H Boué F Langevin D 《The European physical journal. E, Soft matter》2007,23(3):305-311
Small-angle neutron scattering measurements were performed on dilute solutions of carboxymethylcellulose/DTAB complexes in
water in order to determine their size, shape and internal structures. At low polymer content, the complexes are spherical,
rather monodisperse and probably made of polymer chains intercalated between surfactant micelles. Moreover, we show that these
micelles have a similar cubic arrangement than found in polymer/surfactant precipitates formed at higher surfactant concentrations.
At larger polymer content, in the semi-dilute polyelectrolyte regime, the complexes are larger, softer and polydisperse. However,
they possess a similar internal structure in both regimes. Carboxymethylcellulose/CTAB complexes are also large, soft and
polydisperse but do not seem to exhibit well-defined internal structures. 相似文献
19.
T. Striffler U. Stuhr H. Wipf H. Hahn S. Egelhaaf 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):245-251
By means of small-angle neutron scattering the microstructure of two nanocrystalline Pd samples (prepared by inert gas condensation)
has been studied at room temperature in a Q-range from [0pt] to [0pt] . An additional subsequent doping of the two samples with H as well as with D (concentrations < 4 at%) caused contrast variations
that provided more detailed structural information. The measured scattering intensity was modeled by a Porod contribution
from large heterogenities (e.g. pores) and a contribution from spherical grains with a log-normal distribution of their radii. To account for the presence
of grain boundaries, the grains were considered to be surrounded by a shell with a reduced Pd density and a thickness half
as large as the thickness of the grain boundaries. For the above model, the data of the H-doped, D-doped and undoped sample
were simultaneously fitted with one single set of adjustable parameters. The fits yielded for the two samples volume-weighted
mean grain radii of 10 nm and 13 nm. The values for the grain boundary thickness lie between 0.2 and 0.8 nm. Almost all of
the H- and D-atoms are, at low hydrogen concentrations, located in the grain boundaries.
Received 1 May 2000 相似文献
20.
Higgins AM Sferrazza M Jones RA Jukes PC Sharp JS Dryden LE Webster J 《The European physical journal. E, Soft matter》2002,8(2):137-143
We investigate the dynamics of spinodal dewetting in liquid-liquid polymer systems. Dewetting of poly(methyl-methacrylate)
(PMMA) thin films on polystyrene (PS) “substrates” is followed in situ using neutron reflectivity. By following the development of roughness at the PS/PMMA interface and the PMMA surface we extract
characteristic growth times for the dewetting process. These characteristic growth times are measured as a function of the
molecular weight of the two polymers. By also carrying out experiments in the regime where the dynamics are independent of
the PS molecular weight, we are able to use dewetting to probe the scaling of the PMMA thin film viscosity with temperature
and molecular weight. We find that this scaling reflects bulk behaviour. However, absolute values are low compared to bulk
viscosities, which we suggest may be due in part to slippage at the polymer/polymer interface.
Received 25 June 2001 and Received in final form 5 December 2001 相似文献