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1.
Li JF Fan J Zhang HD Qiu F Tang P Yang YL 《The European physical journal. E, Soft matter》2006,20(4):449-457
The spherical surface is spatially discretized with triangular lattices to numerically calculate the Laplace-Beltrami operator
contained in the self-consistent field theory (SCFT) equations using a finite volume method. Based on this method we have
developed a spherical alternating-direction implicit (ADI) scheme for the first time to help extend real-space implementation
of SCFT in 2D flat space to the surface of the sphere. By using this method, we simulate the equilibrium microphase separation
morphology of block copolymers including AB diblocks, ABC linear triblocks and ABC star triblock copolymers occurred on the
spherical surface. In general, two classes of microphase separation morphologies such as striped patterns for compositionally
symmetric block copolymers and spotted patterns for asymmetric compositions have been found. In contrast to microphase separation
morphology in 2D flat space, the geometrical characteristics of a sphere has a large influence on the self-assembled morphology.
For striped patterns, several of spiral-form and ring-form patterns are found by changing the ratio of the radius of a sphere
to the averaging width of the stripes. The specific pattern such as the striped and spotted pattern with intrinsic dislocations
or defects stems from formed periodic patterns due to microphase separation of block copolymers arranged on the curved surface. 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 here a neutron reflectivity study of the influence of an alternative electric field on a supported phospholipid
double bilayer. We report for the first time a reproducible increase of the fluctuation amplitude leading to the complete
unbinding of the floating bilayer. Results are in good agreement with a semi-quantitative interpretation in terms of negative
electrostatic surface tension. 相似文献
4.
It is well known that the morphology of block copolymer aggregates depends on polymer properties such as the molecular weight,
the relative block length, and the chemical nature of the repeat unit. Recently, we have shown that if aggregates are allowed
to self-assemble in solution, then in addition to the above factors, a high degree of control over the aggregate architecture
can be achieved by adjusting the solution conditions. Factors such as the water content in the solvent mixture, the solvent
nature and composition, the presence of additives (ions, surfactants, and homopolymer) and the polymer concentration were
successfully employed to control the aggregate shape and size. In this paper, we review a series of studies performed in our
group to show how solution properties can control the architecture of aggregates prepared from a given copolymer. The control
mechanism is explained in terms of the effect of each property on the forces that govern the formation of any given morphology,
namely the core-chain stretching, corona-chain repulsion and interfacial tension.
Received 30 April 2002 and Received in final form 3 September 2002 Published online: 21 January 2003 相似文献
5.
Qingjun Wang 《Applied Surface Science》2007,253(23):9054-9060
This paper describes a simple method for fabricating both highly hydrophobic and oleophilic meshes by coating thin fluoro-containing films. The static contact angle of such meshes is greater than 150° for water, and close to 0° for kerosene, xylene and toluene. These meshes can separate water from oil effectively without resorting to any extra power or chemical agent. Moreover, they exhibited stable water resisting, anti-chemical erosion and anti-hot aging properties. It promises as a candidate for the separation of oil and water. 相似文献
6.
This outlook paper focuses on micelles formed by ABC triblock copolymers (triblock terpolymers) and related systems resulting from mixtures of diblock copolymers. Micelles with different internal structure such as micelles with a heterogeneous core and a homogeneous corona or micelles with a homogeneous core and a mixed corona are presented. More complex nanoobjects such as vesicles and Janus particles are also reviewed. Finally, potential applications of these objects are discussed. 相似文献
7.
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
8.
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
9.
We present an experimental study of the spreading dynamics of symmetric diblock copolymer droplets above and below the order-disorder
transition. Disordered diblock droplets are found to spread as a homopolymer and follow Tanner’s law (the radius grows as
R ∼ t
m , where t is time and m = 1/10 . However, droplets that are in the ordered phase are found to be frustrated by the imposed lamellar microstructure.
This frustration is likely at the root of the observed deviation from Tanner’s law: droplet spreading has a much slower power
law ( m ∼ 0.05±0.01 . We show that the different spreading dynamics can be reconciled with conventional theory if a strain-rate-dependent
viscosity is taken into account. 相似文献
10.
L.R. Hutchings R.W. Richards R.L. Thompson D.G. Bucknall A.S. Clough 《The European physical journal. E, Soft matter》2001,5(4):451-464
Heterotelechelic deuteropolystyrenes have been synthesised with a tertiary amine functionality at one end and a fluorocarbon
group at the other end of the polymer chain. A layer of this polymer, circa 120 ? thick, has been attached to the surface of a silicon substrate and subsequently covered with a much thicker layer of
hydrogenous polystyrene. The combination has then been annealed at 413 K under vacuum for defined times and the subsequent
distribution of the deutero heterotelechelic polymer determined using nuclear reaction analysis and neutron reflectometry.
The influences of annealing time, molecular weight and thickness of the hydrogenous polymer have been examined. Nuclear reaction
analysis showed that an excess of the heterotelechelic polymer formed at both interfaces with a larger excess remaining at
the substrate-polymer interface. When the molecular weight of the hydrogenous polymer is lower than that of the deuteropolymer,
the deutero layer is initially swollen by the hydrogenous polymer but the thickness then decreases as deutero polymer becomes
detached from the silicon substrate and an additional excess layer is eventually formed at the vacuum-polymer surface. When
the molecular weight of the hydrogenous polymer is higher, there is an initial shrinkage of the deuteropolymer layer, but
the original thickness (∼ radius of gyration of the deuteropolymer) is regained on prolonged annealing. There is no evidence
for bridging between the two interfaces by the heterotelechelic polymer. After five days annealing the volume fraction distribution
of the deuteropolymer at the silicon substrate was well described by a self-consistent field model where the only adjustable
parameter was the sticking energy of the tertiary amine group to the silicon substrate for which a value of 8k
B
T was obtained. Comparison of the dependence of the equilibrium layer thickness of the deuteropolymer on the equilibrium grafting
density at the silicon surface with the predictions of scaling theory for brush-like polymer layers suggested that the grafted
molecules were in the ideal, unperturbed brush region.
Received 12 October 2000 and Received in final form 27 March 2001 相似文献
11.
A. B. Croll M. W. Matsen A. -C. Shi K. Dalnoki-Veress 《The European physical journal. E, Soft matter》2008,27(4):407-411
In the ordered state, symmetric diblock copolymers self-assemble into an anisotropic lamellar morphology. The equilibrium
thickness of the lamellae is the result of a delicate balance between enthalpic and entropic energies, which can be tuned
by controlling the temperature. Here we devise a simple yet powerful method of detecting tiny changes in the lamellar thickness
using optical microscopy. From such measurements we characterize the enthalpic interaction as well as the kinetics of molecules
as they hop from one layer to the next in order to adjust the lamellar thickness in response to a temperature jump. The resolution
of the measurements facilitate a direct comparison to predictions from self-consistent field theory. 相似文献
12.
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
13.
T. Charitat E. Bellet-Amalric G. Fragneto F. Graner 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):583-593
Single and double phosphocholine (DPPC and DSPC) bilayers adsorbed at the silicon-water interface have been prepared and characterised.
The second bilayer, called “free bilayer”, is a novel highly hydrated system floating at above the first one. Robust and reproducible preparation has been possible thanks to a combination of Langmuir-Blodgett and
Langmuir-Schaeffer techniques. Carefully optimised neutron reflectivity measurements have allowed a precise non-destructive
characterisation of the structure, hydration and roughness of the layers. This work opens new possibilities for the investigation
of the interaction between membrane lipids and soluble proteins, in particular peptides too small to be visible with other
techniques.
Received 17 July 1998 相似文献
14.
A. Karanikolas P. Tsolakis G. Bokias C. Tsitsilianis 《The European physical journal. E, Soft matter》2008,27(3):335-343
The self-organization of the double hydrophilic triblock copolymer poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene
oxide), PEO-b-P2VP-b-PEO, was investigated in dilute aqueous solution under several experimental conditions using turbidimetry,
as well as static and dynamic light scattering. As a result of the temperature-sensitive properties of the end PEO blocks
and the p H-responsive properties of the middle P2VP block, the formation of large star-like micellar nanostructures is observed at
high p H, while at low p H, but in the presence of salt and at high temperature, flower-like micelles are formed. Moreover, the viscosimetric and
dynamic light scattering studies at low p H revealed that micelle-like nanostructures are formed upon mixing the triblock copolymer with poly(acrylic acid), PAA, due
to hydrogen bonding interpolymer complexation. 相似文献
15.
Chécot F Lecommandoux S Klok HA Gnanou Y 《The European physical journal. E, Soft matter》2003,10(1):25-35
This paper discusses the self-assembly of block copolymers into vesicular morphology. After a brief state of art of the field,
a system based on an amphiphilic poly(butadiene)-b-poly(-L-glutamic acid) (PB-b-PGA) diblock copolymer in aqueous solution is discussed in detail. The aggregation behavior of this block copolymer has been
investigated by means of fluorescence spectroscopy, dynamic (DLS) and static (SLS) light scattering as well as transmission
electron microscopy (TEM). The diblock copolymer was found to form well-defined vesicles in water. The size of these so-called
polymersomes or peptosomes could be reversibly manipulated as a function of both pH and ion strength. Depending on the pH
of the aqueous solution, the hydrodynamic radii of these vesicles were found to vary from 100 nm to 150 nm. By cross-linking
the 1,2-vinyl double bonds present in the polybutadiene block, the ability to transform a transient supramolecular self-organized
aggregate into a permanent “shape-persistent stimuli-responsive nanoparticle” has been demonstrated.
Received 25 June 2002 and Received in final form 22 October 2002 Published online: 11 March 2003 相似文献
16.
Kowalewski T McCullough RD Matyjaszewski K 《The European physical journal. E, Soft matter》2003,10(1):5-16
The development of new controlled/living radical polymerization processes, such as Atom Transfer Radical Polymerization (ATRP)
and other techniques such as nitroxide mediated polymerization and degenerative transfer processes, including RAFT, opened
the way to the use of radical polymerization for the synthesis of well-defined, complex functional nanostructures. The development
of such nanostructures is primarily dependent on self-assembly of well-defined segmented copolymers. This article describes
the fundamentals of ATRP, relevant to the synthesis of such systems. The self-assembly of block copolymers prepared by ATRP
is illustrated by three examples. In the first, block copolymers of poly(butyl acrylate) with polyacrylonitrile phase separate,
leading to spherical, cylindrical or lamellar morphologies, depending on the block copolymer composition. At a higher temperature,
polyacrylonitrile block converts to nanostructured carbon clusters, whereas poly(butyl acrylate) block serves as a sacrificial
block, aiding the development of designed nanostructures. In the second example, conductive nanoribbons of poly(n-hexylthiophene)
surrounded by a matrix of organic polymers are formed from block copolymers prepared by ATRP. The third example describes
an inorganic-organic hybrid system consisting of hard nanocolloidal silica particles (20 nm) grafted by ATRP with well-defined
polystyrene-poly(benzyl acrylate) block copolymer chains (1000 chains per particle). Silica cores in this system are surrounded
by a rigid polystyrene inner shell and softer polyacrylate outer shell.
Received 9 July 2002 Published online: 11 March 2003 相似文献
17.
Ramachandran S Sunil Kumar PB Pagonabarraga I 《The European physical journal. E, Soft matter》2006,20(2):151-158
We present a Lattice-Boltzmann method for simulating self-propelling (active) colloidal particles in two dimensions. Active
particles with symmetric and asymmetric force distribution on their surface are considered. The velocity field generated by
a single active particle, changing its orientation randomly, and the different time scales involved are characterized in detail.
The steady-state speed distribution in the fluid, resulting from the activity, is shown to deviate considerably from the equilibrium
distribution. 相似文献
18.
Qiong-Gui Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(1):27-36
The interaction between a general magnetic source and a
long type-II superconducting cylinder in the Meissner or mixed state
is studied within the London theory. We first study the Meissner
state and solve the Maxwell–London equations when the source is a
magnetic monopole located at an arbitrary position. Then the field
and supercurrent for a more complicated magnetic charge distribution
can be obtained by superposition. A magnetic point dipole with
arbitrary direction is studied in detail. It turns out that the
levitation force on the dipole contains in general an angular as well
as a radial component. By integration we obtain the field and
supercurrent when the source is a two-dimensional monopole (a
magnetically charged long thread along the axial direction), from
which the results for a two-dimensional point dipole easily follow.
In the latter case the levitation force points in the radial
direction regardless of the orientation of the dipole. The case for a
current carrying long straight wire parallel to the cylindrical axis
is solved separately. The limit of ideal Meissner state is discussed
in most cases. The case of mixed state is discussed briefly. It turns
out that vortex lines along the axial direction and vortex rings
concentric with the cylinder have no effect outside the cylinder and
the levitation forces remain the same as in the case of the Meissner
state. 相似文献
19.
20.
S.-y. Xie Y.-p. Yang X. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):129-143
We study the spontaneous emission properties of a V-type three-level atom embedded in a photonic crystal with the anisotropic
dispersion relation. We show that the localized field can disappear and the diffusion field can become intense in some regions.
This originates from no singularity of the density of states. The quantum interference leads to oscillatory, quasi-oscillatory
or complete decay behavior of population. The complete decay can also be realized in certain condition without depending on
the initial state.
Received 9 April 2000 and Received in final form 1st August 2000 相似文献