共查询到10条相似文献,搜索用时 265 毫秒
1.
Elastic properties of polyelectrolyte capsules studied by atomic-force microscopy and RICM 总被引:1,自引:0,他引:1
Mechanical properties of polyelectrolyte multilayer capsules were studied using a new method combining atomic-force microscopy and reflection interference contrast microscopy. By measuring the force vs. deformation for poly(styrene sulfonate)/poly(allylamine) capsules the existence of different deformation regimes depending on the applied deformation was shown. The present paper focuses on the small-deformation regime. The elastic response of the deformed capsule was studied as a function of the wall thickness and the capsule size, and showed the theoretically expected variations. The Young modulus obtained from the experiments ranges between 1.3 and 1.9 GPa.Received: 5 August 2003, Published online: 28 October 2003PACS:
46.25.-y Static elasticity - 46.70.De Beams, plates and shells - 82.35.Rs Polyelectrolytes 相似文献
2.
S. Leporatti C. Gao A. Voigt E. Donath H. Möhwald 《The European physical journal. E, Soft matter》2001,5(1):13-20
Heating-induced morphological changes of micrometer size capsules prepared by step-wise deposition of oppositely charged polyelectrolytes
onto melamine formaldehyde (MF) latex particles and biological cells with subsequent dissolution of the core have been investigated
by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). For poly(styrenesulfonate-Na salt)/poly(allylamine
hydrochloride) polyelectrolyte capsules a remarkable heating-induced shrinking is observed. An increase of the wall thickness
corresponding to the capsule diameter decrease is found. The morphology of these microcapsules after temperature treatment
is characterized. The thickening of the polyelectrolyte multilayer is interpreted in terms of a configurational entropy increase
via polyanion-polycation bond rearrangement.
Received 20 January 2000 相似文献
3.
N. Rehse C. Wang M. Hund M. Geoghegan R. Magerle G. Krausch 《The European physical journal. E, Soft matter》2001,4(1):69-76
We study the wetting behaviour of thin polystyrene (PS) films on regularly corrugated silicon substrates. Below a critical
film thickness the PS films are unstable and dewet the substrates. The dewetting process leads to the formation of nanoscopic
PS channels filling the grooves of the corrugated substrates. Films thicker than the critical thickness appear stable and
follow the underlying corrugation pattern. The critical thickness is found to scale with the radius of gyration of the unperturbed
polymer chains.
Received 6 April 2000 and Received in final form 24 August 2000 相似文献
4.
Monolayers of dioctadecyldimethylammonium bromide (DODA) at the air/water interface were used as model for charged surfaces
to study the adsorption of anionic polyelectrolytes. After spreading on a pure water surface the monolayers were compressed
and subsequently transferred onto a polyelectrolyte solution employing the Fromherz technique. The polyelectrolyte adsorption
was monitored by recording the changes in surface pressure at constant area. For poly(styrene sulfonate) and carboxymethylcellulose
the plot of the surface pressure as function of time gave curves which indicate a direct correlation between the adsorbed
amount and surface pressure as well as a solely diffusion controlled process. In the case of rigid rod-like poly(p-phenylene sulfonate)s the situation is more complicated. Plotting the surface pressure as function of time results in a curve
with sigmoidal shape, characterized by an induction period. The induction period can be explained by a domain formation, which
can be treated like a crystallization process. Employing the Avrami expression developed for polymer crystallization, the
change in the surface pressure upon adsorption of rigid rod-like poly(p-phenylene sulfonate)s can be described.
Received 1st July 2000 and Received in final form 7 December 2000 相似文献
5.
Ronny Priefer Paolo N. Grenga Todd D. Krauss Danielle M. Raymond 《Surface science》2010,604(1):59-186
The introduction of pseudo polyelectrolytes (pPE) into the field of multilayer thin films has recently been achieved with the successful combination of poly(4-vinylphenol) (PVPh) with the weak polyelectrolyte (WPE), polyallylamine hydrochloride (PAH). This paper examines the stretching of this limit by exploring the extremes of using the pPE with the strong polyelectrolyte (SPE), poly(diallyldimethylammonium chloride) (PDMAC). UV-Vis absorbance and atomic force microscopy (AFM) topography data reveal a linear growth trend in film thickness that depends critically upon the assembly pH. At an assembly pH of 11.0 the multilayer was five times thicker compared to that assembled at pH 12.0. AFM topography images also show that the surface roughness of the films increases as the assembly pH decreases. 相似文献
6.
We present a field-theoretic Renormalization Group (RG) analysis of the statistical mechanics of long flexible, screened polyelectrolyte
chains (Debye-Hückel chains) in polar solvents where the screening length is of the order of the chain size. A systematic
analysis of the resulting field theory shows that the system is one with two length-scales requiring the calculation of scaling functions as well as exponents to fully describe its physical behaviour. This means that care
must be taken to understand the interplay of the length-scales. Using the RG we identify the relevant scaling variables and
explicitly calculate the scaling behaviour of the end-to-end distance for single chains. In addition we consider the many-chain
system and calculate the scaling behaviour of the osmotic pressure of a dilute solution of chains.
Received 16 December 1999 and Received in final form 13 December 2000 相似文献
7.
D. Langevin 《The European physical journal. E, Soft matter》2001,5(1):81-85
Studies of thin liquid films, made from semidilute polyelectrolyte solutions, are presented. The disjoining pressure variation
with film thickness exhibits oscillations, corresponding to film stratification. The oscillations become sharper as the polymer
concentration c increases, and disappear when salt is added. The period of the oscillations scales as c
-1/2. The observed stratification is related to the polymer network and the size of the steps to the mesh size ξ.
Received 25 April 2000 and Received in final form 3 October 2000 相似文献
8.
The sequential adsorption of oppositely charged polyelectrolytes (PE) occurs to be a powerful tool for obtaining various materials of precisely defined properties. The interfacial features of PE multilayer films are governed by the choice of polycation/polyanion pairs and the conditions of film formation. Additionally, the long time exposure to the conditions different than that encountered during formation usually affects polyelectrolyte multilayer structure.The wettability of heterogeneous surfaces produced by ‘layer-by-layer’ (LbL) adsorption of polyelectrolytes was investigated in this work. We focused on the influence of film treatment after deposition on wetting properties of obtained multilayers. The effect of the nature of the first layer was also studied. Apart from simple arrangements: (polyallylamine hydrochloride)/(polysodium 4-styrenesulfonate) (PAH/PSS) and (poly-l-lysine hydrobromide)/(poly-l-glutamic acid sodium salt) (PLL/PGA) more complicated structures were considered having as a first layer two types of polyethylene imines (PEI) of different molecular weight.Wetting properties of such polyelectrolyte films were determined experimentally by contact angle measurements using technique of direct image analysis of the shape of sessile drop. 相似文献
9.
A. Martin O. Rossier A. Buguin P. Auroy F. Brochard-Wyart 《The European physical journal. E, Soft matter》2000,3(4):337-341
We study theoretically the behavior of nanoscopic liquid films L (thickness e) intercalated between a solid S and a rubber R (elastic modulus μ). Thickness modulations involve a healing length , which results from a competition between elastic and disjoining pressure. With van der Waals interactions, , where a is a molecular size and h0 the rubber capillary length ( , interfacial tension). If the Hamaker constant of the intercalated liquid is negative, the film dewets by amplification of
peristaltic fluctuations (“spinodal dewetting”). The typical size of the contacts is predicted to scale like for films of thicknesses . The rise time of the fastest mode, predicted to scale like , should be very sensitive to the film thickness.
Received 11 February 2000 and Received in final form 22 May 2000 相似文献
10.
D. Sornette J.V. Andersen 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):353-357
We revisit a simple dynamical model of rupture in random media with long-range elasticity to test whether rupture can be seen
as a first-order or a critical transition. We find a clear scaling of the macroscopic modulus as a function of time-to-rupture
and of the amplitude of the disorder, which allows us to collapse neatly the numerical simulations over more than five decades
in time and more than one decade in disorder amplitude onto a single master curve. We thus conclude that, at least in this
model, dynamical rupture in systems with long-range elasticity is a genuine critical phenomenon occurring as soon as the disorder
is non-vanishing.
Received: 11 July 1997 / Revised: 6 November 1997 / Accepted: 10 November 1997 相似文献