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  • 1
    Electronic Resource
    Electronic Resource
    Conformation of weakly charged polyelectrolytes at a solid–liquid interface (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6873-6878 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption characteristics of polyelectrolyte chains on a plane surface are derived. The approach uses the mean-field arguments first developed by de Gennes [Rep. Prog. Phys. 32, 187 (1969)] and Richmond and Jones and Richmond [J. Chem. Soc. Faraday Trans. 73, 1062 (1977)] for the evaluation of the configuration probability of a neutral chain at an interface. Electrostatic interactions among monomers are treated through the linearized Poisson–Boltzmann equation. The treatment is restricted to dilute solutions and to weakly charged polyelectrolytes. Simply analytical expressions are derived for the concentration profile and the adsorption isotherm which are expressed in terms of two characteristic lengths L1 which characterizes the range of surface forces and L2, the Debye–Hückel length, which characterizes the range of electrical forces. Once these variables are fixed, it appears that the adsorption cannot exceed a critical value Γm which is tuned by the temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460267
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of bulk diffusion on the adsorption of hard spheres on a flat surface (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3813-3820 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Irreversible adsorption of hard spheres onto a solid surface is analyzed by using a generalization of the "random sequential adsorption'' (RSA) model: "diffusion random sequential adsorption'' (DRSA). In addition to the irreversible nature of the adsorption process and exclusion effects of the adsorbed configurations of hard spheres, the new model also considers the interactions between adsorbed particles and particles from the bulk, diffusing toward the surface. It is shown, in particular, that this affects the structure of adsorbed configurations for coverages different from the jamming limit coverage θ∞. Surprisingly, θ∞ appears to be identical for configurations generated by RSA and DRSA algorithms. Moreover, the structures of the configurations, as characterized by the radial distribution function g(r), are also identical at the jamming limit, whereas they differ for lower coverages. The coupling between the bulk diffusion process and the "adsorption process'' is also analyzed as a function of the coverage. New approximate boundary conditions at the interface for the adsorption–diffusion equations are derived and the adsorption rate is calculated for a particular example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462963
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  • 3
    Electronic Resource
    Electronic Resource
    Grafted polymers under the influence of external fields (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8142-8153 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure of grafted polymer "brushes'' may be profoundly modified by the action of "external fields''—local shifts in chemical potential due to, e.g., interfacial effects at the grafting surface. We discuss the strong-stretching limit of the self-consistent mean-field theory for a brush exposed to an arbitrary external potential, a simple scaling law for the brush height arises in the case where the external field pushes monomers towards the surface. In contrast, repulsive interactions can lead to "exclusion zones'' or regions from which polymer ends are repelled, leading to a breakdown of the simple scaling formula. We exactly solve the self-consistent theory of the brush in a repulsive square well where an exclusion zone always appears. Our results describe a brush in the case where a thin layer of one component of a binary solvent that is a worse solvent for the polymer than is the bulk mixture wets the grafting surface. We also discuss the effects of thermal fluctuations and chain polydispersity on our results, and estimate the effects of various interfacial phenomena on the brush structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465641
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal denaturation of an adsorbed fibrinogen layer studied by reflectometry (1987)
    s.l. : American Chemical Society
    Langmuir 3 (1987), S. 1128-1131 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00078a044
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  • 5
    Electronic Resource
    Electronic Resource
    Chain desorption from a semidilute polymer brush: A Monte Carlo simulation (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4379-4390 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We discuss the dynamic properties of a semidilute grafted polymer layer exposed to pure solvent. When the grafting energy of the head groups of the chains is finite, the chains desorb and are expelled from the layer. We combine Monte Carlo simulations using the bond fluctuation model to self-consistent mean field calculations and a scaling analysis. Chain desorption can be seen as a two step process. For strongly grafted polymers the limiting step is the desorption of the head group. The chain is then expelled by the osmotic pressure gradient. A chain cut off the wall is expelled at a constant velocity of its center of mass. The velocity decreases as the inverse of the molecular weight and increases with the grafting density. In the early stages of the expulsion the tension of the monomers close to the wall relaxes and the chain retracts. The retraction is independent of the molecular weight. Our most important result is that the desorption of the head group is a local process with a characteristic time independent of molecular weight. The desorption time increases exponentially with the grafting energy, it decreases as a power law of the grafting density. The exponent is close to 2 but the precise value is difficult to extract from the simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468410
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  • 6
    Electronic Resource
    Electronic Resource
    Bridging by adsorbed polymers between two surfaces (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 9181-9194 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We analyze the adsorption of flexible polymers between two parallel plates separated a distance 2l. We consider a semidilute polymer solution in contact with the two adsorbing walls and describe the statistics of bridges and loops. A detailed mean-field calculation allows us to obtain the size and density of bridges in two regimes: l(approximately-greater-than)ξ and l〈ξ, where ξ is the bulk correlation length, as well as the size of loop and train sequences. These results are compared with a scaling analysis performed in the spirit of the self-similar profile introduced by de Gennes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468448
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  • 7
    Electronic Resource
    Electronic Resource
    Adsorption Rate in the Convection-Diffusion Model (1994)
    s.l. : American Chemical Society
    Langmuir 10 (1994), S. 3898-3901 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00022a081
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  • 8
    Electronic Resource
    Electronic Resource
    Block copolymer adsorption in a selective solvent: a kinetic study (1990)
    s.l. : American Chemical Society
    Macromolecules 23 (1990), S. 5299-5311 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00228a001
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  • 9
    Electronic Resource
    Electronic Resource
    Characteristic time scales for the adsorption process for fibrinogen on silica (1992)
    s.l. : American Chemical Society
    Langmuir 8 (1992), S. 514-517 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00038a034
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamics of polymeric brushes: End exchange and bridging kinetics (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 1647-1658 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study some dynamical aspects of grafted polymer layers in a solvent. The structure of the brush is described in a θ solvent by the self-consistent mean field theory and in a good solvent using scaling laws. The Rouse–Zimm model including hydrodynamic interactions is used for the dynamic properties. A given chain end explores the entire thickness of a free grafted layer in a time Te proportional to the cube of the thickness. The exploration time is much larger than the Rouse time that characterizes the relaxation of the fluctuations of the chains conformations. In a θ-solvent we give a detailed study of the relaxation of the density of a few labeled chain ends towards its equilibrium value. The bridging kinetics between a grafting plate and a plate adsorbing the free ends is also discussed. When adsorption proceeds, an exclusion zone grows in the vicinity of the adsorbing plate. To cross the exclusion zone and adsorb, a chain end must overcome an energy barrier. The typical adsorption time is the first passage time through this barrier. Except in the very late stages where the fraction of chains η forming bridges saturates at its equilibrium value, the energy barrier against adsorption increases as a power law of η and the bridging fraction increases very slowly (logarithmically) with time. Both weak bridging where only a small fraction of chains form bridges and total bridging where all the chains form bridges are studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464281
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