Diffusion and interaction in gels and solution. 5. Nonionic micellar systems

Johansson, Lennart; Hedberg, Pia; Loefroth, Jan Erik

doi:10.1021/j100105a036

Cited by 31 publications

(48 citation statements)

References 6 publications

(10 reference statements)

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“…The decrease of D compared to the polymer-free system is due to obstruction by the polymer network and is in good agreement with the predictions of Johansson et al35 A similar concentration independence of D/Do was also observed for Cl2E8 micelles in a polysaccharide gel. 36 In the case of 3C18, significantly lower values of D/Do are obtained, demonstrating the association between the polymer and surfactant micelles. At lower surfactant concentrations, DIDO decreases with increasing concentration.…”

Section: Resultsmentioning

confidence: 90%

Polyelectrolyte association to micelles and bilayers

Iliopoulos¹,

Olsson²

1994

J. Phys. Chem.

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W e have investigated the association of hydrophobically modified poly(sodium acrylate) (HMPA) to micelles and bilayers of nonionic surfactant. The H M P A bears octadecyl chains randomly anchored on 1 or 3 mol 5% of the monomer units, and the surfactant is pentaethylene glycol dodecycl ether ( C I~E S ) or octaethylene glycol dodecyl ether (C12Eg). The H M P A was introduced in small amounts to the micellar and lamellar phases of the binary nonionic surfactant/water system. The association of H M P A with the nonionic surfactant aggregate is due to the hydrophobic alkyl chains of the polymer that dissolve in the surfactant film. This association behavior has a large impact on the rheological properties of the aqueous HMPA-nonionic micelles mixtures. Moreover, the bonding of the surfactant on the polymer induces a pronounced decrease of the micellar mobility as is evident from molecular self-diffusion measurements. Small amounts of HMPA dramatically increase the stability of the micellar phase. The change in phase behavior is similar to that obtained by adding small amounts of ionic surfactant to the surfactant film. Adding H M P A to the water/C12Es lamellar phase results in a strong decrease in turbidity, indicating a crossover from a dominating undulation to a dominating electrostatic repulsion between bilayers.

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Section: Resultsmentioning

confidence: 90%

Polyelectrolyte association to micelles and bilayers

Iliopoulos¹,

Olsson²

1994

J. Phys. Chem.

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“…The results obtained with 10 mM added 1 : 1 electrolyte at different polymer volume fractions are given in Table I. Thesevalues were then used in thesimulations tocompute the force in the equation of motion (see eqs [1][2][3][4].…”

Section: Ar = S ( a T ) + -F(r)mentioning

confidence: 99%

Diffusion and interaction in gels and solutions. 6. Charged systems

Johansson¹,

Skantze²,

Loefroth³

1993

J. Phys. Chem.

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Results are presented from Brownian dynamics simulations and from experimental measurements of selfdiffusion coefficients of monovalent ions in systems of oppositely charged polymers. The simulations were carried out in ordered and in random polyion systems. The ordered systems consisted of parallel straight chains on a square lattice, while in the other systems the straight polymer chains were randomly oriented. At low polymer concentrations there was good agreement between the results obtained in both types of systems. However, when the polyion concentration was increased, the ion diffusion was slower in the random than in the ordered systems. It is suggested that the observed results emanate from the distribution of interpolyion distances and the relative orientation of the chains present in the random systems. The interpretation is based on the transport in the bulk between the polyions as the rate-limiting process. The simulation data are in qualitative agreement with the experimental results. However, the experimental results also emphasize the importance of steric obstruction, which can be the dominant effect for large ions and in concentrated polyelectrolyte systems.

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“…Since their approach was based on the key concept of the distribution of “influence cylinders” introduced by Ogston, the approximation of D e is henceforth referred to as the Ogston approximation. To test the predictive capacity of their theory, Johansson and Löfroth [19] carried out hard-sphere Brownian-motion simulations, in which the diffusing particles were hard spheres and the fibers were considered to hinder the diffusion of the particles. Although hydrodynamic effects were not taken into account in their simulations, the results were shown to be in excellent agreement with experimental data and theoretical predictions for a wide range of particle sizes [19].…”

Section: Introductionmentioning

confidence: 99%

Quantitative characterization of the microstructure and transport properties of biopolymer networks

Jiao

Torquato

2012

Phys. Biol.

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Biopolymer networks are of fundamental importance to many biological processes in normal and tumorous tissues. In this paper, we employ the panoply of theoretical and simulation techniques developed for characterizing heterogeneous materials to quantify the microstructure and effective diffusive transport properties (diffusion coefficient De and mean survival time τ) of collagen type I networks at various collagen concentrations. In particular, we compute the pore-size probability density function P(δ) for the networks and present a variety of analytical estimates of the effective diffusion coefficient De for finite-sized diffusing particles, including the low-density approximation, the Ogston approximation, and the Torquato approximation. The Hashin-Strikman upper bound on the effective diffusion coefficient De and the pore-size lower bound on the mean survival time τ are used as benchmarks to test our analytical approximations and numerical results. Moreover, we generalize the efficient first-passage-time techniques for Brownian-motion simulations in suspensions of spheres to the case of fiber networks and compute the associated effective diffusion coefficient De as well as the mean survival time τ, which is related to nuclear magnetic resonance (NMR) relaxation times. Our numerical results for De are in excellent agreement with analytical results for simple network microstructures, such as periodic arrays of parallel cylinders. Specifically, the Torquato approximation provides the most accurate estimates of De for all collagen concentrations among all of the analytical approximations we consider. We formulate a universal curve for τ for the networks at different collagen concentrations, extending the work of Yeong and Torquato [J. Chem. Phys. 106, 8814 (1997)]. We apply rigorous cross-property relations to estimate the effective bulk modulus of collagen networks from a knowledge of the effective diffusion coefficient computed here. The use of cross-property relations to link other physical properties to the transport properties of collagen networks is also discussed.

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Diffusion and interaction in gels and solution. 5. Nonionic micellar systems

Cited by 31 publications

References 6 publications

Polyelectrolyte association to micelles and bilayers

Polyelectrolyte association to micelles and bilayers

Diffusion and interaction in gels and solutions. 6. Charged systems

Quantitative characterization of the microstructure and transport properties of biopolymer networks

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