Semidilute solution rheology of polyelectrolytes with no added salt

Krause, Wendy E.; Tan, Jessie; Colby, Ralph H.

doi:10.1002/(sici)1099-0488(19991215)37:24<3429::aid-polb5>3.0.co;2-e

Cited by 63 publications

(99 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, at the length scales smaller than the solution correlation length the strong electrostatic coupling between sections of the chain still persists and determines the characteristic relaxation time of these chain's sections. This dependence of the chain relaxation time is in a good qualitatively agreement with the experimental data by Colby's group 14,15,21,23 on the variety of the polyelectrolyte systems and is the main reason behind the famous Fuoss law for the concentration dependence of the polyelectrolyte solution viscosity.…”

Section: Discussionsupporting

confidence: 89%

Rouse Dynamics of Polyelectrolyte Solutions: Molecular Dynamics Study

et al. 2007

View full text Add to dashboard Cite

We performed molecular dynamics simulations of dilute and semidilute polyelectrolyte solutions without hydrodynamic interactions to study Rouse dynamics of polyelectrolytes. Polyelectrolyte solutions are modeled by an ensemble of bead-spring chains of charged Lennard-Jones particles with explicit counterions. The simulations were performed for partially and fully charged polymers with the number of monomers N ) 25-373. We show that the simulations of the Rouse dynamics give qualitatively similar results to the experimentally observed dynamics of polyelectrolyte solutions. Our simulations showed that the chain relaxation time depends nonmonotonically on polymer concentration. In dilute solutions, this relaxation time exhibits very strong dependence on the chain degree of polymerization, τ ∼ N 3 . The chain relaxation time decreases with increasing polymer concentration of dilute solutions. This decrease in the chain relaxation time is due to chain contraction induced by counterion condensation. In the semidilute solution regime the chain relaxation time decreases with polymer concentration as c -1/2 . In this concentration range the chain relaxation time follows the usual Rouse scaling dependence on the chain degree of polymerization, τ ∼ N 2 . At high polymer concentrations the chain relaxation time begins to increase with increasing polymer concentration. The crossover polymer concentration to the new scaling regime does not depend on the chain degree of polymerization, indicating that the increase in the chain relaxation time is due to the increase of the effective monomeric friction coefficient. The analysis of the spectrum and of the relaxation times of Rouse modes confirms the existence of the single correlation length , which describes both static and dynamic properties of semidilute solutions.

show abstract

Section: Discussionsupporting

confidence: 89%

Rouse Dynamics of Polyelectrolyte Solutions: Molecular Dynamics Study

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Recently, Krause et al [20] measured the PTCDAAg(111) distance to be ∼ 2.85Å, with an uncertainty of ±0.2Å. We expect a similar (or slightly larger) distance, of ∼ 3.0Å for the PTCDA-Au(111) system.…”

supporting

confidence: 51%

Dipole formation at metal/PTCDA interfaces: Role of the Charge Neutrality Level

Vázquez

Oszwałdowski²,

Pou³

et al. 2004

Europhys. Lett.

224

185

View full text Add to dashboard Cite

The formation of a metal/PTCDA (3, 4, 9, 10-perylenetetracarboxylic dianhydride) interface barrier is analyzed using weak chemisorption theory. The electronic structure of the uncoupled PTCDA molecule and of the metal surface is calculated. Then, the induced density of interface states is obtained as a function of these two electronic structures and the interaction between both systems. This induced density of states is found to be large enough (even if the metal/PTCDA interaction is weak) for the definition of a Charge Neutrality Level for PTCDA, located 2.45 eV above the highest occupied molecular orbital. We conclude that the metal/PTCDA interface molecular level alignment is due to the electrostatic dipole created by the charge transfer between the two solids.Electronic materials made of molecular films are a fast developing field, with many potential applications in organicbased devices. Designing new organic-based materials requires a detailed understanding of the different processes occurring in these devices. In particular, metal/organic and semiconductor/organic interface barriers play a decisive role [1,2]. However, the formation of barriers is not yet well understood.In the Schottky-Mott model of metal/organic interfaces, it is assumed that no interface dipole is formed at the junction, and that the position of molecular levels with respect to the metal Fermi level is defined by vacuum level alignment. This situation was disproved by Narioka et al.[3] who, using ultra-violet photoemission spectroscopy (UPS), found large interface dipoles (∼ 0.5 − 1.0eV ) at several metal/organic interfaces. Independent data by Hill et al.[4] confirmed this conclusion. Various mechanisms are believed to operate simultaneously at these interfaces, and several models have been advanced [1,2]. Metal-molecule chemical reaction has been seen to create interface gap states that pin the Fermi level [5], a situation that is analogous to that described by the Unified Defect Model proposed for inorganic semiconductor/metal interfaces [6]. Compression of the metal surface electronic tail by adsorbed molecules, leading to vacuum level interface shift (the "pillow" effect), has also been proposed as a general metal/organic interface mechanism [7,8,9].In this letter, we explore the first application to a metal/organic interface of the Induced Density of Interface (or virtual) States (IDIS) Model [10]. We study a metal/PTCDA (3, 4, 9, 10-perylenetetracarboxylic dianhydride) interface and analyze how the chemical interaction between the organic molecule and the metal creates an IDIS in the organic energy gap. Our calculations show that, although the chemical interaction is weak, the IDIS is large enough that a Charge Neutrality Level (CNL) of the organic molecule can be defined. Our results show that the interface Fermi level E F is pinned at the CNL, a situation similar to that described for the formation of Schottky barriers at conventional semiconductor/metal junctions.In this theoretical analysis, we study the metal/PTCDA interact...

show abstract

“…45 More significantly, the relaxation time t R of polyelectrolyte solutions also shows an initial increase and then an extended decrease (t R ∼ φ -1/2 ) as a function of concentration. 45,46 This effect is linked to the transition from rods to more compact coils as charge is screened at higher polymer concentrations. The total persistence length for a polyelectrolyte chain is the sum of an intrinsic and an electrostatic contribution: l p ) l p 0 + l p e .…”

Section: Q‚i(q)mentioning

confidence: 96%

Microstructure and Dynamics of Wormlike Micellar Solutions Formed by Mixing Cationic and Anionic Surfactants

2000

View full text Add to dashboard Cite

Small-angle neutron scattering (SANS) and rheology are used to probe the wormlike micelles formed in mixtures of a cationic (cetyl trimethylammonium tosylate, CTAT) and an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS). For a fixed composition of 97/3 CTAT/SDBS, the zero-shear viscosity η 0 initially increases rapidly with surfactant concentration, but decreases beyond an intermediate concentration φ max . The solutions show a scattering peak in SANS and the height of the scattering peak also exhibits a maximum around φ max . These results are interpreted in terms of a maximum in the linear micellar contour length L h at φ max , and suggest that the hydrodynamic and electrostatic correlation lengths reach an optimal ratio at this point. For a fixed total surfactant concentration, the viscosity η 0 also reaches a maximum at an intermediate SDBS fraction. The decrease in η 0 at high SDBS fractions is interpreted in terms of the polyelectrolyte nature of the micelles and the increased chain flexibility caused by the rising ionic strength of the solutions. An alternate possibility may involve a progression from linear to branched micelles with increasing SDBS content.

show abstract

Semidilute solution rheology of polyelectrolytes with no added salt

Cited by 63 publications

References 19 publications

Rouse Dynamics of Polyelectrolyte Solutions: Molecular Dynamics Study

Rouse Dynamics of Polyelectrolyte Solutions: Molecular Dynamics Study

Dipole formation at metal/PTCDA interfaces: Role of the Charge Neutrality Level

Microstructure and Dynamics of Wormlike Micellar Solutions Formed by Mixing Cationic and Anionic Surfactants

Contact Info

Product

Resources

About