Article

Flexible Polyelectrolytes with Monovalent Salt

Physica A: Statistical Mechanics and its Applications (Impact Factor: 1.72). 07/2004; DOI: 10.1016/j.physa.2005.05.048
Source: arXiv

ABSTRACT We present a model for describing flexible polyelectrolytes in a good solvent a nd in the presence of monovalent salt . The molecule composed by $N$ monomers is characterized by the end to end distanc e $R_e=b (Z-1)^\gamma$ and the number of associated counterions $n$. At high tem peratures the polyelectrolyte behaves as a neutral polymer ($\gamma=0.588$). Dec reasing the temperature, the macromolecule changes from this extended configurat ion($\gamma=0.588$) to a stretched form ($\gamma\approx 1$). At even lower temp eratures, above the Manning condensation threshold, the polyelectrolyte collapse s ($\gamma\approx 0.3$). Our results show good agreement with simulations.

Full-text

Available from: Marcia Barbosa, Mar 21, 2015
0 Followers
 · 
63 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The properties of dilute solutions of regular polyampholytes in the presence of a low-molecularmass salt were studied by means of stochastic dynamics simulation. The number-average concentration of polymer units in solution did not exceed 0.038, a value that is below the coil overlap concentration at N= 1024. The effect of charge (valence) of ions of an added salt on the macromolecule size and distribution of the salt inside the polymer coil at different temperatures was considered. It was found that the condensation of salt ions over the temperature range examined (1 ≤T≤2ε/k B) takes place in the case of multiply charged systems of the (+4−4) or (+4−2) type. The maximal penetration of salt ions into the volume of the macromolecule was observed in the case of a (+2−2) salt.
    Polymer Science Series A 02/2008; 50(2):206-211. DOI:10.1134/S0965545X08020168 · 0.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The denaturation of the DNA is analyzed using an analytic model. The DNA molecules are described in the Primitive Model of Polyelectrolytes (PMP), where the polyelectrolyte molecules are cylinders with charged sites. We show that the DNA stabilization arises as the result of the competition between the electrostatic repulsion of the phosphate groups and the attractive forces of the H-bonds. We also show that the addition of salt in the system screens the electrostatic interactions and favors the double strand configuration.
    Physica A: Statistical Mechanics and its Applications 11/2014; 413:481–488. DOI:10.1016/j.physa.2014.06.059 · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We evaluate an approximate free energy for polyelectrolyte gels, including entropic effects due to flexibility of chains and electrostatic effects due to net charge of chains. The electrostatic terms depend on the binding fraction of ions m to the network and on the degree of swelling α of the chains. One term describes the interaction of the chains with the ionic solution and the other comes from the internal partition function of the macromolecules of the gel. The equilibrium values of m, α and the mixing parameter χ are obtained. This is also done for some experimental values of gel strength and volume fractions. The critical point for volume phase transitions is evaluated, and we find that the critical temperature increases as the charge on the chains increases, while the critical volume fraction of polymer decreases.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 06/2006; 281(1):184-189. DOI:10.1016/j.colsurfa.2006.02.037 · 2.35 Impact Factor