Biomedical subjects

Igor I Potemkin

Publications and source records attributed to Igor I Potemkin.

4 recordsLinked to original sources

PubMed2006

Why ionic liquids can possess extra solvent power.

We use the Flory-Huggins theory to demonstrate conditions of extra solvent power of ionic liquids. The short-range interactions between anions, cations, and molecules of the solute are taken into account. We find that solvent power of the ionic liquids is enhanced if non-Coulomb interactions between the anions and cations are repulsive. The mechanism responsible for the extra solvent power is related to the "shielding" of the anion-cation interactions by the molecules of the solute.

Letter↗

PubMed2005

Effect of low-molecular-weight salt on the nematic ordering in solutions of rodlike polyelectrolytes.

Nematic ordering is studied in solutions of rodlike macroions in the presence of monovalent salt ions. The correlation free energy of electrostatic interactions is calculated within the framework of the Debye-Hückel approach. The phase diagram of the system is obtained. We have shown that the addition of salt destroys the weakly ordered nematic phase which is stable at small polymer concentrations. On the other hand, the salt widens the region of the phase separation between the isotropic (or weakly ordered nematic) and the highly ordered nematic phases at high polymer concentrations. An explanation of these effects is proposed.

Journal Article↗

PubMed2004

Nematic ordering in dilute solutions of rodlike polyelectrolytes.

Quantitative theory of orientational behavior of rodlike polyelectrolytes in dilute solution is developed. We find that in salt-free solutions many-body Coulomb interactions between macro- and counterions favor nematic ordering. It is shown that the orientationally isotropic phase of the solution becomes unstable toward nematic ordering at polymer concentration smaller than the overlap concentration. Our predictions are consistent with experimental observations for synthetic polyelectrolytes poly(p-phenylene)sulfonates in aqueous solutions.

Journal Article↗

PubMed2002

Rodlike polyelectrolyte solutions: effect of the many-body Coulomb attraction of similarly charged molecules favoring weak nematic ordering at very small polymer concentration.

The correlation free energy of the many-body Coulomb interactions in the solution of rodlike polyelectrolytes with counterions is calculated. For this purpose a theory of the Debye-Hückel type, based on the density functional approach, is developed. We have shown that for all the analyzed regimes electrostatic interactions of similarly charged rods are attractive independent of their mutual orientation. Coexistence of weakly and highly ordered nematic phases at intermediate degrees of ionization of the molecules is predicted. It is shown that the electrostatic attractive forces favor liquid-crystalline ordering and stabilize a weakly ordered nematic phase at very small polymer concentrations. In other words, isotropic solutions of charged rods are in many cases intrinsically unstable with respect to orientational ordering.

Journal Article↗