Ionic Soft Condensed Matters by
  Molecular Dynamics Simulations
We frequently encounter soft condensed matters, which appear as daily
products (gelatin, paint, etc.) and the constituents of living objects including
proteins and the DNA. The soft condensed matters represent polymers,
gels and colloidal solutions.

Here we introduce our recent studies of "ionic soft condensed matters",
the characters (structures and functions) of which are highly influenced by
strong electrostatic forces.

Electrophoresis of a charge inverted macroion  In these ionic materials,
 
the net electrostatic energy
 
that brings forth structure
 exceeds thermal energy

 that tends to destroy the
 structure about several
 times
at room temperature.
 Interestingly, even if the
 material is electrically
neutral, the attraction force overcomes the repulsive force since the positive
and negative ions recognize each other and have the tendency of forming
ion pairs.

Figure: A charge inverted macroion, (a) All ions, (b) the blowup of the vicinity
of the macroion are displayed. The macroion is a large red sphere, counterions
and coions are light and dark blue spheres, respectively - Euro.Phys.J., E (2002).

The ionic soft condensed matters belong to "strongly coupled Coulomb
system". However, because of the electrostatic energy dominance over
thermal energy by only several times,
the softness (or stiffness) of these
materials can be controlled by environmental conditions
such as the
amount of salt (ionic strength), pH (concentration of hydrogen ions).
We can make good use of these properties in applications to daily
products. It might be the case with biochemical processes including
DNA and proteins to enable flexible structure changes for storage and
reproduction of themselves at the room temperature. With this regard,
the ionic soft condensed matters are very attractive and have wide
range of physical and chemical applications. For example, the charge
inversion phenomenon, described in the next section, is expected to be
used in
gene therapy for delivery of negatively charged DNA to living
cells having negative electrostatic potentials.


1.Charge Inversion of a Macroion in Solvent

2.Electrolyte (Charged) Polymers - Polyampholyte

3.DNA in Nanopore

4. Microwave Heating of Water and Ice

Movie: Molecular Dynamics Simulation of Charge Inversion


 Research Purpose and Results   Home