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search.filters.applied.f.access: openAccess × DDC: 620 × Subject: Electric fields × WGL Institute: IPF ×

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Now showing 1 - 3 of 3
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    Charged polymers transport under applied electric fields in periodic channels
    (Basel : MDPI AG, 2013) Nedelcu, S.; Sommer, J.-U.
    By molecular dynamics simulations, we investigated the transport of charged polymers in applied electric fields in confining environments, which were straight cylinders of uniform or non-uniform diameter. In the simulations, the solvent was modeled explicitly and, also, the counterions and coions of added salt. The electrophoretic velocities of charged chains in relation to electrolyte friction, hydrodynamic effects due to the solvent, and surface friction were calculated. We found that the velocities were higher if counterions were moved away from the polymeric domain, which led to a decrease in hydrodynamic friction. The topology of the surface played a key role in retarding the motion of the polyelectrolyte and, even more so, in the presence of transverse electric fields. The present study showed that a possible way of improving separation resolution is by controlling the motion of counterions or electrolyte friction effects.
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    Counterion condensation and effective charge of PAMAM dendrimers
    (Basel : MDPI AG, 2011) Böhme, U.; Klenge, A.; Hänel, B.; Scheler, U.
    PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino groups which is monitored via the proton chemical shifts of the adjacent CH2 groups. The effective charge is determined from a combination of diffusion and electrophoresis NMR. The fraction of the charges, which are effective for the interaction with an external electric field or other charges, decreases with increasing generation (size) of the dendrimers.
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    Charge inversion effects in electrophoresis of polyelectrolytes in the presence of multivalent counterions and transversal electric fields
    (Basel : MDPI AG, 2014) Nedelcu, S.; Sommer, J.-U.
    By molecular dynamics simulations we investigate the transport of charged polymers in confinement, under externally applied electric fields, in straight cylinders of uniform diameter and in the presence of monovalent or multivalent counterions. The applied electric field has two components; a longitudinal component along the axis of the cylinder and a transversal component perpendicular to the cylinder axis. The direction of electrophoretic velocity depends on the polyelectrolyte length, valency of the counterions present in solution and transversal electric field value. A statistical model is put forward in order to explain these observations.