Polyelectrolyte electrophoresis and sedimentation of polymers : a mesoscale simulation study

In order to gain insight into sedimentation of polymers and polyelectrolyte electrophoresis in presence of hydrodynamic interactions, computer simulations (MD and MPCD) are applied. We investigate dynamical and conformational properties of the polymer chains by determining characteristic quantities like, e.g., mobility, diffusion coefficient, radius of gyration, and end-to-end distance. We obtain a detailed picture by varying chain length and strength of the external (gravitational or electric) field. In the electrophoresis study, we additionally vary the Coulomb interaction strength. As for sedimentation, we find that for weak gravitational fields the mobilities of small chains can be described within the Zimm model for polymers with excluded volume interactions. Above a critical chain length, as well as for larger gravitational fields, a completely different behavior is found. Furthermore, we observe conformations like coils, u-shape structures, and structures where the polymers form a coiled head region with a stretched tail. Obviously, the conformations are strongly affected by hydrodynamic interactions. In the electrophoresis study a matter of particular interest is to compare our results with experimental data. For a weak electric field which corresponds to the linear response regime and for an intermediate Coulomb interaction strength we find qualitative agreement of the electrophoretic mobility obtained in our simulations with the one measured in experiments. Here, the chain only exhibits rodlike conformations (which are not aligned in the electric field) although the polymer is completely flexible. At larger fields we observe a variety of conformational properties of the polyelectrolytes depending on chain length and Coulomb interaction. Strong electric fields in addition with weak to intermediate Coulomb interaction strengths lead to u-shape conformations which are the results of purely hydrodynamic interactions. Counterion condensation does virtually not take place. Strong Coulomb interactions and strong electric fields lead to perfectly elongated rods which orient parallel to the direction of the electric field: the electric field induces a charge asymmetry along the chain corresponding to a dipole which is then aligned by the field.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2008

Author dc:creator

• Frank, Sandra

Contributors dc:contributor

• Winkler, Roland G.

• info:eu-repo/classification/ddc/530
• Polyelektrolyt
• Elektrophorese
• Hydrodynamik
• Computersimulation
• Physik
• Mobilitaet
• Gegenionenkondensation
• polyelectrolyte
• electrophoresis
• hydrodynamics
• mesoscale computer simulation
• mobility
• counterion condensation

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-112770%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A50216