Charged dendrimers under the action of AC electric fields: Breathing characteristics of molecular size, polarizations, and ion distributions

AK Das and PY Hsiao, JOURNAL OF CHEMICAL PHYSICS, 142, 084902 (2015).

DOI: 10.1063/1.4908563

Langevin dynamics simulations are performed to study the response of charged dendrimers in alternating current electric fields in 3:1 salt solutions. Time evolutions of molecular size show breathing characteristics which take saw-tooth-like patterns in square-wave electric fields and undulated sine-function ones in sine-wave fields. Detailed study reveals how the dendrimer and condensed ions oscillate in the electric fields, which result in polarization of the molecule. To effect a significant deformation of the dendrimer, the applied field amplitude must be larger than some critical strength E-crit and the field frequency smaller than a threshold f(crit). The response behavior is characterized by two relaxation times in square-wave fields, both of which decrease linearly with the strong field strength larger than E-crit. In sine-wave fields, the molecular size exhibits interesting hysteretic behavior in plotting the curves with the field variation. A Maxwell-Wagner type polarization theory is derived and proved by simulations, which connects f(crit) with the strength of the applied electric field. (C) 2015 AIP Publishing LLC.

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