Charged dendrimers under the action of AC electric fields: breathing characteristics of molecular size, polarizations, and ion distributions.
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 Ecrit and the field frequency smaller than a threshold fcrit. 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 Ecrit. 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 fcrit with the strength of the applied electric field.
Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan.
Ashok K
AK
Das
Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan.
Pai-Yi
PY
Hsiao