Molecular dynamics and neutron scattering study of the dependence of polyelectrolyte dendrimer conformation on counterion behavior

Chen, Wei-Ren; Do, Changwoo; Egami, T; Hong, Kunlun; Li, Xin; Liu, Emily; Liu, Yun; Porcar, L.; Smith, Gregory Scott; Smith, Sean C.; Wu, Bin

doi:10.1063/1.4742190

Molecular dynamics and neutron scattering study of the dependence of polyelectrolyte dendrimer conformation on counterion behavior

Journal Article · Wed Aug 01 00:00:00 EDT 2012 · The Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4742190· OSTI ID:1048155

^[1]; ^[1]; Egami, T ^[2]; ^[1]; Li, Xin ^[1]; Liu, Emily ^[3]; Liu, Yun ^[4]; Porcar, L. ^[4]; ^[1]; Smith, Sean C. ^[1]; Wu, Bin ^[1]

ORNL
University of Tennessee, Knoxville (UTK)
Rensselaer Polytechnic Institute (RPI)
National Institute of Standards and Technology (NIST)

Atomistic molecular dynamics (MD) simulations and contrast variation small angle neutron scattering (SANS) technique have been used to investigate the generation-5 (G5) polyelectrolyte polyamidoamine (PAMAM) starburst dendrimer with respect to its conformational dependence on counterion behavior at different levels of molecular charge. Satisfactory agreement is seen between the simulated results, such as the excess intra-dendrimer scattering length density (SLD) distribution and hydration level, and their experimental counterparts. The conformational evolution of charged dendrimer appears to be highly dependent on the association behavior of counterion. We explore the nature of the distribution of counterions around charged amines and qualitatively account for its sensitivity to the counterion valency on the difference of excess free energy. Moreover, via extending the concept of electrical double layer for compact charged colloids, we define an effective radius of charged dendrimer based on the spatial distribution of counterions in its vicinity. Within the same framework, the correlation between the strength of intra-dendrimer electrostatic repulsion and counterion valency and dynamics is also addressed.

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE

DOE Contract Number:: AC05-00OR22725

OSTI ID:: 1048155

Journal Information:: The Journal of Chemical Physics, Journal Name: The Journal of Chemical Physics Journal Issue: 137 Vol. 137; ISSN JCPSA6; ISSN 0021-9606

Country of Publication:: United States

Language:: English

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