Effect of counterion valence on the pH responsiveness of polyamidoamine dendrimer structure

Yun Liu, Lionel Porcar, Kunlun Hong, Chwen Yang Shew, Xin Li, Emily Liu, Paul D. Butler, Kenneth W. Herwig, Gregory S. Smith, Wei Ren Chen

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27 Scopus citations

Abstract

An accurate determination of the structure characteristics of protonated generation 5 polyamidoamine dendrimers in aqueous solution has been conducted by analyzing the small angle neutron scattering databased on a statistical mechanics model. In our investigation, the primary focus is to elucidate the effect of counterion valence on the counterion association and its impact on the intramolecular density profile within a dendrimer. In the range of our study for molecular protonation, a strong dependence of the structural properties of charged dendrimers on counterion valence is revealed. Our findings indicate that the association of a large amount of divalent counterions significantly reduces the effective charge of a dendrimer molecule. Surprisingly, no discernible transition of the density distribution profile is observed for the dendrimer charged by D2 SO4, as opposed to our previous observation of a pronounced transition in intramolecular density profile for the dendrimer charged by DCl. These findings may be understood from the thermodynamic processes of counterions.

Original languageEnglish
Article number124901
JournalJournal of Chemical Physics
Volume132
Issue number12
DOIs
StatePublished - 2010

Funding

We gratefully acknowledge the support from the LDRD Program (Project ID No. 05125 and 05272) of ORNL. The support of the NCNR NIST, U.S. DOC in providing the neutron research facilities supported under NSF Agreement No. DMR-0454672 is also acknowledged. Part of this research was carried out at CNMS ORNL sponsored by the SUFD BES, U.S. DOE. We also thank the support from the City University of New York PSC grants.

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