Article

Counterion Association and Structural Conformation Change of Charged PAMAM Dendrimer in Aqueous Solutions Revealed by Small Angle Neutron Scattering

  1. Lionel Porcar1,
  2. Yun Liu2,3,
  3. Kunlun Hong4,
  4. Paul D. Butler3,
  5. E-Wen Huang5,
  6. Wei-Ren Chen6,*

Article first published online: 26 MAY 2009

DOI: 10.1002/masy.200950511

Issue

Macromolecular Symposia

Macromolecular Symposia

Special Issue: Polymers at Frontiers of Science and Technology – MACRO 2008 –

Volume 279, Issue 1, pages 65–71, May 2009

Additional Information

How to Cite

Porcar, L., Liu, Y., Hong, K., Butler, P. D., Huang, E.-W. and Chen, W.-R. (2009), Counterion Association and Structural Conformation Change of Charged PAMAM Dendrimer in Aqueous Solutions Revealed by Small Angle Neutron Scattering. Macromol. Symp., 279: 65–71. doi: 10.1002/masy.200950511

Author Information

  1. 1

    Institut Laue-Langevin, B.P. 156, F-38042 Grenoble CEDEX 9, France

  2. 2

    The NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6100, USA

  3. 3

    Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA

  4. 4

    The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA

  5. 5

    Department of Materials Science and Engineering, the University of Tennessee, Knoxville, TN 37996-2200, USA

  6. 6

    Neutron Scattering Science Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA

*Neutron Scattering Science Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA. Fax: (865) 574-6080.

Publication History

  1. Issue published online: 26 MAY 2009
  2. Article first published online: 26 MAY 2009

Funded by

  • Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy

SEARCH

SEARCH BY CITATION

ARTICLE TOOLS

Get PDF (235K)

Keywords:

  • counterion;
  • ornstein-zernike equation;
  • polyamidoamine dendrimers;
  • small angle neutron scattering

Abstract

Our previous study of the structure change of poly(amidoamine) starburst dendrimers (PAMAM) dendrimer of generation 5 (G5) have demonstrated that although the overall molecular size is practically unaffected by increasing DCl concentration, a configurational transformation, from a diffusive density profile to a more uniform density distribution, is clearly observed. In the current paper, the focus is placed on understanding the effect of counterion identity on the inter-molecular structure and the conformational properties by studying the effect due to DBr using small angle neutron scattering (SANS) and integral equation theory. While the overall molecular size is found to be essentially unaffected by the change in the pD of solutions, it is surprising that the intra-molecular configurational transformation is not observed when DBr is used. The overall effective charge of a dendrimer is nearly the same for α < 1, independent of the type of acids. However, when α > 1, the effect of counterion identity becomes significant, the effective charge carried by a charged G5 PAPAM protonated by DBr becomes smaller than that of solutions with DCl. As a consequence, a counterion identity dependence of counterion association is revealed: Under the same level of molecular protonation, the specific counterion association, which is defined as the ratio of bound chloride anions to positively charged amines per molecule, is larger for the G5 PAMAM dendrimer charged by DBr than the one by DCl.

Get PDF (235K)