Spatial distribution of intra-molecular water and polymeric components in polyelectrolyte dendrimers revealed by small angle scattering investigations.
An experimental scheme using contrast variation small angle neutron scattering technique is developed to investigate the structural characteristics of amine-terminated poly(amidoamine) dendrimers solutions. Using this methodology, we present the dependence of both the intra-dendrimer water and the polymer distribution on molecular protonation, which can be precisely adjusted by tuning the pH of the solution. Assuming spherical symmetry of the spatial arrangement of the constituent components of dendrimer, and that the atomic ratio of hydrogen-to-deuterium for the solvent residing within the cavities of dendrimer is identical to that for the solvent outside the dendrimer, the intra-dendrimer water distribution along the radial direction is determined. Our result clearly reveals an outward relocation of the peripheral groups, as well as enhanced intra-dendrimer hydration, upon increasing the molecular protonation and, therefore, allows the determination of segmental backfolding in a quantitative manner. The connection between these charge-induced structural changes and our recently observed progressively active segmental dynamics is also discussed.
Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Bin
B
Wu
Xin
X
Li
Changwoo
C
Do
Tae-Hwan
TH
Kim
Chwen-Yang
CY
Shew
Yun
Y
Liu
Jun
J
Yang
Kunlun
K
Hong
Lionel
L
Porcar
Chun-Yu
CY
Chen
Emily L
EL
Liu
Gregory S
GS
Smith
Kenneth W
KW
Herwig
Wei-Ren
WR
Chen