Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
J Phys Condens Matter. 2012 Feb 15;24(6):064116. doi: 10.1088/0953-8984/24/6/064116. Epub 2012 Jan 25.
Polyamidoamine (PAMAM) dendrimers and their charged state in deuterium oxide have been investigated with proton pulsed field gradient diffusion nuclear magnetic resonance (PFG-NMR) and small-angle neutron scattering (SANS) techniques. NMR measurements suggest that significant variation of the hydrodynamic radius, calculated by the Stokes-Einstein relation with appropriate surface conditions, is observed upon increasing the molecular protonation. However, a comparative SANS experiment indicates little dependence of the dendrimer global size, in terms of its radius of gyration, on molecular protonation. The inconsistency indicates the necessity of incorporating the effect of molecular interface modification and molecular porosity provided by dressed counterions, when dynamical measurements are used for the determination of the structural characteristics of ionic soft colloids even in dilute suspensions.
聚酰胺-胺（PAMAM）树状大分子及其在重水中的带电状态已通过质子脉冲梯度扩散核磁共振（PFG-NMR）和小角中子散射（SANS）技术进行了研究。NMR 测量表明，随着分子质子化程度的增加，通过适当的表面条件用 Stokes-Einstein 关系计算得到的流体力学半径会发生显著变化。然而，比较 SANS 实验表明，树状大分子的整体尺寸（以回转半径表示）几乎不受分子质子化的影响。这种不一致表明，在使用动力学测量来确定离子软胶体的结构特征时，即使在稀溶液中，也需要考虑分子界面修饰和由“穿隧”抗衡离子提供的分子多孔性的影响。
