The NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6100, USA.
J Chem Phys. 2010 Mar 28;132(12):124901. doi: 10.1063/1.3358349.
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 D(2)SO(4), 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.
通过基于统计力学模型分析小角中子散射数据，准确确定了质子化的第 5 代聚酰胺-胺树枝状大分子在水溶液中的结构特征。在我们的研究中，主要关注的是阐明抗衡离子价对抗衡离子缔合的影响及其对树枝状大分子内部分子密度分布的影响。在我们研究的分子质子化范围内，发现带电荷的树枝状大分子的结构性质强烈依赖于抗衡离子价。我们的研究结果表明，大量二价抗衡离子的缔合显著降低了树枝状大分子分子的有效电荷。令人惊讶的是，对于由 D(2)SO(4)带电荷的树枝状大分子，没有观察到密度分布轮廓的明显转变，而对于由 DCl 带电荷的树枝状大分子，我们之前观察到了分子内密度分布轮廓的明显转变。这些发现可以从抗衡离子的热力学过程来理解。
