Eghtesadi Seyed Ali, Haso Fadi, Kashfipour Marjan Alsadat, Lillard Robert Scott, Liu Tianbo
Department of Polymer Science, University of Akron, Akron, Ohio 44325 (USA) http://gozips.uakron.edu/∼tliu/
Department of Chemical and Biomolecular Engineering, University of Akron, Akron, Ohio 44325 (USA).
Chemistry. 2015 Dec 14;21(51):18623-30. doi: 10.1002/chem.201502852. Epub 2015 Nov 9.
The self-assembly of semiglobular, positively charged poly(propyleneimine) (PPI) dendrimers with small monovalent counterions (e.g., Cl(-)) in water/acetone mixtures was investigated. We showed that PPI dendrimers can assemble into hollow, spherical, single-layered blackberry-type structures mediated by the presence of monovalent counterions. The effects on the assembly of changing the solvent polarity and adjusting the pH were further investigated to confirm the presence of electrostatic interactions and hydrogen bonding as the driving forces. Results showed that PPI dendrimers form stable, hollow spheres in 5-20% v/v acetone/water and that the size of the spheres decreases monotonically as the solvent polarity and/or the charge on the dendrimers (i.e., lower solution pH) increases. This is the first example to show that small monovalent counterions can trigger attraction among PPI dendrimers (or broadly defined polyelectrolytes) that is strong enough to bring them together to form large, stable supramolecular assemblies, which indicates that these organic macroions have similar solution behavior to more-well-defined inorganic molecular macroions.
研究了半球状带正电的聚亚丙基亚胺（PPI）树枝状大分子与小的单价抗衡离子（如Cl(-)）在水/丙酮混合物中的自组装过程。我们发现，在单价抗衡离子的作用下，PPI树枝状大分子能够组装成中空的、球形的、单层的黑莓型结构。进一步研究了改变溶剂极性和调节pH值对组装的影响，以确认静电相互作用和氢键作为驱动力的存在。结果表明，PPI树枝状大分子在5-20% v/v的丙酮/水体系中形成稳定的中空球体，并且随着溶剂极性和/或树枝状大分子上的电荷（即较低的溶液pH值）增加，球体尺寸单调减小。这是首个表明小的单价抗衡离子能够引发PPI树枝状大分子（或广义定义的聚电解质）之间的吸引力，且该吸引力足以使它们聚集在一起形成大的、稳定的超分子聚集体的例子，这表明这些有机大离子与定义更明确的无机分子大离子具有相似的溶液行为。
