Ion-Specific Effects of Divalent Ions on the Structure of Polyelectrolyte Brushes.
Ion-Specific Effects of Divalent Ions on the Structure of Polyelectrolyte Brushes.
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DOI：
10.1021/acs.langmuir.9b01984
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
Xin Xu;Dean Mastropietro;M. Ruths;M. Tirrell;Jing Yu
中科院分区：
文献类型：
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作者：
Xin Xu;Dean Mastropietro;M. Ruths;M. Tirrell;Jing Yu
聚电解质电刷由一端高密度附着在表面的带电聚合物链组成。它们与许多实际应用有关，从生物传感器到药物输送到胶体稳定性。它们的结构和功能会受到溶液环境中多价反离子的显著影响。在这项工作中，使用表面力仪（SFA）和原子力显微镜（AFM）研究了三种碱土二价阳离子Mg2+， Ca2+和Ba2+对粘接在云母和氧化硅表面的聚苯乙烯磺酸钠（PSS）刷结构的影响。虽然所有这些离子都引起PSS刷高度的显着收缩，但观察到强烈的离子特异性效应。Mg2+和Ca2+引起均匀收缩；Ba2+导致了钉状胶束状的不均匀结构。等温滴定量热法（ITC）表明，这种离子特异性主要是由磺酸基与二价阳离子之间的结合能差异引起的。考虑到二价阳离子在工业过程、自然环境和生物系统中的丰度，了解二价反离子的强离子特异性效应对涉及聚电解质的理论研究和各种应用具有重要意义。
Polyelectrolyte brushes consist of charged polymer chains attached with one end to a surface at high densities. They are relevant for many practical applications ranging from biosensors to drug delivery to colloidal stability. Their structure and functionality can be dramatically influenced by multivalent counterions in the solution environment. In this work, the surface forces apparatus (SFA) and atomic force microscopy (AFM) were used to investigate the effect of three alkaline earth divalent cations, Mg2+, Ca2+, and Ba2+, on the structure of polystyrene sulfonate (PSS) brushes tethered to mica and silicon oxide surfaces. While all these ions caused significant shrinkage of the height of the PSS brushes, strong ion-specific effects were observed. Mg2+ and Ca2+ caused homogeneous shrinkage; Ba2+ led to pinned-micelle like inhomogeneous structures. Isothermal titration calorimetry (ITC) demonstrated that this ion specificity was mainly caused by the difference in binding energy between sulfonate groups and the divalent cations. Considering the abundance of divalent cations in industrial processes, natural environments, and biological systems, the understanding of strong ion-specific effects of divalent counterions is of great importance for theoretical studies and various applications involving polyelectrolytes.