DSM Ahead R&D BV, Advanced Chemical Engineering Solutions (ACES), P.O. Box 18, 6160 MD Geleen, The Netherlands; Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry & Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
DSM Ahead R&D BV, Advanced Chemical Engineering Solutions (ACES), P.O. Box 18, 6160 MD Geleen, The Netherlands.
J Colloid Interface Sci. 2017 Apr 1;491:141-150. doi: 10.1016/j.jcis.2016.12.021. Epub 2016 Dec 18.
Complexation between Methyl orange and polycations involves multiple interactions dictated by molecular structure, composition (D/P), pH and ionic strength. The effect of ionic strength is considered a generic effect. By step-wise construction of complexes, we expect to gain insight in the nature of interactions and whether displacement by competing ions is a generic effect.
We step-wise constructed complexes of methyl orange with two model polycations, whilst recording visible light spectra, size and electrophoretic mobility in buffered solution. MO organization was derived from discrete spectral changes, whereas complexes were described in terms of size and zeta-potential data. Spectral data were used to study the effect of competing ions, both potassium halides and polyanions, using a manual titration method.
Spectral and size data reveal a complex stoichiometry of D/P=2.2 and 4.6 for poly(ethylenimine hydrochloride)(PEI) and poly(di allyldimethyl amine hydrochloride) PDADMAC, respectively. Contrary to PEI-MO, the formation of PDADMAC-MO complexes is driven by hydrophobic rather than electrostatic interactions. Organization of PDADMAC-MO complexes also shows a strong dependency on the order of construction and polycation concentration. Displacement of MO by halides shows no effect of ion size for PEI, whereas Hofmeister series ordering was found for PDADMAC. The displacement by polyanions is shown to be charge-stoichiometric.
甲基橙与聚阳离子之间的络合作用涉及多种相互作用，这些相互作用受分子结构、组成（D/P）、pH 值和离子强度的影响。离子强度的影响被认为是一种普遍现象。通过逐步构建配合物，我们期望深入了解相互作用的本质，以及是否被竞争离子取代是一种普遍现象。
我们逐步构建了甲基橙与两种模型聚阳离子的配合物，同时在缓冲溶液中记录可见光光谱、大小和电泳迁移率。MO 组织来自离散的光谱变化，而配合物则根据大小和 ζ 电位数据来描述。使用手动滴定法研究了竞争离子（包括钾卤化物和聚阴离子）对光谱数据的影响。
光谱和大小数据显示，聚（盐酸乙基乙烯亚胺）（PEI）和聚（二烯丙基二甲基氯化铵盐酸盐）（PDADMAC）的配合物化学计量比分别为 D/P=2.2 和 4.6。与 PEI-MO 不同，PDADMAC-MO 配合物的形成是由疏水相互作用而非静电相互作用驱动的。PDADMAC-MO 配合物的组织也表现出对构建顺序和聚阳离子浓度的强烈依赖性。卤化物对 MO 的取代对 PEI 没有离子大小的影响，而对于 PDADMAC 则发现了 Hofmeister 序列排序。聚阴离子的取代被证明是电荷化学计量的。
