Schmid Philipp, Buchecker Thomas, Khoshsima Ali, Touraud Didier, Diat Olivier, Kunz Werner, Pfitzner Arno, Bauduin Pierre
Institute of Inorganic Chemistry, University of Regensburg, 93040 Regensburg, Germany; Institut de Chimie Séparative de Marcoule, ICSM, CEA, CNRS, ENSCM, Univ Montpellier, Marcoule, France.
School of Petroleum and Chemical Engineering, Hakim Sabzevari University, Sabzevar, Iran; Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany.
J Colloid Interface Sci. 2021 Apr;587:347-357. doi: 10.1016/j.jcis.2020.12.003. Epub 2020 Dec 7.
Nanometric ions, such as polyoxometalates (POMs) or ionic boron clusters, with low charge density have previously shown a strong propensity to bind to macrocycles and to adsorb to neutral surfaces: micellar, surfactant covered water-air and polymer surfaces. These association phenomena were shown to arise from a solvent-mediated effect called the (super-)chaotropic effect. We show here by combining cloud point (CP) measurements, scattering (SAXS/SANS) and spectroscopic techniques (NMR) that Keggin POMs: HSiWO (SiW) and HPWO (PW), induce the self-assembly of an organic solvent: dipropylene glycol n-propylether (CP), in water. The strong interaction between SiW/PW with CP leads to a drastic increase in the CP, and aqueous solubility, of CP, e.g. SiW enables reaching full water-CP co-miscibility at room temperature. At high POM concentrations, SiW leads to a continuous increase of the CP, forming SiW-[CP] complexes, whereas PW produces a decrease in the CP attributed to the formation of nearly "dry" spherical [PW][CP] colloids, with n ~ 4 and m ~ 30. At high CP/PW contents, the [PW][CP] colloids turn into large interconnected structures, delimiting two pseudo-phases: a PW-CP-rich phase and a water-rich phase. It is proposed that the stronger electrostatic repulsions between SiW (4-), compared to PW (3-), prevents the formation of mesoscopic colloids.
纳米离子，如多金属氧酸盐（POMs）或离子硼簇，由于其低电荷密度，此前已显示出与大环强烈结合并吸附到中性表面的倾向：胶束、表面活性剂覆盖的水-空气界面和聚合物表面。这些缔合现象被证明是由一种称为（超）离液效应的溶剂介导效应引起的。我们在此通过结合浊点（CP）测量、散射（SAXS/SANS）和光谱技术（NMR）表明，Keggin型多金属氧酸盐：HSiWO（SiW）和HPWO（PW），能在水中诱导有机溶剂：二丙二醇正丙醚（CP）的自组装。SiW/PW与CP之间的强相互作用导致CP以及CP在水中的溶解度急剧增加，例如SiW能使CP在室温下达到完全与水互溶。在高POM浓度下，SiW导致CP持续增加，形成SiW-[CP]复合物，而PW则导致CP降低，这归因于形成了近乎“干燥”的球形[PW][CP]胶体，其中n约为4，m约为30。在高CP/PW含量下，[PW][CP]胶体转变为大型相互连接的结构，界定出两个伪相：富含PW-CP的相和富含水的相。有人提出，与PW（3-）相比，SiW（4-）之间更强的静电排斥作用阻止了介观胶体的形成。
