RWTH Aachen University, Institute of Physical Chemistry, Landoltweg 2, 52074, Aachen, Germany.
Institut de Chimie Séparative de Marcoule, ICSM, CEA, CNRS, ENSCM, Univ Montpellier, Marcoule, France.
Angew Chem Int Ed Engl. 2023 Jan 16;62(3):e202210208. doi: 10.1002/anie.202210208. Epub 2022 Dec 13.
Nanometer-sized anions (nano-ions) like polyoxometalates and boron clusters exhibit so-called superchaotropic behavior, which describes their strong binding to hydrated non-ionic matter in water. We show here that nano-ions, at millimolar concentrations, dramatically enhance the viscosity and induce gelation of aqueous solutions of non-ionic cellulose ethers (CEs), a class of widely utilized polymers known for their thickening and gel-forming ability. These phenomena arise from an interplay of attractive forces and repulsive electrostatic forces between CE-chains upon nano-ion binding. The attractive forces manifest themselves as aggregation of CE-chains into a physically crosslinked polymer network (gel). In turn, the electrostatic repulsions hamper the viscosity increase and gelation. Superchaotropic nano-ion binding emerges as a novel and general physical crosslinking motif for CE-solutions and exceeds by far the conventional thickening effects of classical salts and ionic surfactants.
纳米尺寸的阴离子（纳米离子），如多金属氧酸盐和硼簇，表现出所谓的超亲溶行为，描述了它们在水中与水合非离子物质的强结合。我们在这里表明，纳米离子在毫摩尔浓度下，可显著提高水不溶性纤维素醚（CE）水溶液的粘度并诱导其凝胶化，CE 是一类广泛使用的聚合物，以其增稠和形成凝胶的能力而闻名。这些现象是由于纳米离子结合时 CE 链之间的吸引力和排斥静电之间的相互作用产生的。吸引力表现为 CE 链聚集形成物理交联的聚合物网络（凝胶）。反过来，静电排斥又阻碍了粘度的增加和凝胶的形成。超亲溶纳米离子结合成为 CE 溶液的一种新颖且通用的物理交联模式，远远超过了传统盐类和离子表面活性剂的增稠效果。
