Coordination Polymers Based on Amphiphilic Oligomeric Silsesquioxanes and Transition Metal Ions (Co2+, Ni2+): Structure and Stimuli-Responsive Properties

Synthesis, structural organization, thermal, and magnetic properties of coordination polymers (OSS-polymer-Me) based on amphiphilic oligomeric silsesquioxanes (OSS) and transition metal ions (Co2+, Ni2+) are reported. The initial amphiphilic OSS containing various ratios of n-octadecylurethane and carboxyl groups (OSS-C18H37-x-COOH-y) are characterized with two types of ordered phases. The first one is a supramolecular structure stabilized by hydrogen bonds and characterized with a specific endothermic transition on differential scanning calorimetry thermograms (T-m1). The second one is presented by crystalline domains of aliphatic chains with a melting transition peak (T-m2). Inclusion of metals has no effect on the magnitude of T-m2 while leading to a decrease in the value of the T-m1 in comparison to the same compounds without metal. Being located in the nodes of the irregular network structure of OSS-polymer-Me, metal ions form approximate to 2 nm clusters, which connect multifunctional molecules of OSS-C18H37-x-COOH-y in a supramolecular system similar to disordered metal-organic framework. The OSS-polymer-Me nanocomposites display superparamagnetic properties determined by an adaptive behavior of the intermolecular network. The latter can be modified by the application of an external magnetic field and/or moderate heat.