Synthesis And Characterization Of Metal-coordinated Polymeric Gels With Well-defined Structure

Intuitively, metal-coordinated polymeric gels (MCPGs) can be described as a subset of physically cross-linked polymers that form multi-dimensional networks, and where linkages between polymer backbones and/or functional groups of polymers are provided by reversible labile metal-ligand coordination interactions. MCPGs are observed to display particular photo-electro-magnetic, fascinating reversible and stimuli-responsive properties compared to those by covalent bonding. And MCPGs have received considerable attention from scientists due to their potential applications in fields of intelligent polymer materials.In this study, one-pot simultaneous metal-ligand coordination chemistry and CuAAC reactions were investigated to prepare stimuli-responsive MCPGs by a mixture of Terpy-φ-CH2C=CH and PEG45(N3)2. The MCPGs were based on PEG, and "click" (1,2,3-triazole rings) and terpyridine ligands in their main chains were served as ligands for chelating metal ions, suggesting that a three-dimensional network structure was formed by the connection between ligands and copper ions based on coordinative bonds. The switch from Cu+-MCPGs to the oxidized state, Cu2+-MCPGs, through a slow oxidation process (oxidation from Cu+ to Cu2+ occurs through simple exposure to ambient oxygen) was demonstrated. Comparison of their corresponding emission and absorption properties, and mechanical properties was also carried out. The subsequent click chemistry reaction catalyzed by rare earth metals of (PEG11(N3))m and Terpy-φ-CH2C=CH gave rise to RE-MCPGs. Chemical structures of compounds were characterized by 1H NMR and FT-IR. The properties of the MCPGs were characterized by UV-Vis, SEM, TGA, DSC, fluorescence, rheological behavior and ionic conductivity test measurements and so on.Conventional methods of synthesis of MCPGs require multiple reactions and post-processing operations, which are very complicated. Then a novel strategy to synthesize MCPGs via one-pot CuAAC and non-covalent metal coordination chemistry is demonstrated due to its simplicity, high efficiency and high resource utilization. Click chemistry reaction system catalyzed by rare earth metals, which reduces high valence rare earth metal ions into the low valence state caused by free radicals generated through using free radical initiators at a certain temperature and catalyzes click reaction of acetylenic and azido compounds simultaneously. It has spatio-temporal controllability and overcomes shortcomings of gel crosslinking network structure prepared by CuAAC. Click chemistry reaction system catalyzed by rare earth metals can synthesize RE-MCPGs with certain strength and functionalities. It was found that the bridging metal complexes in MCPGs could not only act as branching or crosslinking sites within the three-dimensional polymer networks but could also bestow special properties to the final gels, such as stimuli-responsive and thixotropic features.