Construction And Properties Of Supramolecular Polymers Based On Host–guest And Metal–ligand Interactions

Supramolecular chemistry is the chemistry of the intermolecular bond, covering the structures and functions of the entities formed by association of two or more chemical species. Large aggregates, constructed by linking monomer building blocks together via non-covalent interactions with polymer properties, are regarded as supramolecular polymers. Supramolecular polymers, polymeric systems beyond the molecule, have attracted more and more attention from scientists due to their applications in various ?elds, including stimuli-responsive materials, healable materials, and drug delivery. In recent years, metal–ligand interactions have been widely used in supramolecular polymer systems due to their highly directional and stable characteristics and strong tunable coordination binding abilities. This dissertation focuses on constructing a stimuli-responsive supramolecular polymer network by the orthogonal assembly of metal–ligand interactions and other non-covalent interactions. This dissertation comprise two parts.In the first part, we designed and synthesized a low molecular weight monomer by linking DB24C8 with two terpyridine units at ends. This low molecular weight monomer can form linear supramolecular polymer after the addition of the metal ligand Zn(OTf)2. By the continuous addition of bisammonium cross-linker, a supramolecular polymer network was obtained. The conversion between the linear supramolecular polymer and supramolecular polymer network can be realized by the destruction and reconstruction of the interactions between DB24C8 and DBAS via a change in pH. Moreover, the supramolecular polymer can also be directly converted into monomer by the addition of 1,4,7,10-tetraazacyclododecane(cyclen), which would destroy the interactions between terpyridine and Zn2+.In the second part, we constructed a multiple stimuli-responsive self-healing supramolecular polymer gel network formed by multiple orthogonal interactions, including host–guest interactions between DB24C8 and DBAS, metal–ligand coordination interactions between terpyridine and Zn(OTf)2, and between 1,2,3-triazole and PdCl2(PhCN)2. The topological structure of the supramolecular network can be regulated to main-chain linear supramolecular polymer and to dimeric complex by different stimuli. Moreover, supramolecular polymer gel was formed when the concentration was above 120 mg m L-1. The gel not only showed multiple-stimuli responsiveness such as temperature, pH, and competitive ligands but also exhibits self-healing properties because the formation of the gel network is totally based on reversible non-covalent interactions. The study of multiple responsiveness and self-healing of supramolecular polymer gels from low-molecular-weight monomers will shed light on the study of hierarchical assemblies based on multiple orthogonal interactions to work as advanced smart materials.