Studies Of Supramolecular Polymers And Supramolecular Gels Based On Crown Ethers

As an important part of supramolecualr assemblies, supramolecular polymer is a kind of dynamical polymeric structures. Various of noncovalent interactions, such as host-guest interactions, hydrogen bonds and metal coordination, have been widely introduced to prepare supramolecular polymers. Crown ethers, as the first generation of supramolecular hosts, have been widely used as building blocks to construct different functional assemblies with organic guest molecules. In this dissertation, we focus on the preparation of supramolecular polymers and supramolecular gels from low molecular weight monomers via the crown ether-based recognition motifs.In the first part, we designed and synthesized a supramolecular polymer and a supramolecular polymer gel. Based on the DB24C8/DBA recognition motif, we designed a AB-type monomer. This monomer would self-assemble to linear supramolecular polymes, and we also observed three-dimensional network from SEM experiments. By incorporating solvent molecules to3D network, supramolecular polymers could form supramolecular polymer gels. We also utilized the reversible complexation between DB24C8and DBA units to realize the gel-sol and sol-gel transitions.In the second part, we designed and synthesized a supramolecular polymer blend containing two diffenernt supramolecular polymers through self-sorting organization of two heteroditopic monomers. Due to the self-sorting organization, two heteroditopic monomers self-assembled to two different linear supramolecular polymers totally depending on their own host-guest interactions. This supramolecular polymer blend presented evidence that the self-sorting process not only takes place in solution, but also occurs in the gelation process and in the solid state. Considerating the phase separation both in macro-and micro-view in the supramolecualr polymer blend, we further tried to control the phase separation by self-sorting organization. We can effectively control the phase separation by the addition of low molecular weight linkers.In the third part, we reported a crown ether-appended super gelator with excellent gelation properties and multiple-stimulus responsive properties. We found this super-gelator can gelate almost all common organic solvents at relative low concentrations. This super gelator could gel acetonitrile at room temperature to form a transparent gel and the critical gelation concentration is0.06wt%. And the gel was stable under common conditions and had the ability of shape-persistent. This super gelator has one crown ether moiety (dibenzo-24-crown-8, DB24C8) and one organic ammonium salt unit, hence the corresponding supramolecular gel would be highly sensitive to many external stimuli, such as organic salts, acid/base and anions.In the forth part, we designed and synthesized two [2]rotaxanes based on pillar[5]arene/alkane recognition motif. Considering that the formation of the related pseudorotaxane-type threaded structure intermediates during the preparation of these [2]rotaxanes were mainly driven by weak C-H…π interactions, their yields (35%and20%) are reasonable. Furthermore, we showed that3,5-dinitrophenyl group and3,5-bis(trifluoromethyl)phenyl group are big enough to work as stoppers for DPPillar[5]arene. Considering the easy availability of pillar[5]arenes, alkane derivative rod components, and these stoppers, the convenient synthetic route, and the elegant mechanically interlocked structure, this kind of [2]rotaxanes will be widely used in the construction of novel fascinating supramolecular structures including molecular machines, molecular devices and supramolecular polymers.