| The development of supramolecular chemistry makes it possible to utilize small units to obtain high-molecular-weight aggregates with advanced architectures and unique functions via various noncovalent interactions. Among various noncovalent interactions used in the construction of supramolecular polymers, host-guest complexation and metal-ligand coordination are two main classes of noncovalent interactions and have been studied widely. Host-guest interactions endow supramolecular polymers with inherent reversibility and adaptability, therefore broadening responsiveness to external stimuli and producing accordingly more sophisticated functions. Metal-ligand interactions are strong, directional, and highly versatile driving forces, allowing various coordination geometries and supramolecular polymers with considerable stability yet reversibility. Moreover, metal-ligand coordination may bring unique magnetic, redox, optical, and electrochromic properties, beneficial for potential applications in the fields of heterocatalysis, electronics, gas storage, etc. Therefore, engineering orthogonal host-guest and metal-coordination interactions in supramolecular polymers will definitely endow them with unprecedented complexity and diverse functions. The dimensionality of the materials can grow through iteratively increasing well-defined steps, so we can manipulate each unique noncovalent bond separately to address adaptive properties of the supramolecular polymers. In this thesis, we report the construction of functional supramolecular polymers via orthogonal self-assembly by elegant unification of host-guest complexation and metal-ligand coordination. The main content of the dissertation includes the following five parts:In the first part, we have prepared a reversible, mechanically linked poly[3]rotaxane using an anthracene-based dynamic covalent bond strategy using the benzo-21-crown-7/dialkylammonium salt recognition motif. This dynamic polymerization/depolymerization is controllable by variation of the temperature and photoirradiation. This dynamic covalent bond based on the dimerization of anthracene not only provides a convenient method to fabricate main-chain polyrotaxanes and therefore avoid the dissociation of pseudorotaxanes or polypseudorotaxanes in the polymerization process or the end capping process, but also sheds light on an alternative route for the topological control and diverse smart materials with fine-tuned responsivenesses to external stimuli.In the second part, we have synthesized a novel bis(meta-phenylene)-32-crown-10 derivative bearing two π-extended pyridyl groups and studied its binding to paraquat derivative. The X-ray crystal structure shows that the host-guest complex adopts a threaded geometry with pyridyl nitrogen atoms outside, a sharp contrast to the reported pyridine-functionalized bis(meta-phenylene)-32-crown-10 derivative, which forms a supramolecular cryptand-based taco complex with paraquat. The outside pyridyl nitrogen atoms endow this complex with post-self-assembly behaviour by metal-coordination. Subsequently, we construct a poly[2]pseudorotaxane with a metallosupramolecular polymer backbone via metal-coordination. The combination of various techniques, such as 1H NMR,31P{1H} NMR, DLS, and EDX, comprehensively confirm the formation of this unique metallopoly[2]pseudorotaxane. The dynamic and reversible supramolecular polymer backbone endows the novel polypseudorotaxane structure with adaptive properties.In the third part, a linear supramolecular polymer is constructed by unifying the themes of coordination-driven self-assembly and cryptand-based molecular recognition in a hierarchical orthogonal fashion. Two stepwise self-assembly behaviors as well as a one-pot interaction for the preparation of linear supramolecular polymers are addressed. Cation-induced dynamic properties make the resulting polymer promising candidate for applications in degradable materials. Given the high efficiency of constructing supramolecular coordination complexs and favorable properties induced by host-guest interactions, the unification of these two orthogonal interactions paves an interesting way to construct novel functional materials.In the fourth part, it is demonstrated that the topologies of supramolecular polymers can be efficiently controlled by just changing the orientation of platinum(Ⅱ) acceptor. We design and synthesize a cis-dibenzo-24-crown-8-based cryptand with its pyridine nitrogen atom outside the third arm which can further post-self-assemble into tri-cryptand by metal-coordination with very high efficiency. Upon interacting with a bisparaquat, this tri-arm acceptor is demonstrated to fabricate cross-linked supramolecular polymers at high concentration. More importantly, the cross-linked supramolecular polymer network shows better material properties than that of linear supramolecular polymer, such as the formation of long, macroscopic fibers from cross-linked supramolecular polymer network. In addition, another stepwise strategy and one-pot method also result in the formation of cross-linked supramolecular polymer network based on the consideration of the spontaneous and orthogonal self-assembly behaviors of metal coordination and host-guest interactions. Assembly/disassembly behaviour with cation responsiveness is also observed in this system. Given the rich combinatorial molecular library consisting of complementary building blocks and the high efficiency of constructing supramolecular coordination complexes (SCCs), this work provides a facile and efficient way to control the topologies and exploit intriguing macroscopic properties of the functional supramolecular assemblies.In the last part, we have synthesized a 2-ureido-4-pyrimidinone (UPy)-functionalized [2]rotaxane and investigated the construction of a linear supramolecular rotaxane polymer by hierarchical supramolecular polymerization of a [2]rotaxane driven by quadruple hydrogen bonding motif. A linear polyrhomboid supramolecular copolymer is prepared with high efficiency by means of the directional-bonding approach. Based on the presence of self-complementary UPy units, a homogeneous linear supramolecular copolymer randomly linked by mechanically interlocking moieties and H-bonding metallacycles is obtained by mixing the UPy-functionalized [2]rotaxane and UPy-decorated metallacycle together in one system. This study find that employing organoplatinum(II) metallacycles and rotaxanes as building blocks of supramolecular polymeric backbones enhance supramolecular polymerization efficiency by limiting the formation of cyclic oligomers. Moreover, the orthogonal strategy based on non-covalent bonds used here offers advantages over covalent methods for obtaining advanced structures in a highly modular fashion. As we can control the properties of both precursors in the supramolecular copolymer, the resultant material benefits from the unique functionalities and growing complexity introduced by hierarchical self-assembly. |
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