Construction And Stimuli-Responsive Properties Of Pillar[5]arene-Based Supramolecular Polymer Materials

As an important section of supramolecular chemistry,the birth of each generation of macrocyclic compounds will bring great contribution to the progress of supramolecular materials.Their exquisite design,efficient synthesis,diverse post-modification,and excellent host-guest assembly have always been the research hotspots in the related areas.Pillar[n]arenes（n=5-15）,as the fifth generation of supramolecular macrocyclic host molecules after crown ethers,cyclodextrins,calixarenes,and cucurbiturils,have been widely used in multiple fields such as the preparation of supramolecular polymeric materials,chemical/biological sensing and detection,adsorption and separations,and molecular machines,due to their unique structural characteristics,superior host-guest binding abilities,and various functionalization modes.Supramolecular polymer materials are regarded as advanced functional materials featured with complicated architectures and unique functions,where the individual building blocks（units）are interconnected by reversible noncovalent interactions such as hydrogen bonding,metal coordination,hydrophilic/hydrophobic interactions,π-πstacking,van der Waals forces,electrostatic forces,and host-guest recognition,etc.Under specific external stimuli,it can undergo continuous and spontaneous assembly/disassembly processes.Thus,supramolecular polymer materials typically have characteristics that differ from those of traditional covalent polymer materials,including reversibility,tunability,stimuli responsiveness,adaptability,degradability,reusability,and other intriguing properties.Up to now,supramolecular polymer materials based on pillararenes have been widely reported and have shown promising application potentials in the field of sensing and detection,nanotherapy,catalysis and cell imaging.However,there remain certain shortcomings and deficiencies in this domain,such as simple and momotonous response,relatively poor stability and mechanical properties,and the limited selectivity and universality.Orthogonal/hierarchical self-assembly is a feasible and practical assembly mode,which can perfectly combine two or more noncovalent interactions into complexed supramolecular assemblies.The macroscopic properties of the material could be tuned by exerting one type of external stimulus at a time,which can not only boost the preparation of supramolecular materials with facile syntheses,novel structures,and unique functions,but also significantly enhance the stability and enrich the stimuli responsiveness of the obtained materials.Therefore,the orthogonal/hierarchical self-assembly strategy provides a highly efficient and powerful approach to fabricate the stimuli-responsive supramolecular poymer materials based on pillararenes.In this thesis,we designed and synthesized a series of functionalized pillar[5]arene host molecules and corresponding linear guest molecules as building blocks to prepare stimuli-responsive supramolecular poymer materials based on pillar[5]arene via host-guest assembly by rationally introducing multiple noncovalent interactions.The main content of this thesis mainly includes the following three parts:In the first part,we have designed and synthesized a benzo[f]coumarin derivative-functionalized pillar[5]arene BXDSP5 and a symmetric B-B type neutral guest G-（CN）₂possessing two cyano sites and triazole sites at its ends.A stimuli-responsive supramolecular polymer network（G-（CN）₂?BXDSP5）with aggregation-induced emission（AIE）properties has been efficiently constructed by host–guest interactions between BXDSP5 and G-（CN）₂,which shows excellent fluorescence properties due to the AIE effect and desirable ion-sensing abilities in both solution and solid states,holding great potential in the fluorescence detection for Fe³⁺.The resultant G-（CN）₂?BXDSP5 can be transformed into supramolecular polymer gel at high concentration via multiple noncovalent interactions,exhibiting various stimuli-responsive behaviors,including thermal-responsiveness,mechanical-responsiveness,and competitive agent-responsiveness.Meanwhile,the xerogel of supramolecular polymer material has been successfully used to remove Fe³⁺from water with high adsorption efficiency.In addition,an ion-responsive film based on supramolecular polymer has also been developed,which can serve as a practical and convenient fluorescence test kit for detecting Fe³⁺.In the second part,we designed and synthesized a bis-thioacetylhydrazine functionalized copillar[5]arene host（SHP5）and a disulfide bond-bridged bis（viologen functional groups）-modified B-B type guest（DSPy）.A novel metallosupramolecular polymer network（DSPy?SHP5@Zn）has been constructed by the hierarchical self-assembly of SHP5,DSPy,and Zn²⁺ions,in which host-guest recognition and metal-ligand coordination interactions play a crucial role.Owing to the reversible feature of both dynamic covalent and noncovalent interactions,the DSPy?SHP5@Zn assembly can form metallosupramolecular gels,which show good gel-sol transition properties in response to various external stimuli,including temperature,redox,p H changes,and competitive guests.The DSPy?SHP5@Zn assembly can serve as an excellent dual-channel sensor for highly selective recognition of OH^ˉ.Therefore,a convenient and feasible test kit for sensing OH^ˉbased on DSPy?SHP5@Zn is fabricated.The present work provides a facile and efficient method to construct multi-stimuli-responsive smart gels,which may further enrich and expand the scope and application of smart supramolecular materials.In the third part,we designed and synthesized a pyrene-functionalized pillar[5]arene host（Py P5）and a bis（dialkylammonium salt）-based B-B type guest（S₂NH₂）.By rationally introducing host-guest recognition andπ-πstacking interactions between Py P5 and S₂NH₂,a supramolecular polymer（Py P5?S₂NH₂）with supramolecular assembly-induced emission enhancement properties was prepared.Meanwhile,the formation of the supramolecular polymer highly depends on the host and guest concentration.With the increasing concentration of Py P5 and S₂NH₂,the structures of Py P5?S₂NH₂ can be transformed from linear to cross-linked networks.Moreover,Py P5?S₂NH₂ can be sensitive to multiple stimuli,including temperature,redox,UV-light,p H,solvent polarity,organometallic compound,and competitive guest.This study provides a facile approach for synthesizing fluorescent supramolecular polymers with multiple stimuli-responsive properties,holding promising application prospect in the fields of fluorescent sensing,drug release,smart materials and so on.