Supramolecular Functional Materials Based On Mechanically Interlocked [2] Catenane

Mechanically interlocked molecules have attracted increasing attention,especially after the achievements in designing artificial molecular machines.The interlocked macrocycles of the catenane can rotate and move easily within each other,endowing the molecular components with high degrees of freedom and mobility compared with conventional covalently connected molecules.Scientists also proved that the incorporation of catenane units into polymer backbones influences the rheological,mechanical,and dynamic properties of the resulting materials.However,no general method yet exists to effectively incorporate catenanes into materials and exploit their interlocked architectures and dynamics.In this thesis,we made some novel combination between supramolecular chemistry,mechanically interlocked molecules,and polymer science in order to make functional supramolecular polymer materials.The main content of the dissertation includes four parts as following:In the first part,we constructed a supramolecular main-chain polycatenane by orthogonal metal ion coordination and pillar[5]arene-based host-guest interaction.This convenient method,involving host-guest interaction and coordination-driven self-assembly,has been shown to efficiently incorporate catenanes into supramolecular polymers.The glue-sol transition of the supramolecular polycatenane could be realized by either increasing the temperature or adding OH-ions.The rheology measurements between the catenane-based supramolecular polymer and a traditional supramolecular polymer were conducted to investigate the unique feature of a mechanically interlocked structure and the results showed that the supramolecular main-chain polycatenane gave better viscoelastic behavior.In the second part,we synthesized a novel supramolecular mechanically interlocked crosslinker and used it to further construct supramolecular polymer network.By comparing with a traditional supramolecular crosslinker,the mechanically interlocked polymer network showed much better viscoelastic properties which were confirmed by viscosity and rheological measurements.Moreover,at high monomer concentration,the resulting supramolecular polymer network gel exhibited thermo-,pH-,and chemo-responsive sol-gel transition behaviors.This study paved the way for combining the ease of processing and stimuli-responsiveness of host-guest interactions and the unique mechanical features of MIMs to construct novel supramolecular polymer networks.In the third part,we synthesized a bisvinyl[2]catenane,in which the rotation and movement of two macrocycles are restricted by intercomponent hydrogen bonding(IHB).Proton NMR measurements revealed that the destruction and reformation of IHB can be mediated by external stimuli such as pH and temperature changes,leading to switching between flexible and rigid states of the catenane.Then[2]catenane was utilized as the crosslinker to construct a polymer gel which exhibited mechanically adaptive properties,as confirmed by rheological and mechanical tests.The adaption of the gel relies on the reversible tuning of macrocycle’s mobility,rather than the variation of the chain rigidity or crosslinking density.Therefore,this adaptive mechanism is novel,providing a new way to mimic the observed response of sea cucumber dermis.More importantly,we have demonstrated that incorporating small"molecular machines" into bulky polymers is an effective strategy to create adaptive materials.In the last part,we synthesized a linear polycatenane with two thiol groups in both ends,and further utilized "click" reaction to prepare polycatenane-based gel.First,we used single molecular force spectroscopy to analyze the dynamic property of polycatenane at molecule level.Then through FT-IR and DSC measurements we confirmed the structure of polycatenane-based gel.After getting the mechanical properties of the bulky polymer gel,we found that in our system the dynamic behavior at molecule level could be nicely connected with the corresponding macroscopic properties.More interestingly,our polycatenane-based gel showed excellent solvent content controllability and solvent resistance,which was rarely reported before.