Studies Of Crown Ether And Pillararene- Based Supramolecular Polymers

Supramolecular polymers,the combination of supramolecular chemistry with polymer science,are defined as polymeric systems that extend beyond the molecule and utilize noncovalent interactions to control the self-assembly of monomeric units into larger polymeric architectures.Supramolecular polymers can be constructed by non-covalent interaction of low molecular weight molecules or high molecular weight polymers.To date,Macrocylic hosts,including crown ethers,cyclodextrins,calixarenes,cucurbiturils,and pillararenes,have been widely utilized to fabricate host-guest interaction-based supramolecular polymers.Among them,the host-guest interaction between crown ethers,as the first generation of host moleculaes,and guest molecules has been widely used to assemble interlocked molecules and supramolecular polymers.Morever,pillararenes,was firstly reported in 2008,have beenemployed to fabricate various supramolecular assemblies.Thus,in this dissertation,wereported the construction of supramolecular polymers and the fabrication of functional supramolecular polymeric materials via the non-covalent interaction of crown ether and pillararene-based recognition motifs.The major contents of this dissertation are as follows:（1）In the first part,a novel A₂-B₃-type supramolecular hyperbranched polymer was prepared based on the benzo-21-crown-7/secondary ammonium salt recognition motif.A homotritopic monomer containing three Benzo-21-crown-7 units and a complementary homoditopic monomer containing two secondary ammonium salt units were firstly synthesized.They can self-assemble to form a SHP in a concentrated solution.The host-guest interaction of A₂ with B₃ was studied by the combination of various techniques,such as ¹H NMR,COSY NMR,2D NOESY NMR,viscosity measurements,DLS,and TEM.The experimental results demonstrated that the formation of SHP is dependent on the initial concentration of two monomers.The resulting SHP exhibited stimuli-responsive behavior,their disassembly–assembly could be switched by addition or removal of K⁺.With the stimuli-responsive feature,it may inspire interest for further fabrication of topological supramolecular materials with desired functionalities.（2）In the second part,two heteroditopic monomers H1 and M1 were synthesized.The two monomers can self-sorting assemble to form supramolecular alternating polymer at high concentration based on B21C7-secondary ammonium salt binding interaction and pillar[5]arene-based host–guest complexation.The supramolecular alternating polymer presents ion and competitive guest-responsive characteristic.Furthermore,the resulting supramolecular alternating polymers can be employed to prepare hierarchical materials from0D spherical aggregates to 1D nanofibers,to 2D microstructure films,and finally to 3D ordered glue by carefully evaporating the solvent of polymer solution,electrostatic spinning,breath figure method and heating-cooling the polymers at high concentration,respectively.This study will be helpful in designing and preparing supramolecular hierarchical materials with different dimensions.（3）In the third part,a novel“D₃-AC-E₃”triple-monomer methodology was proposed to construct supramolecular hyperbranched alternating polymers.Two rigid homotritopic monomers tris（per-methylated pillar[5]arene）（D₃）and tris（benzo-21-crown-7）（E₃）,and a heteroditopic monomer bearing a dialkylammonium salt and a neutral guest moiety,were prepared.The supramolecular hyperbranched alternating polymer was formed by selective binding interaction between the pillar[5]arene moiety with the neutral guest moiety and between the benzo-21-crown-7 group and the dialkylammonium salt group.The triple-monomer system was found to effectively avoid the formation of cyclic oligomers/gels/precipitates usually formed in the traditional“A₂+B₃”double-monomer system.This study will be helpful in designing supramolecular hyperbranched polymers with controllable structure and function.（4）In the fourth part,a transformation from a supramolecular hyperbranched homopolymer to a supramolecular hyperbranched alternating copolymer was successfully conducted by a competitive self-sorting method.Two heterotritopic monomers AB₂ and CD₂were designed and synthesized.The AB₂ could self-organize to form a supramolecular hyperbranched homopolymer via an inclusion interaction between the pillar[5]arene and secondary ammonium salt moieties.Upon the addition of equimolar CD₂ to the CDCl₃ solution of AB₂,the AB₂-based supramolecular hyperbranched homopolymer was disrupted and then reassembled into a new supramolecular hyperbranched alternating copolymer with CD₂ based on the competitive self-sorting binding between B21C7-secondary ammonium salt and pillar[5]arene-TAPN.The experimental results also demonstrated that the formation of both the supramolecular hyperbranched homopolymer and the alternating copolymer depend on the initial concentration of monomers.This study provides inspiration for designing different structural and functional supramolecular copolymers.