Construction And Property Investigation Of Supramolecular Polymers Cross-linked By Discrete Metallacycles

Supramolecular polymers are polymer systems formed based on non-covalent interactions and self-assembly.At present,the research of supramolecular polymers has been developed from the initial construction by a single non-covalent bond to the use of multiple non-covalent bonds,and even non-covalent bonds can be introduced into the polymer chains to prepare specific functional polymers.Although a lot of progress has been made in the field of supramolecular polymers,the demand for novel construction strategies and functional supramolecular polymers with multiple functions is still urgent.We presented the construction and properties research of different types of supramolecular polymers crosslinked by metallacycles through hierarchical selfassembly in this dissertation based on the research basis of our group in coordinationdriven self-assembly.There are seven parts in this dissertation:Chapter one,we reviewed the recent research progress of hierarchical selfassembly based on metal-coordination interaction and the research progress of supramolecular polymers.At the end of this chapter,we put forward our projects in this dissertation.Chapter two,we designed and successfully synthesized two 120° pyridine donor with different sizes,the longer one was decorated with a pillar[5]arene unit and the shorter one was decorated with a neutral cyano guest unit.These two different sized ligands can be used to generate two different sizes metallacycles after stirring with the 120° platinum acceptor by self-sorting through “one-pot” method.Then supramolecular polymers can be constructed by the host-guest interaction between the pillar[5]arene unit and the neutral cyano guest unit.The supramolecular polymers transformed into gels under higher concentration,reversible gel-sol transitions were successfully realized stimulated by various external stimuli such as temperature,competitive guest,and halide,etc.Chapter three,a 120° pyridine donor containing two cyano units and a tetraphenylethylene(TPE)unit was synthesized,and then a rhomboidal metallacycle containing four cyano units was obtained by coordination-driven self-assembly.Besides,a molecule containing two pillar[5]arene units was synthesized as a linker.Supramolecular polymers were then generated through host-guest interactions.It should be noted that the obtained supramolecular polymer displayed interesting AIE properties due to the restriction of TPE intramolecular motions within the polymeric network.More importantly,by taking advantages of dynamic nature of both coordination bonds and host-guest interactions,the resultant supramolecular polymer displayed dual stimuli-responsive fluorescent transitions under different stimuli such as the competitive guest and halide anion.Chapter four,we constructed two supramolecular polymer gels with multiple stimuli-responsive properties through hierarchical self-assembly.Firstly,by decorating the tetraphenylethylene(TPE)core with two dipyridyl moietis and two pillar[5]arene units,a new 120° dipyridyl donor was successfully prepared.Then,a rhomboidal metallacycle with four pillar[5]arene units and a hexagonal metallacycle with six pillar[5]arene units were constructed through coordination-driven self-assembly,respectively.Subsequently,the corss-linked supramolecular polymers were formed through host-guest interactions upon the addition of ditopic guest.The obtained supramolecular polymers were able to transform into supramolecular polymer gels under higher concentration,which displayed AIE properties due to the restriction of TPE intramolecular motions within three-dimensional polymeric network.By taking advantages of dynamic nature of both coordination bonds and host-guest intereactions,the resultant supramolecular polymer gels displayed multiple stimuli-responsive gelsol transitions under different stimuli,such as temperature,competitive guest,and halide,etc.,along with the “on-off” of the fluorescence emission.Chapter five,a rhomboidal metallacycle containing two types of crown ethers was constructed by coordination-driven self-assembly.Two-dimensional supramolecular polymers were successfully constructed by adding two bidentate guests.Based on the dynamic reversibility of the host-guest interaction,the reversible transformation of the supramolecular polymer topology can be achieved through the introduction and removal of competitive guests.We have studied and characterized this series of processes through nuclear magnetic resonance spectroscopy.Chapter six,firstly,a pillar[5]arene derivative containing one methacrylate unit and a pillar[5]arene derivative containing two methacrylate units were successfully obtained by rational design,and their crystal structures were obtained.The pillar[5]arene unit was successfully introduced into linear polymer chain and crosslinked polymer by radical polymerization with different monomers.Metallacycle containing cyano guest unit and tetraphenylethylene unit can be successfully introduced into the polymeric network by host-guest interactions,while exhibits aggregationinduced emission properties.Chapter seven,the crown ether unit and the chain transfer agent unit were introduced into the rhomboidal metallacycle by the coordination-driven self-assembly strategy.Then,polymer chain was successfully introduced into the metallacycle by the post-assembly polymerization strategy.Based on the gelation properties of the introduced polymer chains,a hydrogel containing a metallacycle skeleton was successfully prepared.Rheology studies had found that the mechanical strength of the hydrogel can be enhanced by the host-guest interaction between the crown ether unit and the bidentate guest.