Construction And Properties Study Of Novel Mechanically Interlocked Polymers Based On Rotaxanes

Rotaxane dendrimers are a novel type of high-order mechanically interlocked molecules(MIMs),in which one or more rotaxane units are introduced into the dendrimer.Owing to the integrated combination of the dynamic properties of rotaxanes and the highly branched three-dimensional architecture of dendrimers,rotaxane dendrimers have been used to construct novel artificial molecular machines and supramolecular dynamic materials.Various rotaxane dendrimers have been constructed and shown a wide range of applications in artificial light-harvesting systems,photocatalysis,and supramolecular smart materials.It should be pointed out that it’s of great significance to understand the relationship between the microscopic motion of rotaxane dendrimers and the macroscopic properties of smart materials,which will be helpful to guide the design and synthesis of new smart materials.However,it’s generally used to construct intelligent-responsive materials by blending rotaxane dendrimers with traditional polymers,it’s difficult to accurately understand the relationship between the microscopic motion of rotaxane dendrimers and macroscopic properties(structure-property relationships).By combining the dynamic properties of supramolecular polymers with the stability of covalent polymers,the mechanically interlocked polymers based on rotaxanes display unique macroscopic properties,such as excellent mechanical performances,stimulus-responsiveness and self-healing properties,by accumulating and amplifying the microscopic motion of rotaxane structures at the molecular level,such as the rotation and sliding of the wheel components of rotaxanes,it is helpful to deeply understand the structure-property relationships,the thesis focuses on the construction of novel functionalized rotaxane dendrimers and the further explorations of their properties and applications.On the one hand,a novel functional rotaxane dendrimers were construction and explored their applications in artificial light-harvesting and light emitting devices.On the other hand,rotaxane dendrimers were introduced into linear polymers and polymer networks to prepare mechanically interlocked polymers,and explored the relationship between their microscopic motion and macroscopic properties.The thesis can be divided into four parts:In Chapter One,firstly,the development of rotaxanes is introduced,especially the synthetic methods and their applications in artificial molecular machines.Secondly,the research progress of dendrimers is described.In addition,the synthetic strategies and applications of rotaxane dendrimers is summarized.Finally,a detailed introduction on mechanically interlocked polymers based on rotaxanes is presented.In Chapter Two,starting from a TPE-functionalized [2]rotaxane precursor as key branching building block and DSA-functionalized [2]rotaxane as core,a new family of wheel-branched rotaxane dendrimers was construction through a controllable divergent approach.The resultant wheel-branched rotaxane dendrimers contain up to twenty-eight TPE moieties(energy donor)on the axle and one DSA moiety(energy acceptor)on the axle at the central core.Notably,artificial light-harvesting systems with better energy transfer efficiencies and antenna effects have been successfully constructed based on these wheel-branched rotaxane dendrimers,in which both donor and acceptor are AIEgens.Finally,the wheel-branched rotaxane dendrimers have been used to prepare white emission LED as solid-state fluorescent materials.In Chapter Three,a novel type of dendronized polymer was first proposed and synthesized via the ring-opening metathesis polymerization(ROMP)of macromonomers.More importantly,the existence of multiple switchable [2]rotaxane units within the dendron skeleton endows the resultant rotaxane-branched DPs with attractive stimuli-responsive features.Upon the addition or removal of external stimulus that trigger the motions of the rotaxane branching points away from or close to the polymer backbone,the stretching or contracting of the rotaxane-branched dendrons will result in an increased or decreased thickness,thus further leading to tunable thermal and rheological properties by the microscopic motion of rotaxane units.In Chapter Four,starting from a norbornene-functionalized [2]rotaxane precursor,a new family of rotaxane-branched dendrimers has been construction through a controllable divergent approach,which is the first example of rotaxane-branched dendrimers as crosslinker.The resultant rotaxane-branched dendrimers contain up to twenty-one norbornene moieties(crosslinking sites).Furthermore,the resultant rotaxane-branched dendrimers were further employed as crosslinkers for the construction of novel super-soft elastomers by cross-linked with polydimethylsiloxane(PDMS)macromonomers.Rheological tests were further used to study the dynamic behaviour of the polymer networks.Compared with the traditional bottlebrush polymer networks,the elastomer networks exhibits unique main chain entanglement and excellent thermal expansion performance.