Mechanoluminescent Polymer Nanocomposites:Design,Synthesis And Applications

With the development of polymer mechanochemistry,mechanochemiluminescent polymer materials can act as stress sensors for dectecting covalent bond scission sensitively,which is crucial for the research of the mechanical response behavior and fracture mechanism of polymer materials.We herein utilized the chemiluminescent mechanophore(bis(adamantyl)-1,2-dioxetane)as the stress sensor,and synthesized mechanochemilumninescent polymethyl acrylate/cellulose nanocrystals(PMA/CNCs)nanocomposites and waterborne polyurethane/carbon dots(WPU/CDots)nanocomposites.These mechanochemiluminecent polymer composites exhibited good mechanical properities.With mechanochemiluminescent method,covalent bond scission was visualized sensitively,and the failure mechanism was studied at molecular level.The results can be summarized as follow:1.A series of nanocomposites based on cellulose nanocrystals(CNCs)and polymethyl acrylate(PMA)with covalently incorporated 1,2-dioxetane as a luminescent mechanophore were prepared.Through surface-initiated single-electron transfer radical polymerization,the CNCs nanofiller offers good compatibility with polymer matrix.As a consequence,all the composite materials exhibit reinforced mechanical properties with increased stiffness and strength.Most importantly,1,2-dioxetane is demonstrated as a sensitive platform to characterize the dissipation pathway of fracture energy,as well as the polymer chain scission in the Mullins effect within these polymer nanocomposites.The combined use of mechanical macroscopic testing and molecular bond scission data herein provides detailed information on how force distributes and failure occurs in complex soft materials.2.Hydrophilic carbon dots with excellent fluorescence performance were synthesized and served as energy transfer acceptors of broken 1,2-dioxetane.Based on physical blending and covalent incorporation methods,carbon dots were introduced into waterborne polyurethanes containing 1,2-dioxetane mechanophores.These waterborne polyurethane/carbon dots(WPU/CDots)nanocomposites exhibited bright mechanochemiluminescence and good mechanical performance.It improves the luminescent intensity of broken 1,2-dioxetanes in waterborne polymers,and offers new opportunities and methods for further study of mechanochemiluminescence behavior and failure meachainsm in waterborne polymer materials.