Carbon Dots Intensified Mechanochemiluminescence from Waterborne Polyurethanes as Tunable Force Sensing Materials

1,2-Dioxetane is a well-known chemiluminescent mechanophore allowing real-time monitoring of polymer chain scission,but usually suffers from fluorescence quenching in polar environments.Herein,a series of mechanochemiluminescent waterborne polyurethanes/carbon dots composites(WPU-CDs)have been synthesized by incorporating fluorescent CDs to promote the energy transfer process in different environments.The resulting bulk WPUs,and in particular,their swollen films filled with a large amount of polar solvents(water and ionic liquid)emit intense mechanochemiluminescence.Thus force-induced covalent bond scission and stress distribution within these different WPU-CDs films can be sensitively visualized.Furthermore,the ionic liquid containing films exhibited both electrical and luminescent signal changes under stretching,which offer a new kind of force sensor responsive at a broad detecting strain range and for multi-mode strain analysis.This study is expected to stimulate new research endeavors in mechanistic insight on waterborne polyurethanes and the corresponding stretchable sensing devices.

Covalently Cross-Linked and Mechanochemiluminescent Polyolefins Capable of Self-Healing and Self-Reporting

Compared with non-cross-linked and dynamically covalent polymers,covalently cross-linked networks are irreplaceableinmany areas;however,they aredifficult to repair once fractured,due to limited polymer chain diffusion after cross-linking.Herein,the authors have reported a newkind of permanently cross-linked polyolefin,which when attached with amide side groups,yieldmechanically robust yet readily repairablematerials.A key is to use low cross-linking density,which enables satisfactory elasticity and chain mobility for thermodynamically favored healing.Another key is to incorporate dense hydrogen bonds that can undergo reversible associations.These factors jointly promise polyolefin networks with good mechanical properties and self-healing performance(recovered spontaneously up to 96%of its original tensile strength).More importantly,by means of mechanochemiluminescence from 1,2-dioxetane,which serves as the cross-linker and built-in self-reporting stress probe,a microscopic evaluation of how the chain entanglement proceeds upon healing and how failure occurs in the network can be obtained.

Wide-ranging Force Responsive Composites based on 1,2-Dioxetane and ZnS as Luminescent Probes in Polyurethanes

Combining the advantages of mechanochemiluminescence from 1,2-dioxetane and elastico-mechanoluminescence from ZnS particles,a new kind of mechanoluminescent polymer composites are developed.They can emit bright luminescence with two distinct colors at different strains,empowering a verstaile mechanochemical strategy for force sensing and damage detection at a wider force responsive range.