Enhanced Thermal Ageing Stability of Mechanophore in Polyurethane Network by Introducing Polyhedral Oligomeric Silsesquioxanes (POSS)

Spiropyran (SP) shows excellent ability in light- or force-triggered color and fluorescence generation. However, it has the fatal weakness of poor antithermal bleaching properties in polymers, especially when exposed to severe environments, which will shorten the life of mechanical responsive materials. Here, a strategy is reported to protect SP through incorporation of multifunctional polyhedral oligomeric silsesquioxanes (POSS) as cross-linkers into a polyurethane network. The introduction of POSS not only improves the mechanical strength of the elastomer, but also enhances the thermal stability of the mechanophore, showing much more sensitive force-responsive and photoresponsive properties, especially after thermal annealing. POSS contributes to the construction of a 3D network and hinders the mobility of the hard domains of molecular chains, thus enhancing the thermal stability of the mechanophore in the network. The strategy can not only extend the life of the stimuli-responsive materials, but also promote the application temperature of the mechanically responsive polymers.