# Breaking the paradox: simultaneous recovery of phosphorescence and mechanical properties in polymeric films

## TL;DR

A new method enables polymeric films to recover both phosphorescence and mechanical properties simultaneously through covalent cross-linking.

## Contribution

A covalent cross-linking strategy is introduced to achieve simultaneous recovery of phosphorescence and mechanical performance in polymeric films.

## Key findings

- Films with covalent cross-linking showed over 90% recovery of phosphorescence and mechanical properties after healing.
- Theoretical simulations confirmed the low energy required for covalent bond re-formation during healing.
- Multi-emission phosphorescence was achieved by reassembling film fragments with different chromophores.

## Abstract

Polymeric films with self-healable room temperature phosphorescence (RTP) and mechanical performance are eagerly anticipated for wearable and electronic devices. However, simultaneously recovering phosphorescence and mechanical properties remains a great challenge due to improper interactions quenching phosphorescence and the inherent conflict between chain rigidity and flexibility in polymeric films. Herein, we propose the use of a chromophore binder between the polymer matrix to fabricate RTP films with simultaneous recovery of phosphorescence and mechanics. A covalent cross-linking network was established, restricting the molecular motion of chromophore binders to achieve bright deep-blue phosphorescence emissions. Additionally, the films exhibited processability, flexibility, stretchability, and self-healing ability. Both the phosphorescent and mechanical properties could be recovered with an efficiency of more than 90% for the films healed in water under room temperature. Theoretical simulation showed that this noteworthy self-healing capacity could be ascribed to the relatively low energy for the formation and re-formation of the covalent cross-linkage between the chromophore binders and polymer matrix. Accordingly, we realized an assembly–reassembly process for multi-emission phosphorescence by healing film fragments using different chromophores with boronic acid groups. It is anticipated that this facile and universal strategy via covalent cross-linkage could provide possibilities for the design of multi-functional optical materials with expanded application fields.

We have realized the simultaneous recovery of phosphorescence and mechanical properties for polymeric films based on covalent cross-linking between the chromophore binders and polymer matrix.