Polymeric Polyaldehyde Approach to Develop Robust Dynamic Covalent Adaptive Polyimine Networks

Polyimine-based covalent adaptive networks crosslinked with Schiff bases (PI-CANs) have been developed as effective building blocks to construct advanced polymeric materials possessing reprocessability, self-healability, and sustainability. Most approaches to fabricate PI-CANs involve the synthesis and use of small molecule polyaldehydes. Herein, we report a versatile approach exploring the synthesis of polymeric polyaldehydes (PP-CHO) with a polyacrylate backbone bearing pendant aldehyde groups to develop self-healable, reprocessable polyacrylate-PI hybrid CANs. The approach centers on the synthesis of well-defined poly(2-hydroxyethyl acrylate) bearing aldehyde pendants (PHEA-CHO) by a photo-indued reversible deactivation radical polymerization,(Photo-RDRP) followed by post-polymerization modification. The PHEA-CHO is highly reactive to an aliphatic diamine, enabling the fabrication of transparent, integrated, dynamic PHEA-PI hybrid CAN films. They exhibit lower activation energy (E_a = 14.6 kcal/mol) for stress relaxation even at mild temperature (50°C - 80°C) and good self-healability and reprocessability as retaining their mechanical strengths upon a recycle. Promisingly, they degrade to corresponding aldehyde and amine precursors through acid-catalyzed hydrolysis of benzoic imine crosslinks, offering potential for sustainability as recyclable dynamic covalent systems. These results suggest that the PP-CHO approach is versatile for the development of dynamic PI-CAN materials capable of the built-in ability for extended operation and enhanced reliability.