Engineering shape memory paper with superior strength, thermal stability, and recyclability through polyimide sizing

Cellulosic paper is an appealing substrate for flexible electronics, yet its modest strength, limited heat tolerance, and intrinsic hydrophilicity constrain performance. We report a polyimide (PI) sizing that permeates the fiber network to create an interpenetrating PI–cellulose framework. The treated paper reaches a tensile strength of 47.1 ± 3 MPa, reported as an ∼700 % gain over the control. It also shows strong chemical tolerance, with <3 % mass loss in acid (pH = 2.6). Reversible hydrogen bonding between PI carbonyls and cellulose hydroxyls mediates bond rupture and re-formation under heat, enabling shape-memory actuation. The glass-transition temperature ( T g ) attains 196 °C-approximately twice that of the control-and the thermal decomposition temperature ( T d ) is 296 °C. Shape memory metrics include 94.6 % recovery and 98.5 % fixation. The system is reprocessable in N , N -dimethylacetamide (DMAc), affording >77 % cellulose recovery and facile reshaping. This practical sizing route recasts paper as a strong, heat-resistant, and recyclable platform for flexible electronics.