Utilizing Polyhexahydrotriazine (PHT) to Cross-Link Polyimide Oligomers for High-Temperature Shape Memory Polymer

Integrating good strength and toughness, high thermostability, and easy processability into one shape memory polymers is highly desirable yet challenging. Herein, we demonstrate an approach to fabricate high temperature shape memory polymer based on polyhexahydrotriazines (PHT) cross-linked polyimide oligomers. The obtained thermosets with enhanced thermal and mechanical properties can comparable to well-established high molecular weight polyimide. The thermoset with molecular weight of polyimide oligomer as low as 8 kg/mol (PI8k-PHT) exhibit the tensile strength, fracture toughness, and elastic modulus of 90 MPa, 69 MJ/m3, and 2059 MPa, respectively. The PI8k-PHT show good shape memory effect at 210 °C with shape fixity above 98% and shape recovery above 90%, and their temporary shapes quickly recover to original within 4 s under thermal stimulus. Besides, utilizing the partially cured prepregs sheets and further compression molding methods, the block or surface micropatterned shape memory composites can be facilely obtained.