Morphological and Computational Analysis of Additively Manufacturable Polyimide Precursors: Implications for Rationally Designing New Polyimide Structures

In this work, photocurable polyimide precursors are additively manufactured via vat photopolymerization and thermally post‐processed into bulk polyimide discs. Two polyimide structural variants were additively manufactured, post‐processed, and characterized: the conventional pyromellitic dianhydride/4,4′‐oxydianiline (PMDA/ODA), and one based on PMDA/4,4’‐diaminodiphenyl sulfone (PMDA/DDS). The morphologies of both variants were studied as a function of post‐processing temperature. Scanning electron microscopy experiments reveal that the bulk morphologies of all printed parts are homogeneous below 350°C. Post‐processing at and above 350°C results in prevalent internal voids, which are more severe in the PMDA/DDS parts. Small/wide‐angle X‐ray scattering experiments reveal that the crystalline domains in PMDA/DDS parts are more loosely organized than the PMDA/ODA parts. Atomistic simulations reveal that the sulfone linkage of PMDA/DDS disrupts pi‐stacking of aromatic rings of neighboring chains, resulting in a profound reduction in interaction strength between adjacent polymer units in PMDA/DDS compared to PMDA/ODA. Ultimately, the reduced thermal stability of PMDA/DDS parts is attributed to disordering of the PMDA/DDS crystallites. This work presents the first in‐depth study of the structure‐morphology relationships of additively manufacturable polyimide precursors throughout post‐processing. These insights will inform future work focused on the development of new polyimides with stable semicrystalline morphologies.