Abstract
<jats:p>In modern stereolithography, photopolymer chemistries are rapidly diversifying while geometric constraints remain minimal, pushing the technique from prototyping to manufacturing. Consequently, mechanical performance is critical. Tough bulk networks are difficult because high crosslink density and network heterogeneity yield stiff, brittle parts, whereas very soft materials print poorly due to low crosslinking. Although high crosslink density enables fast, high-resolution printing, it narrows thermomechanical tunability. We address this trade-off with a cleavable, siloxane-containing crosslinker that lowers crosslink density on demand after printing. Parts are printed efficiently with a highly crosslinked network, then photodegraded to tailor properties from stiff and tough to PDMS-like softness. Cleavage is triggered by light: a UV-only photoacid generator, latent under the longer wavelengths used for 3D printing, catalytically cleaves siloxane bonds, removing siloxane-derived crosslinks. We evaluated formulations containing 10–50 double-bond percent (db%) siloxane crosslinker in an ethyl-hexyl methacrylate matrix via tensile testing and dynamic mechanical analysis before and after cleavage. Swelling and leaching experiments quantified the extent of siloxane degradation. Finally, we demonstrated high-precision printing with the optimal formulation at 50 db% crosslinker, validating a pathway to decouple printability from post-print thermomechanical performance.</jats:p>