Three‐dimensional (3D) printing and especially VAT photopolymerization leads to cross‐linked materials with high thermal, chemical, and mechanical stability. Nevertheless, these properties are incompatible with requirements of degradability and re/upcyclability. We show here that thionolactone and in particular dibenzo[c,e]‐oxepane‐5‐thione (DOT) can be used as an additive (2 wt %) to acrylate‐based resins to introduce weak bonds into the network via a radical ring‐opening polymerization process. The low amount of additive makes it possible to modify the printability of the resin only slightly, keep its resolution intact, and maintain the mechanical properties of the 3D object. The resin with additive was used in UV microfabrication and two‐photon stereolithography setups and commercial 3D printers. The fabricated objects were shown to degrade in basic solvent as well in a homemade compost. The rate of degradation is nonetheless dependent on the size of the object. This feature was used to prepare 3D objects with support structures that could be easily solubilized.

The present investigation describes an original structure−reactivity relationship within a series of type II photoinitiators designed on the basis of a multibranched molecular engineering strategy. Each photoinitiator indeed incorporates a triphenylamine subunit decorated with a combination of parasubstituents, implying anisole or thioanisole as π-conjugated donor groups and multiple reactive ketones as electron-acceptor functions. Interestingly, we demonstrate that the photoinitiating efficiency of such multipolar derivatives is mainly modulated by a solvent-mediated interplay between intersystem crossing and intramolecular charge transfer processes at the excited singlet state. Such a balancing mechanism drastically regulates the population of highly reactive excited triplet species in such a manner that the photoinitiation performance of the dyes can be enhanced by more than 1 order of magnitude within the series. Taking advantage of this amplified photoreactivity, we illustrated the versatile application potential of the best-performing photoinitiating prototype, which was both employed both in a rapid two-dimensional (2D) photopatterning process through liquid crystal display (LCD) image projection and in three-dimensional (3D) micro-optics fabrication at the surface of an optical fiber.

3D printing and especially VAT photopolymerization leads to cross-linked materials with high thermal, chemical and mechanical properties. Nevertheless, such stability is incompatible with degradability and re/upcyclability. We showed here that thionolactone and especially dibenzo[c,e]-oxepane-5-thione (DOT) could be used as an additive (2 wt%) to acrylate-based resins to introduce weak bonds into the network via a radical ring-opening polymerization process. The low amount of additive allows to only slightly modify the printability of the resin, keep intact its resolution and maintain the mechanical properties of the 3D object. The resin with additive was used in UV microfabrication and 2-photon stereolithography setup and commercial 3D printers. The fabricated objects were shown to degrade in basic solvent as well in a home-made compost. The rate of degradation is nonetheless dependent of the size of the object. This feature was used to prepare 3D objects with support structures that could be easily solubilized.