Cleavable and Depolymerisable Networks in Vat Photopolymerisation: Triggered Disassembly, Fragment Identity and Closed-Loop Qualification
Segurola, Juan
2026-08-27 · Informe · Versión 1.1
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Vat photopolymerisation normally produces insoluble crosslinked networks whose geometry is fixed by carbon-carbon or other persistent covalent bonds. Recent material strategies introduce acid-labile crosslinkers, thioester weak links, reversible thioester-anhydride bonds, exchangeable thiourethanes, cyclic disulfides, photolabile crosslinkers and degradable ring-opening-metathesis linkages so that printed objects can later be disassembled. The resulting literature uses overlapping terms such as degradable, recyclable, reprintable, depolymerisable and closed-loop, although these terms describe different evidence levels. This review distinguishes a soluble linear polymer from a cleavable network, a degradable network from a depolymerisable one, and recovered matter from qualified feedstock. Direct VPP examples show that geometry and transport strongly control apparent disassembly: acid-cleavable PEG lattices dissolve differently from cubes; a 2 wt% thionolactone additive permits basic-solvent degradation while centimetre- scale dense objects require much longer than thin features; and thioester networks can be designed for controlled degradation and filler recovery. More circular routes recover thiol-terminated oligomers from printed poly(thio)urethanes or regenerate lipoate resin components for repeated printing. However, these processes differ in fresh reactive input, catalyst, solvent, temperature, purity, yield and whether recovered chemistry is compositionally equivalent to the original resin. Dissolvable supports and linear reprintable polymers are valuable adjacent routes but do not establish network depolymerisation. The proposed qualification architecture therefore requires direct evidence of connectivity loss, identification and quantification of recovered species, complete process-stream mass balance, fresh-input accounting, reprinting under a declared formulation and cycle-resolved property retention. No universal acceptance threshold is proposed. The central principle is: dissolution is an observation; network cleavage is a mechanism; recovery is a mass balance; and closed-loop recycling is a cycle-level evidence claim.