Photo‐Degradable Polyester Networks and Multi‐Photon Printed Objects Based on Cyclic Ketene Acetals

ABSTRACT Radical ring‐opening polymerization (RROP) of cyclic ketene acetals (CKAs) constitutes a powerful avenue to biodegradable polyesters via radical polymerization. CKA‐based degradable polymers have been established mainly as linear polymers, while networks from CKA‐based RROP remain scarce despite their potential as degradable materials. Herein, a photoreversible RROP‐polyester network based on poly(2‐methylene‐1,3,6‐trioxocane) (PMTC) is introduced. Photoreversibility is achieved by decorating the PMTC chains with pendant pyrene chalcone (PyChal) moieties. Photoinduced [2+2] cycloaddition ( λ max = 440 nm) of the PyChal moieties affords covalent cross‐links, while irradiation at λ max = 345 nm allows for network reversion as underpinned by an in‐depth solution assessment of the photochemistry. The reversible nature of the photochemistry enables repeatable gel‐sol transitions as shown by variations in their storage and loss modulus (resulting in G ’ changes of up to 9 kPa). Importantly, the photoreactive CKA‐based polymer can be employed in light‐driven multi‐photon printing (MPP) without the need for any initiators, allowing the fabrication of pre‐determined spatially confined architectures as evidenced by ToF‐SIMS. The MPP structures can be degraded by expore to UV irradiation and alkaline conditions. We thus establish a degradable PCKA‐based resist with reversible photochemistry for modular soft matter manufacturing.