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

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. ... mehrThe 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.