We report the synthesis of ultra‐high molecular weight (UHMW) poly( N,N ‐dimethylacrylamide) (PDMAm) hydrogels with extremely low crosslinking densities by trithiocarbonate photoiniferter‐mediated reversible deactivation radical polymerization (RDRP). Fixing the photoiniferter to crosslinker ratio and gradually increasing the targeted degree of polymerization ( DP _target ) allowed for simultaneous control over the crosslinking density and the average molecular weight ( M _n ) of the primary chains, both below and above the critical molecular weight of entanglement ( M _c ). Interestingly, a plateau in storage moduli ( G’ ) was observed for UHMW PDMAm hydrogels with a sufficiently high DP _target (>5,000), indicating a transition to the entanglement‐dominated regime, with no contribution from crosslinks to the overall modulus, thus indicating the formation of highly entangled hydrogels. These hydrogels exhibit enhanced properties such as high toughness and resistance to swelling despite their vanishingly small crosslinking densities. Furthermore, even when equipped with cleavable crosslinkers, the UHMW PDMAm hydrogels resist degradation due to dense entanglements which act as transient crosslinks preventing the gels from swelling, while sparse covalent crosslinks help to maintain their structural integrity and avoid chain disentanglement. This approach allows simple synthesis of elastic and tough hydrogels with a well‐defined structure and tuneable contributions from both crosslinks and entanglements.

α-Lipoic acid, and its ester ethyl lipoate, were copolymerised with n-butyl acrylate and a crosslinker to install labile disulfide bonds within the strands of the resulting polymer networks enabling their degradation, reformation and self-healing.

The chemical recycling of commodity acrylic polymers, such as the transparent thermoplastic polymethyl methacrylate (PMMA), typically requires temperatures of 350-400°C. Herein, we report chemical recycling back to monomers for PMMA between 120-180°C, through UV illumination under oxygen-free conditions. We have achieved gram-scale degradation of consumer plastic with >95% conversion, yielding >70% monomer, which can be readily repolymerized. The process proceeds even at high concentrations (>1 M) and depends strongly on solvent choice: aromatic solvents like dichlorobenzene and diphenyl ether maximize conversion. In contrast to a concurrently published study, we report that chlorine radicals are not required for depolymerization; however, when present, they react with the unzipping chain to form chlorine-functionalized PMMA which can be upcycled through derivatization. In more sustainable non-chlorinated solvents such as benzonitrile, minimal termination by radicals enables complete unzipping. These findings demonstrate a low-temperature, scalable route for the chemical recycling of PMMA, offering alternative pathways for plastic circularity.

We report the synthesis of ultra‐high molecular weight (UHMW) poly( N,N ‐dimethylacrylamide) (PDMAm) hydrogels with extremely low crosslinking densities by trithiocarbonate photoiniferter‐mediated reversible deactivation radical polymerization (RDRP). Fixing the photoiniferter to crosslinker ratio and gradually increasing the targeted degree of polymerization ( DP _target ) allowed for simultaneous control over the crosslinking density and the average molecular weight ( M _n ) of the primary chains, both below and above the critical molecular weight of entanglement ( M _c ). Interestingly, a plateau in storage moduli ( G’ ) was observed for UHMW PDMAm hydrogels with a sufficiently high DP _target (>5,000), indicating a transition to the entanglement‐dominated regime, with no contribution from crosslinks to the overall modulus, thus indicating the formation of highly entangled hydrogels. These hydrogels exhibit enhanced properties such as high toughness and resistance to swelling despite their vanishingly small crosslinking densities. Furthermore, even when equipped with cleavable crosslinkers, the UHMW PDMAm hydrogels resist degradation due to dense entanglements which act as transient crosslinks preventing the gels from swelling, while sparse covalent crosslinks help to maintain their structural integrity and avoid chain disentanglement. This approach allows simple synthesis of elastic and tough hydrogels with a well‐defined structure and tuneable contributions from both crosslinks and entanglements.