Thi H. Le

Covalent adaptable networks (CANs) offer a compelling strategy to unite the mechanical robustness of thermosets with the reprocessability of thermoplastics, yet achieving simultaneous durability, processability, and true recyclability remains challenging. We introduce diketoenamine (DKE) vitrimers derived from β ‐triketone methacrylate monomers and demonstrate how rational monomer design dictates network processability, viscoelasticity, and recyclability. By systematically varying the spacer length between the β ‐triketone (TK) moiety and the polymer backbone, we identify a key structure–property relationship that dictates vitrimer behavior. Networks bearing TK pendants minimally displaced from the backbone suppress creep but exhibit limited stress relaxation, whereas extended spacers yield lower glass transition temperatures, higher effective crosslink densities, and efficient stress dissipation, enabling optical transparency and reprocessability. Extending this platform to ultra‐high molecular‐weight prepolymers introduces physical entanglements as secondary crosslinks, further enhancing dimensional stability without compromising processability. Both mechanical and chemical recycling validate the closed‐loop circularity of these materials. These results establish TK methacrylates as a versatile platform for designing high‐performance vitrimers that integrate durability, reprocessability, and true closed‐loop recyclability.

Vitrimers, a class of covalent adaptable networks (CANs), promise sustainability through recyclability and reprocessability, yet suffer from creep under prolonged stress due to dynamic bond exchange. Here, a materials design strategy is reported that integrates polymerization‐induced self‐assembly (PISA) to embed core‐crosslinked nanoparticles within vitrimer networks, yielding hierarchical dual‐crosslinked systems with a reduction of creep susceptibility by up to 90% at 150 °C yet good reprocessability at elevated temperatures ( E _a = 246 kJ mol ⁻¹ ). These spherical nanostructures restrict chain mobility and act as rheological modifiers that can be synthetically tuned through core block length. This approach offers precise architectural control, leveraging nanoparticle phase morphology to direct bulk vitrimer properties. This study establishes a new paradigm for creep‐resistant CANs and showcases how PISA can advance vitrimer performance by structurally encoding mechanical robustness and reprocessability.

We report a method to produce ultrahigh-molecular-weight (UHMW, >10⁶ Da) styrenic polymers with tunable entanglement molecular weights (M_e). The high number of primary chain entanglements (≫10) results in good mechanical strength and dimensional stability at elevated temperatures while maintaining melt and solution reprocessability over multiple cycles with no change in the viscoelastic behavior or molecular weight distributions. We use mild photoiniferter polymerization to synthesize copolymers of alkoxy-functionalized styrenics and pentafluorostyrene (PFS). The electronic mismatch of the electron-rich styrenics with electron-deficient PFS provided enhanced cross-propagation rates, which enabled access to UHMWs under reasonable reaction times. We tune M_e by pre- and postpolymerization modification of the styrenic repeat units with n-alkyl pendants of variable lengths. This enables modulation of M_e over a range of 40,000-160,000 Da, which provides tunable Young's moduli over a range of 0.04-69 MPa. Moreover, the UHMW polymers possess good creep recovery (>50%) up to 125 °C, despite glass transition temperatures (T_g) ranging from -14 to 52 °C. Specifically, this side-chain tunability enables various unique thermomechanical behaviors, including room-temperature shape memory. Furthermore, the high solution viscosity of the UHMW polymers allows the processing of these materials into fibers, which is not possible in lower-molecular-weight counterparts of identical chemical composition and concentration. This study establishes a novel route to UHMW polymers comprised solely of styrenic backbones, with readily tunable viscoelastic and thermomechanical properties through the systematic engineering of M_e.

Photoactivation of nitroarenes has been recently reported to induce the transformation of alkenyl bonds into carbonyl functionalities. Capitalizing on this unique photochemical mechanism, this study explores the use of nitroarenes to achieve oxidative cleavage of olefinic polymers under visible light irradiation. The degradation of various olefinic polymers, including commercially available polybutadiene, polynorbornene, both linear and cyclic poly(phenylacetylene), as well as backbone-modified polyacrylates with alkenyl functionality was investigated. To elucidate the efficacy of this methodology, a series of nitroarene derivatives bearing variable substituents were screened for their degradative efficiency on polybutadiene. Varying nitroarene stoichiometry, reaction temperature, and pos-treaction workup conditions were investigated to optimize degradation conditions. The results demonstrated that photoexcited nitroarenes enable efficient oxidative degradation of olefinic polymers in a safe and sustainable manner, providing a novel strategy for mild macromolecular deconstruction.