A sustainable closed-loop manufacturing would become reality if commodity plastics can be upcycled into higher-performance materials with facile processability. Such circularity will be realized when the upcycled plastics can be (re)processed into custom-designed structures through energy/resource-efficient additive manufacturing methods, especially by approachable and scalable fused filament fabrication (FFF). Here, we introduce a circular model epitomized by upcycling a prominent thermoplastic, acrylonitrile butadiene styrene (ABS) into a recyclable, robust adaptive dynamic covalent network (ABS-vitrimer) (re)printable via FFF. The full FFF processing of ABS-vitrimer overcomes the major challenge of (re)printing cross-linked materials and produces stronger, tougher, solvent-resistant three-dimensional objects directly reprintable and separable from unsorted plastic waste. This study thus offers an imminently adoptable approach for advanced manufacturing toward the circular plastics economy.

This study reports on the use of sodium alginate to effectively stabilize sodium sulfate decahydrate (Na2SO4·10H2O, SSD) based phase change material (PCM) for application as a thermal energy storage material. Alginate/SSD composite PCMs were prepared by blending SSD with different concentrations of alginate polymer. The resulting composite PCMs demonstrate high phase change enthalpy ∼160 J/g and extended cycling stability compared to existing PCM composites. The analysis carried out by optical microscopy, X-ray scattering, and periodic density functional theory (DFT) calculations demonstrated that the stabilization effect was caused by the interplay between ionic and hydrogen bond interactions between the alginate and SSD. Additionally, the variation in mechanical properties of PCM composites with polymer concentrations made it possible to formulate a composite that maintains stable performance after 3D printing. The advanced properties make this composite a promising candidate for application as a thermal energy storage material.

Dynamic metal-coordinate cross-links impart smart and superior physicochemical properties in their deployments in many biological and artificial metallopolymer networks in various stages of solidification via dehydration. Nonetheless, a quantitative model that describes to what extent the dynamic behaviors of metal-coordinate bond transition from the hydrated to the dehydrated state is missing. In previous work, we have shown that local water binding helps metal-coordinate bonds to maintain their dynamic properties during bulk network dehydration, thereby offering mechanical damping properties to the network deep into the dehydrated solid state. Using mussel-inspired hydrogels with chemically tuned fractions of metal-coordinate cross-links, here, we reveal the direct scaling relationship between the macroscopic relaxation time of the dehydrated network and the amount of microscopic water bound by metal-coordinate cross-links. This quantitative relationship between dehydrated metal-coordinate network mechanics and metal-coordinate cross-link dynamics may help us better understand and emulate the sustainable process of solidification via spatiotemporally controlled dehydration of load-bearing materials on wide display in nature.