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Traditionally, slide-ring gels are stretchable but soft as a result of an elasticity-stretchability trade-off. Herein, we introduce a new approach to breaking this trade-off and creating reinforced slide-ring networks with mobile crosslinkers. Our approach involves the construction of a polyethylene glycol double-threaded γ-cyclodextrin-based pro-slide-ring crosslinker that serves as a modular component for 3D printing and copolymerization. The resulting crystalline-domain-reinforced slide-ring hydrogels, or CrysDoS-gels, exhibit both high elasticity and high stretchability. The modular synthesis allows for high-throughput synthesis of CrysDoS-gels, generating a large amount of data for structure-property analysis. By employing data science techniques, such as machine learning and linear regression, not only were we able to identify which chemical components influence the mechanical properties of CrysDoS-gels, but this analysis also aided in the discovery of better-performing CrysDoS-gels. Finally, we demonstrate the potential application of the newly discovered CrysDoS-gels as sensing devices by 3D printing them as stress sensors with high sensitivity and a broad detection range. 

The exciting advancements in 3D-printing of soft materials are changing the landscape of materials development and fabrication. Among various 3D-printers that are designed for soft materials fabrication, the direct ink writing (DIW) system is particularly attractive for chemists and materials scientists due to the mild fabrication conditions, compatibility with a wide range of organic and inorganic materials, and the ease of multi-materials 3D-printing. Inks for DIW need to possess suitable viscoelastic properties to allow for smooth extrusion and be self-supportive after printing, but molecularly facilitating 3D printability to functional materials remains nontrivial. While supramolecular binding motifs have been increasingly used for 3D-printing, these inks are largely optimized empirically for DIW. Hence, this review aims to establish a clear connection between the molecular understanding of the supramolecularly bound motifs and their viscoelastic properties at bulk. Herein, extrudable (but not self-supportive) and 3D-printable (self-supportive) polymeric materials that utilize noncovalent interactions, including hydrogen bonding, host–guest inclusion, metal–ligand coordination, micro-crystallization, and van der Waals interaction, have been discussed in detail. In particular, the rheological distinctions between extrudable and 3D-printable inks have been discussed from a supramolecular design perspective. Examples shown in this review also highlight the exciting macroscale functions amplified from the molecular design. Challenges associated with the hierarchical control and characterization of supramolecularly designed DIW inks are also outlined. The perspective of utilizing supramolecular binding motifs in soft materials DIW printing has been discussed. This review serves to connect researchers across disciplines to develop innovative solutions that connect top-down 3D-printing and bottom-up supramolecular design to accelerate the development of 3D-print soft materials for a sustainable future. 

Thermo-responsive 3D-printed hydrogels that are composed of methylated α-cyclodextrin polyrotaxanes have been synthesized through post-3D-printing methylation. With a high methylation degree of the threaded α-cyclodextrins, the fabricated monolith exhibits a two-stage thermo-induced aggregation behavior, in which a second micro-crystallization process was identified for the first time. The methylated polyrotaxane monoliths possess reversible temperature-dependent size, transparency, and elastic moduli switching in an aqueous environment. Through dual-material 3D printing, the 3D-printed monolith actuates back-and-forth at different temperatures. 

Abstract The development of integrated systems that mimic the multi‐stage stiffness change of marine animals such as the sea cucumber requires the design of molecularly tailored structures. Herein, we used an integrated biomimicry design to fabricate a sea cucumber mimic using sidechain polypseudorotaxanes with tunable nano‐to‐macroscale properties. A series of polyethylene glycol (PEG)‐based sidechain copolymers were synthesized to form sidechain polypseudorotaxanes with α‐cyclodextrins (α‐CDs). By tailoring the copolymers’ molecular weights and their PEG grafting densities, we rationally tuned the sizes of the formed polypseudorotaxanes crystalline domain and the physical crosslinking density of the hydrogels, which facilitated 3D printing and the mechanical adaptability to these hydrogels. After 3D printing and photo‐crosslinking, the obtained hydrogels exhibited large tensile strain and broad elastic‐to‐plastic variations upon α‐CD (de)threading. These discoveries enabled a successful fabrication of a sea cucumber mimic, demonstrating multi‐stage stiffness changes. 

Abstract The development of large pore single‐crystalline covalently linked organic frameworks is critical in revealing the detailed structure‐property relationship with substrates. One emergent approach is to photo‐crosslink hydrogen‐bonded molecular crystals. Introducing complementary hydrogen‐bonded carboxylic acid building blocks is promising to construct large pore networks, but these molecules often form interpenetrated networks or non‐porous solids. Herein, we introduced heteromeric carboxylic acid dimers to construct a non‐interpenetrated molecular crystal. Crosslinking this crystal precursor with dithiols afforded a large pore single‐crystalline hydrogen‐bonded crosslinked organic framework H_COF‐101. X‐ray diffraction analysis revealed H_COF‐101 as an interlayer connected hexagonal network, which possesses flexible linkages and large porous channels to host a hydrazone photoswitch. Multicycle Z/E‐isomerization of the hydrazone took place reversibly within H_COF‐101, showcasing the potential use of H_COF‐101 for optical information storage.