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Although the famous brittle characteristics of molecular crystals are unfavorable when they are used as flexible smart materials (FSMs), an increasing number of organic crystal-based FSMs have been reported recently. This breaks the perception of their stiff and brittle properties and promises a bright future for basic research and practical applications. Crystalline smart materials present considerable advantages over polymer materials under certain circumstances, rendering them potential candidates for certain applications, such as rapidly responsive actuators, ON/OFF switching, and microrobots. In this review, we summarize the recent developments in the field of organic crystal-based FSMs, including the derivatives of azobenzene, diarylethene, anthracene, and olefin. These organic crystal-based FSMs can bend, curl, twist, deform, or respond otherwise to external stimuli, such as heat or light. The detailed mechanisms of their smart behaviors are discussed with their potential applications in exciting intelligent fields. We believe this review could provide guidelines toward future fabrication and developments for novel organic crystal-based FSMs and their advanced smart applications. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version Huang Y, Gong Q, and Yu J acknowledge the AME Programmatic Funding Scheme of Cyber Physiochemical Interfaces (CPI) project (#A18A1b0045) and Singapore National Research Foundation Fellowship (NRF-NRFF11-2019-0004). Huang Y is thankful for the start-up funds of the Youth Talent Support Program from Xi’an Jiaotong University.

This communication reports a unique ultra-large sheet formation through hierarchical self-assembly of a rod–coil graft copolymer containing a rigid polyphenylene backbone and flexible poly(ethylene oxide) (PEO) side chains. The hierarchical self-assembly process involved a distinctive morphological transition of 1D helical to 2D superstructures. The graft copolymer offers a new chance for the challenging bottom-up fabrication of ultra-large self-assembled nanosheets in solution, as well as a novel system for fundamental studies on 2D self-assembly of polymers.

This article presents a facile and effective approach for synthesizing three-dimensional (3D) graphenecoupled Schiff-base hierarchically porous polymers (GS-HPPs). The method involves the polymerization of melamine and 1,4-phthalaldehyde, yielding Schiff-base porous polymers on the interconnected macroporous frameworks of 3D graphene aerogels. The as-synthesized GS-HPPs possess hierarchically porous structures containing macro-/meso-/micropores, along with large specific surface areas up to 776 m² g⁻¹ and high nitrogen contents up to 36.8 wt%. Consequently, 3D nitrogen-enriched hierarchically porous carbon (N-HPC) materials with macro-/meso-/micropores were obtained by the pyrolysis of the GS-HPPs at a high temperature of 800 °C under a nitrogen atmosphere. With a hierarchically porous structure, good thermal stability and a high nitrogen-doping content up to 7.2 wt%, the N-HPC samples show a high specific capacitance of 335 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH, a good capacitance retention with increasing current density, and an outstanding cycling stability. The superior electrochemical performance means that the N-HPC materials have great potential as electrode materials for supercapacitors.