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Structurally ordered soft materials that respond to complementary stimuli are susceptible to control over their spatial and temporal morphostructural configurations by intersectional or combined effects such as gating, feedback, shape‐memory, or programming. In the absence of general and robust design and prediction strategies for their mechanical properties, at present, combined chemical and crystal engineering approaches could provide useful guidelines to identify effectors that determine both the magnitude and time of their response. Here, we capitalize on the purported ability of soft intermolecular interactions to instigate mechanical compliance by using halogenation to elicit both mechanical and photochemical activity of organic crystals. Starting from (E)‐1,4‐diphenylbut‐2‐ene‐1,4‐dione, whose crystals are brittle and photoinert, we use double and quadruple halogenation to introduce halogen‐bonded planes that become interfaces for molecular gliding, rendering the material mechanically and photochemically plastic. Fluorination diversifies the mechanical effects further, and crystals of the tetrafluoro derivative are not only elastic but also motile, displaying the rare photosalient effect. [ABSTRACT FROM AUTHOR]

The photomechanical effects of crystals of halogen‐substituted 9‐anthracenecarbonitrile were investigated. The needle‐like crystals of 10‐fluoroanthracene‐9‐carbonitrile (FCNA) bend rapidly under irradiation with 365 nm, 410 nm light and even white light, and the bent crystal could almost recover to its original shape upon exposure to 254 nm light or heating. The reversible photo‐induced mechanical behaviors originated from [4+4] cycloaddition and the reverse reaction. This type of photoactuator, in response to light irradiation over a broad wavelength range from UV to the visible region, might have important applications in biomimetic systems, biomedicine, artificial muscles, and smart microrobotics. The rapid photo‐induced mechanical movements of the crystals inspired us to fabricate a hybrid polymer film of polyvinylidene difluoride incorporated with the microcrystals of FCNA, which not only showed bending toward or away from the light source depending on the initial bending direction of the film, but also could lift small objects induced by remote light. [ABSTRACT FROM AUTHOR]

The polymorphs of 2ClChMe‐4 in Form I (ribbon‐like crystal) and Form II (block‐like crystal) were prepared, and they exhibited curling/flipping and expansion upon heating on account of single‐crystal‐to‐single‐crystal transformations. The irreversible phase transformations occurred separately at 53.2 °C and 57.8 °C for the crystals in Form I and Form II, during which the molecular conformation of 2ClChMe‐4 changed and the molecules slipped along the (100) plane. Movement at the molecular level resulted in changes of cell parameters, which in turn led to macroscopic motions of the crystals upon heating. Additionally, the ribbon‐like crystals of 2ClChMe‐4 showed photo‐induced bending driven by [2+2] cycloaddition. Accordingly, an actuator showing reversible bending behavior was fabricated triggered by light and heat successively. Like biomimetic self‐actuators, such multi‐stimuli mechanical responsive molecular crystals might have potential applications in soft robots, artificial muscles and microfluidic systems. [ABSTRACT FROM AUTHOR]