Mechanical Motion and Modulation of Thermal‐Actuation Properties in a Robust Organic Molecular Crystal Actuator

Abstract

Dynamic molecular crystals are thought to be an emerging functional material with enormous tunability in physicochemical properties. Here, a smart crystal, 6‐Chloronicotinic acid (6‐CNA), is reported, responding to heat stimulus by bending, splitting‐to‐self‐healing, and jumping, induced thermally by a reversible single‐crystal‐to‐single‐crystal phase transition. This phase transition proceeds by a well‐organized migration of the habit plane, which is reproducible after more than twenty phase transition cycles. The temperature function introduced externally can realize a reversible migration of the habit plane and also act as a jump switch. A comprehensive analysis of the microscopic observations demonstrates that the heterogeneity of phase transition and the homogeneity of self‐driven orientations account for the splitting‐to‐self‐healing. Utilization of the reversible phase transition of 6‐CNA single crystal can generate a pushing force that is > 104 times the gravitational force of the crystal, thus making 6‐CNA an actuator to drive the reversible movement of a glass plate. Both forms of these crystal materials are mechanically compliant in two dimensions and can be twisted in terms of requirement. This excellent actuation performance, reversibility of the phase transition, and soft nature make it a prospective candidate for robust single‐crystal actuators.

Stimuli-responsive flexible organic crystals

“…21, 4h ), which responds to heat stimuli by bending, splitting-to-self-healing, and jumping when induced thermally by a reversible single-crystal-to-single-crystal phase transition. 137 Moreover, both forms of these crystalline materials are plastic in two dimensions and can be twisted as required. It was believed that the crystal integrity is retained because the structural matching between the converted phase and the parent phase reduces the elastic strain energy and prevents the destruction of the crystal to some extent.…”

Creation of asymmetrically constructed cylindrical liquid crystal actuators with controllable thermal rolling

“…Thermally driven LC actuators have become increasingly popular in recent years. [2][3][4][5] In addition, LC actuators stimulated by electric power, [6][7][8][9][10] UV light, 11,12 near infrared (NIR) [13][14][15][16][17][18] and fluid [19][20][21] were also designed.…”

Structural origins of two-dimensional elastic bending in a nonaromatic organic molecular crystal

“…10,11 Mechanical flexible crystals are usually classed as plastic crystals and elastic crystals according to the deformation manner that responds to the mechanical force stimulus. For plastic crystals, a general structure characteristic of the known examples is that the molecule assembles via pÁ Á Áp stacking interactions to bound molecular columns and the adjacent columns usually interact by weak interactions, typically light halogen bonding 12 and weak hydrogen interactions, 13,14 to form the slip plane. As for the elastic crystals, three typical hypotheses 15 have been proposed, including the interlocked crystal packing and isotropic interaction hypothesis, 16,17 fibril lamella morphology hypothesis 18,19 and the molecular movement hypothesis.…”