Photomobile Polymer Materials with Crosslinked Liquid‐Crystalline Structures: Molecular Design, Fabrication, and Functions

Abstract

Crosslinked liquid-crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction-expansion and bending-unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.

Coupling Mechanical and Electrical Properties in Spin Crossover Polymer Composites

“…[1][2][3][4][5][6][7][8] Beyond purely mechanical applications, these compounds represent a particularly attractive scope for the development of chemomechanical, biomimetic, and other complex systems combining built-in actuator, sensor, and energy harvesting functions, which is the key requirement for achieving highly integrated, versatile, and adaptive actuator systems. [9][10][11][12] Among these smart molecules, the important reversible volume change of molecular spin-crossover (SCO) switches Indeed, out of this window the mechanical and electrical properties of P(VDF-TrFE) change due to the proximity of the Curie temperature in the high temperature range and relaxation phenomena at low temperatures.…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…50,67,184,217,218 When partial cross-linked structure is introduced into polymers that exhibit LC phases (Figure 1, right, bottom), elastomeric properties emerge at ambient temperature. [217][218][219][220][221] Seminal studies of Finkelmann focused on the development of partially crosslinked side-chain LC polymers. 222,223 These polymers are self-standing materials that exhibit elastic properties and memory effects.…”

“…When the nematic or smectic LC elastomers are macroscopically aligned, selective shrinkage strain along the director vector is observed during the LC-isotropic phase transitions. 45,47,[219][220][221][222][223][224][225][226][227] Light-induced deformations have been widely explored in crosslinked azobenzene-based LC networks. 220,228 The stimuli response of these materials rely on the light driven cis-trans/trans-cis photoisomerizations of azobenzene groups that act as photochromic molecules Functional liquid-crystalline polymers T Kato et al and as mesogens.…”

“…220,228 For example, Broer group reported on photo-responsive artificial microstructured cilia that bend upon the appropriate light stimuli. 231 These cilia are composed of two parts that have distinct response to light.…”

Supramolecular design principles for efficient photoresponsive polymer–azobenzene complexes

“…Here, we review the progress made since 2009, focusing on the material design concepts for fabricating efficient photoresponsive materials through ionic, hydrogen and halogen bonding between the host polymers and small molecules. In 2014, Faul summarized the use of ionic self-assembly for supramolecular materials, briefly including photoresponsive azobenzene complexes, 53 Ube and Ikeda reviewed recent developments in photomobile azobenzene-based materials, 54 and Seki reviewed mainly covalent photoresponsive liquid crystal polymers, 44 complemented by a review and a highlight article by Yu. 55,56 In 2013, Priimagi et al wrote an account on using halogen bonding in the design of functional materials 57 and, in 2015, they reviewed halogen bonding in the context of photoresponsive azobenzene-containing materials.…”