Unraveling the charge transfer variation of tetrathiafulvalene-based organic crystals through fragment charge difference calculation

Organic crystals assembled by a well-established family of electron donors, tetrathiafulvalene (TTF)-based molecules, hold great potential for electronics, smart materials, and superconductors. Combining with Marcus' theory and first-principles calculations, we have adopted a fragment charge difference (FCD) method to investigate the charge transfer properties of the TTF-based crystals. Our FCD predictions are highly consistent with those obtained from a well-accepted site energy correction method. We have demonstrated the significant influence of both structure and chemistry on the charge transfer properties using polymorphs, i.e., α-phase tetrathiafulvalene (1) versus β-phase tetrathiafulvalene (2), and crystals with homologous molecular packings, i.e., 1 versus dithiophene-TTF (3). We have also introduced multiple factors to provide further insights into the variation in charge transfer properties of the TTF-based crystals, including energy gap (∆E), centroid distance (ri), orbital distribution correction factor (Hs), and reorganization energy (λ). By taking advantage of our analysis, we have rationalized high mobility in hexamethylene-TTF (4) and low mobility in bis(ethylenedithio)-TTF (5). Our multiple-factor evaluation could support an approach to designing electrically conducting TTF-based materials and provide a method to estimate charge transfer properties effectively

Electroactive liquid crystal elastomers

International audienc

Interpenetrating Liquid Crystal Elastomer and Ionogel as Tunable Electroactive Actuators and Sensors

International audienceElectroactive liquid crystal elastomers (eLCEs) are used to make actuators and soft robotics. However, most eLCEs are monofunctional with one type of deformation (bending or contraction). Recently, a trilayer eLCE are reported by combining ion-conducting LCE and ionic electroactive polymer device (i-EAD). This i-EAD-LCE is bifunctional and performs either bending or contractile deformation by controlling low-voltage stimulation. Nevertheless, it has a Young's modulus of only 1.63 MPa. To improve the mechanical performance, the i-EAD-IPN-LCE is prepared here, whose central membrane is composed of interpenetrating LCE and ionogel (i-IPN-LCE) instead of a single ion-conducting LCE. This i-EAD-IPN-LCE with a typical thickness of 0.5 mm can function not only as linear and bending actuators, but also as a sensor. As a linear actuator, its Young's modulus, actuation stress, and strain are 51.6 MPa, 0.14 MPa and 9%, respectively, reaching skeletal muscles’ values. As a bending actuator, its bending strain difference Δε is 1.18% with 3 mN output force. It can also operate as a sensor producing 0.4 mV Open-Circuit-Voltage to respond to bending deformation (Δε = 9%). Therefore, this i-EAD-IPN-LCE is a promising system for the fabrication of robust electroactive devices and sensors with multiple degrees of freedom