The electro-optical behavior of polymer stabilized cholesteric texture cells has been investigated for three different polymers. The switching process was studied with respect to the electric field dependence of the diffuse reflectivity, diffuse transmittance, and the dynamics of the reorientation process. For certain polymer concentrations, a two-stage reorientation process was observed. This behavior is consistent with the cholesteric liquid crystal being divided between two distinct environments. In the first, the liquid crystal is strongly dominated by the polymer network, while in the second a bulklike behavior, comparable to the unstabilized cholesteric material, is observed. Scanning electron micrographs of the polymer networks further support this model. Measurements of the diffuse scattering indicate that the polymer influenced regions contribute largely to the observed back scattering, whereas the bulklike material contributes primarily to forward scattering.

A detailed investigation of the influence of operating temperature on the electrochemical reduction of CO2 to formate at tin oxide loaded gas diffusion electrodes (GDEs). Ambient pressure electrolysis is performed between 20 and 70 °C with a focus on maximizing current density and energy efficiency while maintaining an average formate faradaic efficiency of at least 80 %. The best performance is achieved at a temperature of 50 °C, which allows a current density of 1000 mA cm−2. Lower or higher temperatures both show an increased hydrogen evolution at said current density. Further investigation of CO2 transport limitation revealed a minimum at 50 °C, which is explained by the opposing influence of temperature on CO2 diffusion coefficients and solubility. This explanation is supported by an estimate of the current density at which hydrogen evolution starts to increase based on the flooded agglomerate model. Long‐term operation for 24 h also revealed an optimum temperature of 50 °C, which helps to suppress the increasing rate of hydrogen evolution and with that a mechanical degradation of the GDE.

Reversible optical control of transmittance in polymer/liquid crystal composite films by photoinduced phase transition

No abstract

No abstract