Effect of carbon black on the photomobile properties of liquid crystal polymers with or without azobenzene moieties.

In this work we studied the possibility to induce or modify the photomobile properties of liquid crystal polymers by introducing different concentrations (from 0 up to 1 wt.%) of carbon black (CB) in several polymers containing or not azobenzene mesogens. These units can undergo a reversible photoisomerization from $trans$ to $cis$ configuration in the presence of UV light by inducing bending in the corresponding films. The morphological and optical properties, as well as the photomobile behaviour of pristine and composite films were investigated and compared. Concerning the photomobile properties, photoresponsivity measurements were studied in the wavelength range 457--747 nm to investigate how the presence of the CB affects the photomobile response inside and outside the absorption spectral region of LC-polymers. Choosing appropriately the CB concentration, we demonstrated that it is possible to induce photomobile behavior in non-active polymers or enlarge the usable spectral bandwidth of the azo-benzene--based samples in visible region towards the visible and near infrared spectral region. The work was supported by the UE FET PULSE-COM and Eureka investor funded POC ALICE projects.