Photoactive selectively deuterated reactive mesogens targeted for light-controlled opto-mechanical applications

Multifunctional reactive mesogens with lateral methyl substitution in the vicinity of the azo group and selective deuteration on the phenyl ring close to the reactive chain are designed and synthesized. The self-assembly and structural behaviour were established by polarized-light optical microscopy, differential scanning calorimetry and X-ray diffraction techniques. The newly designed materials possess a relatively broad range of the nematic phase. The tilted smectic C phase was detected below the nematic phase for the reactive mesogen without lateral methyl substitution. Due to selective deuteration, the reactive mesogens were studied by 2H-NMR spectroscopy and the orientational order of the deuterated fragment was investigated in the whole mesomorphic range, showing a relatively high main orientational order parameter in both compounds, both in the nematic and SmC phases. The designed photoactive reactive mesogens are intended to be co-monomers for the preparation of multifunctional photoactive liquid crystal elastomers targeted for light-controlled opto-mechanical applications.