Manipulation of the ferroelectricity in LC polymers via photomechanical isomerization of azobenzene moieties

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Abstract
We report the synthesis and characterization of a new ferroelectric liquid crystalline side chain copolymer containing photoisomerizable chromophores and non‐photoisomerizable mesogenic units. On illumination with UV‐light a suppression of the polar order is obtained as indicated by a substantial drop of the spontaneous polarization (PS) compared to the dark state. We interpret this as the phase order being disrupted by the cis‐isomer of the chromophore. After illumination with VIS‐light only the major part of Ps is restored. The photochemical cis‐trans back‐isomerization (restoration of the phase) leads to a different stationary state than the dark state of the material. The thermal reisomerization (cis‐trans) in the liquid‐crystalline phase was observed to be faster than in solution by one order of magnitude.