Photo-crosslinkable liquid-crystalline azo-polymer for surface relief gratings and persistent fixation

Highly efficient migration has been observed for soft liquid-crystalline azobenzene-containing polymer films to form surface relief gratings (SRGs). The efficient migration is probably driven by the interfacial instability at boundaries between the smectic liquid-crystalline phase and photoinduced isotropic one. However, this migration system suffers from long-term and heat stability. This work proposes a new post-fixation method by utilizing the [2 + 2] photo-dimerization reaction of a cinnamoyl unit introduced into the polymer. The polymer synthesis, the properties of SRG formation, and drastic improvement of the stability towards heating and solvent exposure are described.