In situ formation of photoalignable N-benzylideneaniline side groups and control of photoinduced reorientation in polymethacrylate with 4-oxybenzaldehyde side groups and 4-methoxyanilline composite films

We investigate control of the photoinduced orientation of photoalignable polymeric films from polymethacrylate with 4-oxybenzaldehyde side groups (1) and monomeric 4-methoxyanilline (2) composites, where both 1 and 2 have no photoreactivity. Annealing the 1/2 composite film with various 1/2 ratio generates N-benzylideneaniline (NBA) side groups, which exhibit photoreactivity and photoinduced molecular reorientation when irradiated with linearly polarized (LP) 365 nm light. Adjusting the 1/2 mixture ratio controls the amount of NBA side group's formation, as well as the photoinduced orientation performance of the film. Analyses of the three-dimensional refractive indices reveal biaxial photoinduced reorientation for a 1/2 film saturated with NBA side groups (∼96%), while in-plane motion plays a major role for 1/2 films containing unreacted 4-oxybenzaldehyde side groups. Furthermore, a post-annealing procedure after exposure greatly amplifies the in-plane reorientation structure for film consisting of more than 75% NBA side groups, which exhibits LC characteristics. [Display omitted] •Photoalignable N-benzylideneaniline (NBA) side groups is formed from non-photoreactive polymer/monomer composites.•The formed NBA side groups show photoinduced orientation behavior when the film is exposed to linearly polarized UV light.•The generated photoalignment performance is controlled by adjusting the composite ratio.•Annealing the reacted film enhances the generated birefringence.