Effect of local electric field on trans to cis photo-isomerization of azobenzene containing polymer

Highlights: • Electric field effect on the rate of isomerization of azobenzene molecule is studied. • Local electric field is realized by adding polar PVDF in the ultrathin film. • The change in the energy barrier of the photoisomerization due to PVDF is calculated. We report the effect of local electric field on the rate of photo-isomerization of azobenzene containing poly ethylene glycol-itaconate based side chain liquid crystalline polymer (PEGIA) in the ultra-thin film at air–water interface. The local electric fields were realised by adding polar polyvinylidene difluoride (PVDF) molecules in the PEGIA thin film. The ultra-thin film of PEGIA mixed with PVDF in different weight percentages were formed at air–water interface and are characterized using surface manometry technique. The rate constant of $\mathrm{trans}-\mathrm{cis}$ photo-isomerization ($k_1$) of azobenzene moieties in the presence of different amounts of PVDF were obtained from the surface pressure measurements. We find that the $k_1$ exponentially increases with the percentage composition of PVDF which can be attributed to the effect of electric field due to the dipole moment of the PVDF molecules. The change in the activation energy of the photo-isomerization as a function of percentage composition of PVDF is calculated.