Photo-isomerization effects on orientations of azobenzene-labeled polymer films measured by second harmonic generation

Abstract

We have studied the changes in the orientational distribution functions of azobenzen-labeled polyamic acid monolayers before and after photoisomerization by measuring optical second-harmonic generation (SHG). From the surface SHG data, we determined the nonlinear-optical tensor components of the monolayers before and after the photo-isomerization. It is found that the point symmetry of the azo-pendant units in the monolayer changes from C ∞υ to C 1υ by the photo-isomerization.