Aggregation: A new mechanism of relaxation of polar order in electro-optic polymers

A new relaxation mechanism of poled thin films nonlinear optical properties, arising from the accelerated chromophore aggregation under heating, was shown. Second order nonlinear optical properties of poled thin films of a guest–host system consisting in a charge transfer chromophore dissolved in poly bis(phenol A carbonate) matrix were studied by optical second harmonic generation and as function of chromophore content. The chromophores were oriented by the corona poling technique. The optical microscopy observations evidence a new mechanism of relaxation, which arises from the accelerated chromophore aggregation due to the heating which facilitates their diffusion.