Poling and its relaxation studies of polycarbonate and poly(styrene-co-acrylonitrile) doped by a nonlinear optical chromophore

摘要

Spin-coated films of poly(bisphenol A carbonate) (PC) and poly(styrene-co-acrylonitrile) (SAN) doped by 4-(N,N-dimethylamino)-4'-nitrostilbene (DANS) were prepared,and their poling and depoling behaviors were investigated mainly by UV-visible absorption spectra and second-harmonic generation (SHG).The absorbance of DANS in the PC and SAN films proportionally increased with increasing its weight concentration up to 5 wt%,indicating homogeneous dissolution of DANS in the host polymers.However,above this concentration,heterogeneous structures due to DANS crystallites could be observed under a polarizing microscope.Poling of the films was performed using a triode corona discharging system.The maximum d coefficients were obtained at slightly lower poling temperature than the glass transition temperature of the corresponding dye-doped polymer.The KWW stretched exponential function could be fitted to the experimental temporal relaxation data of SHG for the SAN system.Relatively high long-term stability was observed for the PC system because of its relatively rigid backbone structure.