Studies on fluorescent PVA + PVP + MPDMAPP composite films

Polymer blends along with 1-(4-methylphenyl)-3-(4-A/,A/, dimethyl amino phenyl)-2-propen-1-one (MPDMAPp) NLO-chromophore-doped composite films were prepared by solvent casting method using DMF. The optical properties were studied using UV-visible, refractive index, steady state fluorescence, and fluorescence microscopic imaging techniques. The UV-vis absorption spectra showed three absorption bands and were assigned to localized n -π&z.ast;, n - π&z.ast; inter band, and π - π&z.ast; transition of charge transfer groups. The observed changes in the absorption peak, edges, and intensity with dopant concentration are understood based on charge transfer complex (CTC) formation. The refractive indices of the composite films varied from 1.4937-1.5398 for red and 1.5165-1.5516 for green light respectively. The steady state fluorescence data showed both emission peak wavelengths and intensity changes with MPDMAPP doping level in blend. The fluorescence anisotropy (r) variations in the composite films indicate the suppressed molecular motion of MPDMAPP in the solid composite film. The fluorescence microscopic image of these composite films showed that the films are photochromatic in nature. These modified properties are thought to be due to the charge transfer upon excitation from the donor to the acceptor connected through benzene ring and CTC formation.