The Determination of the Coloring Centers through Casting (C-DCPF )5% - (PMMA) Film and New Optical Comparative Studying With its E-isomer.

Abstract

Filmsof 5% E-dicyclopropyl-methylene-(2,5-dimethyl-3-furylethylidene-succinic anhydride (E-DCPF) doped in PMMA polymer films, [E -(DCPF ) -(PMMA) films], were prepared by casting method and then were irradiated with UV light (360 nm) for different exposure time (2-38 min). The color of the films turned to deep pink after 38 min. The photo-bleaching time was 670 min. The absorbance spectrum was studied in the range from 190 nm up to 650 nm, where that spectrum showed four peaks. The onset one was related to the photo coloration effect at 516.44 nm,where it was increased in height and decreased in its width by the increasing of the exposure time of UV-Irradiation . The other three peaks were at 363 nm, 272.85 and 218 nm respectively. The spectra have an isosbestic point at (417 nm).The optical properties of the films were investigated using the spectrophotometric measurements of both the transmittance and reflectance in the spectral range from 400 to 1500 nm . Both the refractive index, n, and the absorption index, k, were calculated before and after coloration.For the first time ;the parameters of the molar extinction coefficient (ε molar )[oscillators energy (E 0s ), oscillator strength (f), electronic dipole strength (q 2 ) and the concentration of the coloring centers were evaluated. The analysis of the absorption coefficient (α) revealed three indirect transitions and only one direct transition for photo -bleached films ,while two indirect transitions and only one direct transition for colored films . …………………………………………………………………………………………………….... Introduction:-Dicyclopropyl fulgide (DCPF) has attracted a great attention because it is an important one of the organic photochromic compounds. These compounds are considered as promising candidates in photoswitchable system which require high reversibility [1][2][3][4][5][6][7][8][9][10][11] and in optical memory devices which depending on non -destructive readout stability [5][6][7]. Through all photochromic candidates; Fulgides showed a reversible photochromism with minimum photochemical fatigue [2,8], thermal stability [9] and nondestructive readout stability .The photochromism of fulgide occurs between the open E-isomer and the photocycle colored form(C-isomer) [2,[5][6][7]. The molecular structure for E&C (isomers) of DCPF is shown in Fig.1(a)