Photo-induced reaction of dye in polymer media—III. Kinetics of photocolouration of aberchrome 540 in polymer matrices

✍ Scribed by Manit Rappon; Kalsom Mohd Ghazalli

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 736 KB
• Volume: 31
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(94)00164-2

✦ Synopsis

Ahstract-14berchrome

540 is a photochromic fulgide. It is amber in its ring-opened E-form [(E)-a-(2,5dimethyl-3-furylethylidene) (isopropylidene) succinic anhydride]. Upon irradiation with U.V. light at 1 > 300 nm, the dye undergoes a conrotatory ring closure to give the red C form [7,7a-dihydro_2,4,7,7,7apentamethylbenzo [b] furan-5,6-dicarboxylic anhydride]. The kinetics of the photocolouration (from E to C form) of the dye dispersed in a number of polymer matrices has been investigated in the temperature range 298-338 K. The kinetics is followed spectrophotometrically by monitoring the amount of C form at its &,, of 493 nm. The polymer matrices are poly(styrene), poly(p-t-butyl styrene), poly(methy1 methacrylate), poly(n-butyl methacrylate) and poly(viny1 acetate). The first-order plot of the results of each run shows two distinct linear lines whose slopes have led to the extraction of the pseudo first-order rate constants k, and k,, at the beginning and toward the end of the reaction times, respectively. The values of k, are not shown, since for each kinetic run, the line covers so few data points to make k, value meaningful. Only k, s and the corresponding overall thermal activation energies are presented. The kinetic results suggest the plausible presence of two conformers of the reactant in its ring-opened E form.