Photo-induced reaction of dye in polymer media—IV. Kinetics of photoisomerization Z → E of Aberchrome 540 in polymer matrices

✍ Scribed by Manit Rappon; Kalsom Mohd Ghazalli

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 653 KB
• Volume: 31
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(95)00093-3

✦ Synopsis

A photochronnc fulgide known as Aberchrome 540 is amber in its ring-opened Z-form [(Z)-a-(2,5-dimethyl-3-furylethylidene) (isopropylidene) succmic anhydrlde]. It is photoisomerized at I > 300 nm to give another ring-opened amber E-form which subsequently undergoes a conrotatory ring closure to give the red C-form [7,7a-chhydro-2,4,7,7,7a-pentamethylbenzo [b] furan-5,Gdicarboxylic anhydride]. The kinetics of Z 4 E is obtained by fitting a consecutive kinetic model to the experimental data of Z 2E 4C, using the known k, from previous experimental work. Thin films of dye, dispersed in polymer matrices by the solution-cast technique. have been used in this investigation

The reactlon is studied at 303-338 K by monitoring the absorbance at A,, of 493 nm of the final product (C) formed at various irradiation times. The polymer matrices are poly(styrene), poly(p-t-butyl styrene), poly(viny1 acetate), and poly(n-butyl methacrylate).

The magnitudes of the calculated rate constants, k,s and the apparent (thermal) activation energies, E,s appear to be under the influences of the available free volume at the dye sites. molecular motions of media and &polar interactions.