Optical properties and dynamics of a photochromic bisthienylethene in solution and in a polymer film

Optical switching dynamics and fatiguewere investigated for a photochromic molecular switch, bis(5-pyridyl-2-methylthien-3-yl)perfluorocyclopentene (PMTFC). Femtosecond transient absorption was measured using 270 nm pump and broadband visible probe pulses for samples in ethanol solution and as a dispersion film of poly(butyl acrylate-co-acrylic acid). The optical switching occurs in less than or equal to 3 ps in both cases. The spectral evolution observed in solution within 20 ps is absent in the film, suggesting that the switching dynamics are sensitive to the molecular environment. PMTFC in the copolymer film demonstrated evidence of fatigue after similar to 1500 complete cycles of optical switching. (C) 1998 Published by Elsevier Science B.V. All rights reserved.