Photochromic Properties of New Dithienylethene Copolymer

Photochromic molecular switches can be important memory media for optical information processing and storage as long as their thermal stability and photo-fatigue resistance met certain criteria. Among many photochromic materials, heterocyclic diarylethenes have displayed desirable optical switching characteristics. Specifically, bisthienylethene (BTE)-based photochromic switches have demonstrated high sensitivity and rapid response as well as thermal- and photostability^1,2]. It has been shown that various BTEs can undergo ca.l0^4] cycles before significant evidence of fatigue^3]. It is important that molecules with otherwise improved switching characteristics retain this level of fatigue resistance. For example, the improved characteristics include that the absorption of close form of photochromic materials should be shifted to shorter wavelength region due that semiconductor laser shift to short wavelength are developing trend for high density information storage. Also, fatigue may be different in the solid state than in solution. In general, precedent photochromic polymers consisted of photochromic molecules either dispersed in a matrix or covalent grafted onto the polymer main chain.