CIS-TRANS THERMAL-ISOMERIZATION RATES OF BOUND AND DOPED AZOBENZENES IN A SERIES OF POLYMERS

A series of high-T-g side-chain azo aromatic polymers and small molecu lar weight azobenzenes dissolved in polymers were cast as thin films a nd subjected to a pump/relax procedure to analyze the thermal cis-tran s isomerization behavior of the azo groups. All samples exhibit a fast isomerization process due to strained cis isomers trapped below the g lass transition temperature of the film, followed by a slower isomeriz ation process which can be analyzed by a monoexponential decay. Therma l isomerization rate constants are found to depend on the spectral typ e of the chromophore and type of attachment to the polymer backbone an d, less importantly, on the glass transition temperature and the cryst alline order of the polymer.