Photochromic cooligomers from pyridazinespirodihydroindolizine and styrene

Abstract

New cooligomers 5 of styrene and 4-vinylpyridazine have been prepared by the controlled free radical polymerization technique. The addition of spirocyclopropene has led to cooligomers 6 in which the pendant pyridazine subunits are transformed into photochromic spirodihydroindolizines. Characterisation by NMR and SEC was carried out with 5 and 6. Molecular masses (M) of 5 and 6 have been found to be in the range of oligomers. Studies by UV-VIS-spectroscopy have shown the photochemical properties of 6 and of the reference compound 3. The absorbance of 6 is similar to that of 3. The fatigue resistance (Z 80 =4-10) of the cooligomers 6 shows 6 to be more stable than 3. The half life of the cooligomers 6 was found to be (100±20 s).