Photoisomerization of merocyanine 540 in polymer–surfactant aggregate

Photoisomerization of merocyanine 540 (MC540) in a polymer– surfactant aggregate is studied using picosecond time resolved emission spectroscopy. The aggregate consists of the polymer, poly(vinylpyrrolidone) (PVP) and the surfactant, sodium dodecyl sulphate (SDS). With increase in the concentration of SDS in an aqueous solution of MC540 containing PVP, the emission quantum yield and lifetime of MC540 increase markedly. This indicates marked retardation in the nonradiative photoisomerization process of MC540, when it binds to the polymersurfactant aggregate. The critical association concentration of SDS for binding to PVP has been found to be 0,5 mM. This is about 16 times lower than the CMC of SDS in pure water (8 mM).