MOLECULAR SWITCHING IN PHOSPHOLIPID-AZOBENZENE MIXED MONOLAYERS BY PHOTOISOMERIZATION

Molecular switching in phospholipid and azobenzene mixed monolayers on a water surface was examined by Maxwell displacement current (MDC) me asurements coupled with surface-pressure measurements. MDC and thermal ly stimulated current (TSC) measuring techniques also examined molecul ar switching in these monolayers on a solid substrate. It was found th at the molecular aggregation of pure azobenzene monolayers in both Lan gmuir (L) and Langmuir-Blodgett (LB) films is reduced by the introduct ion of phospholipids possessing unsaturated long alkyl chains (DOLPC) or saturated long alkyl chains (DPPC), and that the cis-trans photoiso merization in a mixed monolayer is accelerated. However the contributi on of the two kinds of lipids in mixed monolayers was found to be diff erent. The temperature dependence of charge induced across these mixed LB films, due to photoisomerization, corresponded well with that of o ctyl-4'-(5-carboxyl-pentamethyleneoxy)-azobenzene (8A5H) LB films. Fin ally it was concluded that the cis-state 8A5H molecules, in monolayers , return to the trans-state during heating. (C) 1998 Elsevier Science S.A. All rights reserved.