Progress in molecular electrets

Some aspects of our investigations are: The light induced switching of self-assembling monolayers (SAM) and Langmuir Blodgett (LB) films containing azobenzenes is directly observed by the sensitive Kelvin Probe method, measuring the electret material. The ultrathin films are also examined by Scanning Probe Microscopy and IR spectroscopy, respectively. To optimise the switching process in the monolayer, pure and mixed films of different azobenzene thioles and n-alkylene thioles were prepared. Tne efficiency of E/Z isomerisation depends on the spacer length between azobenzene group and gold surface and the free volume in the film, tuned by the n-alkylene thiole fraction. An optimum was found in a mixed self-assembling film containing 33% 4-trifluoromethyl-4´-(1O-carboxy-decyloxy)azobenzene in a dodecane thiole matrix