IN-SITU CHARACTERIZATION OF LANGMUIR-BLODGETT-FILMS DURING A TRANSFER PROCESS - EVALUATION OF TRANSFER RATIO AND WATER INCORPORATION BY USING A QUARTZ-CRYSTAL MICROBALANCE

Langmuir-Blodgett films of cadmium octadecanoate and other amphiphiles were transferred on a quartz crystal microbalance (QCM, 9 MHz, AT-cut) as a substrate with a vertical dipping method. Frequencies of the QCM substrate were followed with time in air, after the QCM was raised from the interface. The frequency was gradually increased (mass decreased) with time and reached the equilibrium in air, due to the evaporation of water incorporated between layers during a transfer process. From the time courses of these frequency changes at each dipping cycle, the transfer amount of dry LB films (W-1) the incorporated amount of water (W-2), and its evaporation speed (upsilon) could be obtained at the nanogram level. The LB films transferred on the rougher surface at the lower surface pressure with the higher lifting speed generally showed the greater amount of incorporated water (W-2) and the higher evaporation speed (upsilon), which means the disordered LB films were deposited on the substrate. When the well-oriented LB films were transferred on the substrate, a small amount of water was incorporated and the evaporation speed was small. Both W-2 and v values were also affected by chemical structures of amphiphiles: the amount of incorporated water (W2()) increased with increasing polarity of hydrophilic head groups, and the evaporation speed (upsilon) decreased with increasing alkyl chain length. Thus, a QCM system will become a useful tool to analyze LB films during the transfer-process in situ.