QUARTZ CRYSTAL DETECTOR FOR MICRORHEOLOGICAL STUDY AND ITS APPLICATION TO PHASE-TRANSITION PHENOMENA OF LANGMUIR-BLODGETT-FILMS

This paper shows that an AT-cut quartz crystal detector can be applied to the rheological study of thin films. Measurement of the resonant frequency and the resonant resistance of the quartz crystal was used to examine the mass change and the viscoelastic change of the coated films. This method was utilized to characterize the phase-transition phenomena of the Langmuir-Blodgett (LB) films of 1,3-dioctadecyl-rac-glycer-2-ol (2C18OH) which has two phase-transition points. The resonant frequency and the resonant resistance changes suggested that viscosity and mass increased at the first phase-transition point and elasticity decreased and viscosity increased at the second phase-transition point. The transverse wave amplitude of the fluid film surface was estimated as a ratio against the shear vibrating amplitude of the quartz crystal surface by immersing the film-coated quartz in water and 50 wt % sucrose solution to clarity the effect of these contact liquids. The ratio was determined to be 88 % for the 50-layer 2C18OH LB films above the second phase-transition temperature.