HYDRATION NUMBER OF CALCIUM PALMITATE LB FILM DEPOSITED ON A PIEZOELECTRIC QUARTZ-CRYSTAL PLATE

The calcium palmitate monolayer formed from palmitic acid on calcium-c ontaining substrate can be examined regarding the study of hydration b y applying the quartz crystal microbalance (QCM) technique. Monolayers of calcium palmitate were deposited on piezoelectric crystal plate by the Langmuir-Blodgett (LB) technique. Analysis of complete conversion to calcium palmitate was performed by identification of its infrared spectra. The estimation of the hydration for the multilayered calcium palmitate is compared with the data of the multilayered calcium steara te in the literature. The QCM measurement for determining hydration nu mber is based on the results of McCaffrey, particularly employed in th e treatment of drying in vacuum (R.R. McCaffrey, S. Bruckenstein, P.N. Prasad, Langmuir 2 (1986) 228). In our experiments, the frequency cha nge of the oscillating quartz transducer for the skimmed calcium palmi tate also increased after drying in vacuum. Hydration behavior of the multilayered calcium palmitate LB film is discussed, and it was shown that the hydration of calcium palmitate exists as monohydrate, though its hydrophobicity is relatively a little low compared with that of ca lcium stearate, which has a longer hydrocarbon chain length. (C) 1998 Elsevier Science S.A. All rights reserved.