WETTABILITY, SURFACE-MORPHOLOGY, AND STABILITY OF LONG-CHAIN ESTER MULTILAYERS OBTAINED BY DIFFERENT LANGMUIR-BLODGETT DEPOSITION TYPES

Methyl arachidate Langmuir-Blodgett multilayers, built up by X-, XY- a nd Y-type transfers, are characterized by means of contact angle measu rements, and optical and atomic force microscopy under ambient conditi ons. Contact angle investigation shows identically high hydrophobicity of the surfaces produced by X- and Y-type depositions, implying molec ular overturning during the X-type transfer. This overturning has not been detected in the previous X-ray study of small numbers of deposite d fatty acid methyl ester monolayers. Molecular resolution AFM images of thin methyl arachidate LB films show a disordered surface structure . Scanning over larger film regions reveals a considerable difference in the surface morphology, corresponding to pure and mixed-type LB tra nsfers. Reorganization of the multilayers occurs under ambient conditi ons in both cases. Larger aggregates, steps, and irregular islands are found with Y-type deposition. Ester LB films studied in an aqueous en vironment rearrange more easily than those stored in air. AFM imaging of the ''contact line corrosion'' of the multilayers shows a collectiv e depletion of the whole LB film from the substrate at the wetting per imeter. The instability of the ester mono- and multilayers is explaine d on the basis of the intra- and interlayer molecular interactions wit hin the spread and the deposited films, and by their weak adhesion to the substrate.