Two different series of mixed Langmuir-Blodgett (LB) films with a controllable degree of polarity, deposited on mica, have been studied by wetting and surface force techniques. Both series contain 50% eicosylamine (EA). Films of one series consist of EA, arachidic acid, and docosandioic acid, while those of the other consist of EA, 1-eicosanol, and 1,22-docosandiol. Carboxylic acid groups give lower contact angles than hydroxy groups. Concerning the stability of the LB films in aqueous solutions, repeated exposure to a three-phase line and high salt solutions were found to cause breakdown. Surface force measurements on carboxylic acid-containing films show that films with a 0% (contact angle = 1 1 3 O ) and 25% (contact angle = 90°) content of diacid interact with a long-range (hydrophobic) attraction across water. No similar long-range attraction is observed for the 50% case (contact angle 65"). Surface force measurements also detected instabilities and imperfections of the films.

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