STRUCTURAL STUDIES OF LANGMUIR AND LANGMUIR-BLODGETT-FILMS OF FUNCTIONALIZED SURFACTANTS

Structural studies of Langmuir and Langmuir-Blodgett films of function alized surfactants show that the organization of surfactants is strong ly dependent on cross-sectional match between the functionalized headg roup and the film-forming alkyl chain parts of the molecules. The orga nization of a particular functionalized surfactant with a slight cross -sectional mismatch between head and tail has been investigated by syn chrotron radiation in floating, monolayers and by atomic force microsc opy (AFM) in Langmuir-Blodgett films. The transfer process was accompa nied by an increase of the oblique unit cell area by 17% and by an inc rease of the average diameter of perfectly ordered domains from 3 nm t o approximately 10 nm. We have calculated a number of likely packing p atterns of alkyl chains and the lattice parameters of the Langmuir-Blo dgett films are found to be consistent with one of these packings. For comparison, the results of preliminary studies on a functionalized su rfactant with a severe cross-sectional mismatch between head and tail are presented, indicating that the tail is bent around the head group thereby preventing efficient packing of the alkyl chains.