ELUCIDATION OF MULTILAYER GROWTH OF AMPHIPHILES ON LIQUID SURFACES

The crystalline properties of the amphiphilic systems N-methylarachida mide (NM) and of N,N'-dimethyldocosanediamide (NND) in the uncompresse d state at 5 degrees C on surfaces of water and liquid formamide were studied by grazing incidence synchrotron X-ray diffraction (GID). On w ater, the amphiphile NM forms a crystalline monolayer. On formamide, N M behaves differently. One h after deposition on the liquid surface, G ID patterns indicated coexistence of two different crystalline monolay er structures. Three h later, a crystalline bilayer had formed. The fu ndamental question as to whether the interlayer growth took place in t he liquid subphase or in the air was elucidated with the help of the t ailor-made additive N-benzylarachidamide (NB). Addition of 10% of NE i n the spreading solution yielded only a monolayer. From this result we conclude that bilayer growth of pure NM must occur from the liquid si de. It also helps to establish a similar interlayer growth mechanism f or the trilayer formation of pure arachidamide on liquid formamide.(1) The amphiphile NND behaved differently from NM as it formed a crystal line monolayer on both water and formamide liquid surfaces.