Sp. Weinbach et al., SELF-ASSEMBLED LANGMUIR MONOLAYERS AND TRILAYERS AT THE AIR FORMAMIDEINTERFACE, Journal of physical chemistry, 97(20), 1993, pp. 5200-5203
The spontaneous formation of highly crystalline two-dimensional films
of uncompressed long chain amide and carboxylic acid amphiphiles sprea
d on formamide has been demonstrated by grazing incidence X-ray diffra
ction. These results were compared to those found for the same amphiph
iles on water. The observed diffraction data Of C29H59CONH2 over both
water and formamide and those Of C29H59CO2H over formamide are strikin
gly similar, while those Of C29H59CO2H over water are different. Arach
idamide (CH19H39CONH2) over water subphase forms a unimolecular layer
with the molecules tilted by 18-degrees. Over formamide, the crystalli
tes are made up, at least in part, of three molecular layers, with the
molecules standing vertically. This was confirmed by X-ray specular r
eflectivity. These results are analogous to the well known, but as yet
unexplained, influence which solvent may have on the growth of polymo
rphic modifications of three-dimensional crystals.