The structure of mixed Langmuir films of the normal alkane C32H66 With different quantities of the normal alcohol C31H63OH Or the diol HO(CH2)(30)OH on pure water were determined in situ by applying surface-sensitive methods that include grazing incidence X-ray diffraction (GIXD) and infrared reflection-absorption spectroscopy (IRRAS) and by induced freezing of water drops. Random solid solutions were formed between the alkane and C31H63OH On the other hand, segregation of the two components was observed in the mixed systems of the alkane and HO(CH2)(30)OH. These findings suggest new ways for the design of hydrophobic surfaces bearing hydrophilic sites, which may be appropriate for epitaxial ice nucleation and cloud seeding purposes.