Abstract
Octadecanol monolayers at the air/water interface are studied by grazing incidence x-ray diffraction. At low lateral pressures one observes the diffraction patterns inherent to the next-nearest neighbor tilt of the molecules. The unit cells are found to be distorted at both low (6 °C) and high (33 °C) temperatures due to tilt of the molecules and ordering of their backbones. Unexpectedly, at an intermediate temperature of 22 °C, the unit cell remains hexagonal in the water plane, despite the tilt of the molecules. This behavior is treated in terms of hydrogen bonding with the water molecules and does not imply the existence of a separate phase. Our diffraction study also does not show any indication of a phase transition S*–L2* corresponding to the singularities in the isotherms within the tilted phase. The tilting phase transitions from untilted phases S and LSII seem to be continuous, since the transition pressures obtained by extrapolation of the tilt angle to zero tilt coincide with the ones determined by Brewster angle microscopy.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.