Structural Characterization of Self-Organized Mono- and Multi layers of Poly[bis(2,2,3,3-tetrafluoropropoxy)phosphazene] at the Air/Water Interface

The layering transitions of mesomorphic poly[bis(2,2,3,3-tetrafluoropropoxy)phosphazene] induced by compression were found to result in the formation of stable multilayers directly at the air/water interface. This phenomenon is discussed with particular emphasis on its in situ structural characterization by Brewster angle microscopy, infrared spectroscopy, synchrotron grazing incidence X-ray diffraction, and X-ray reflectivity data. Compression of Langmuir monolayer is followed by layer-by-layer growth manifested by pronounced steps in the pressure/area isotherm. Grazing incidence X-ray diffraction reveals only one diffraction peak for the monolayer as well as for multilayers, which corresponds to an interchain spacing d = 12.3 A. The in-plane correlation length ξxy reaches an impressive 345 A for the uncompressed monolayer and 470 A for the tetralayer, implying a certain mesoscale order similar to a quasi-long-range one. After formation of the four-layer thick film the transition into a 3D crystalline tr...