X-ray reflectivity study of polymer assembly at air-water interface

X-ray reflectivity (XR) measurements were carried out for amphiphilic diblock copolymer monolayers on water surface. From XR data, the layer thickness, and surface and interface roughnesses could be determined as a function of surface pressure. The XR experiments were performed using an 'Air-Water Interface X-ray Reflectometer' with conventional X-ray source (Cu target) in our laboratory. LB trough was equipped to the reflectometer: so the in situ measurements could be carried out for spread monolayers on water surface at different surface pressures. Kiessig fringes were observed for specular measurement for amphiphilic diblock copolymer, poly(alpha-methylstyrene)-poly(decyl 4-vinylpyridine) (P(alpha MSt)-b-P(4VP-C10H21I)) monolayers on water surface. It was observed that the thickness of the monolayer became thicker with increasing surface pressure. By curve fitting for the data obtained for the monolayer at surface pressure of 37 mN m(-1), the thicknesses of P(alpha MSt)(50) and P(4VP-C10H21I)(50) layers was determined to be 21 and 22 Angstrom, respectively. Because the chain length of P(alpha MSt)(50) is calculated to be 126 Angstrom in all-trans conformation, it was indicated that the molecules did not get aligned even when they were pressed to become such a dense state. (C) 1998 Elsevier Science Limited. All rights reserved.