STRUCTURAL-ANALYSIS OF MIXED LB MULTILAYERS AND SUPERLATTICE FILMS

Multilayers of Y-type bilayers of pure and mixed Ba-salts of stearic, arachidic and behenic acid on solid supports were prepared by classica l Langmuir-Blodgett technique and analyzed by X-ray powder diffraction . Various systems composed of repeats (A(n)B(m))(x) of n bilayers of f atty acid salt A followed by m bilayers of fatty acid salt B were prep ared. Of the obtained mixed multilayers the (A(n)B(m))(x) system of on e bilayer Ba-behenate to one bilayer Ba-stearate (n,m = 1), two bilaye rs Ba-behenate to two bilayers Ba-stearate (n,m = 2) and six bilayers Ba-behenate to six bilayers Ba-stearate (n,m = 6) exhibited superstruc tural diffraction patterns, which were also found in the (A(n)B(m))(x) system of four bilayers Ba-behenate to two bilayers Ba-arachidate (n = 4, m = 2). The multilayer system of twelve bilayers of Ba-behenate t o 12 bilayers of Ba-stearate (n,m = 12) exhibited only the diffraction pattern of a mixed structure of two separate layer systems, The exper imental results are compared with calculated diffraction patterns, obt ained by electron density models of the multilayered systems. Differen ces between experimental and calculated diffraction patterns are discu ssed. (C) 1997 Elsevier Science S.A.