INVESTIGATION OF THE VERTICAL MOLECULAR-EXCHANGE IN A COMPLEX ORGANICMULTILAYER SYSTEM

A vertically stacked Langmuir-Blodgett (LB) multilayer system composed of undeuterated and deuterated Cd-stearate bilayers being separated b y bilayers of the amphiphilic copolymer MSA22 has been investigated. S pecular and off-specular scattering curves were collected at room temp erature and under thermal annealing up to 85 degrees C. The neutron me asurements have been performed on the new neutron reflectometer ADAM a t the Institute Laue-Langevin at Grenoble for the first time. Already at room temperature the intermixing between deuterated and non-deutera ted molecules amounts to 20% and increases during thermal annealing. I n contrast to recent measurements of samples without copolymers the th ermally induced interdiffusion is significantly reduced now, unfortuna tely at the cost of losing the lamellar order. The evaluated activatio n energy of molecular exchange confirms our recent results. X-ray and neutron specular reflectivity curves cannot be interpreted solely by t he Parrat formalism. Under relaxed condition of experimental resolutio n the off-specular scattering dominates the reflectivity curves even f or large q(z). On the other hand, the evaluated q(z)-dependence of the resonant-diffuse scattering reveals that the height-height correlatio n of interfaces roughness is the main origin of diffuse scattering in such multilayers. (C) 1998 Elsevier Science B.V. All rights reserved.