The functional specificity of polymer monolayers can be controlled through molecular architecture. A series of preformed polymers containing hydrophobic side chains of various chemical compositions has been investigated in order to assess their interfacial properties at diffusion barriers. Fourier transform infrared and neutron reflectivity studies of multilayered Langmuir-Blodgett films of cadmium arachidate and its deuterated analogue indicate that rapid interdiffusion occurs at elevated temperatures (85 °C). Results also indicate that the extent of this interdiffusion can be controlled through the introduction of a polymer bilayer at the interface and can be varied depending on the chemical structure of the side chain. © 1992, American Chemical Society. All rights reserved.