IN-SITU X-RAY-DIFFRACTION STUDY OF LANGMUIR-BLODGETT DEPOSITION

We have built a Langmuir-Blodgett (LB) deposition trough that mounts o nto a Huber 4-circle diffractometer, so that the LB substrate and the water are in the same closed, temperature-controlled environment. We h ave used this system to study Langmuir-Blodgett films just after trans fer using synchrotron X-ray diffraction. We were able to deposit from the L-2, L-2', S, and RII phases of a fatty acid monolayer, and observ e the same structures in the transferred monolayers. Three of these ph ases have not been observed before on a glass substrate. Once deposite d, the LB monolayer structure was not affected either by pressure chan ges in the water monolayer (when part of the substrate was still immer sed) or by the substrate remaining in contact with the water or not. T he structures were stable over time but changed irreversibly under the effects of radiation damage and temperature cycling. These results sh ow that the change from the structure observed on water to the final L B structure does not occur during deposition, but long afterward.