X-RAY STUDY OF LB MULTILAYERS OF CADMIUM SOAPS IN THE VICINITY OF THE BREAK UP POINT

Temperature dependent SAXS measurements were carried out on multilayers of two different salts, cadmium palmitate (hexadecanoate) and behenate (docosanoate). The pattern characteristic of layer structure disappears at a transition temperature well below the bulk melting point in both cases. Examination by means of optical microscopy shows that the LB films break up at a temperature close to this transition. Measurements in its vicinity demonstrate that over a certain temperature range just below the transition a second set of peaks arises in the diffraction pattern. During this transition region of about 3-degrees-C width two d-spacings for both salts were found, suggesting the simultaneous existence of two different structures for each component at the same temperature.