Phase transitions and structures in Langmuir-Blodgett films

In order to reveal phase transitions and structures of organic ultra-thin films, we made temperature dependence measurements of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) on both Langmuir-Blodgett (LB) films and powder of manganese-arachidate salt. Unlike pure arachidic acid, DSC measurements of the manganese-arachidate powder showed two-phase transitions, i.e., the main transition and a new transition, or pretransition. XRD measurements of the LB films confirmed the two-phase transitions, and three phases, namely, a lamellar phase with a certain tilt, a lamellar phase without tilt, and an ordered fluid phase with melted alkyl-chains. The findings indicate that the phase behavior plays a key role in the fabrication mechanics of LB films of transition metal-fatty acid salt, such as the temperature control during the monolayer formation and annealing processes.