2-D lattice constant control in LB films containing pyrrole

Pyrrole (Py) was used as a spacer molecule and we studied the structural phase transition of two-dimensional (2-D) crystal lattice of the arachidic acid (C-20) Langmuir-Blodgett films using atomic force microscopy. It was found that when quantity of Py in the Langmuir-Blodgett film is increased, the molecular occupation area of C-20 molecules increased and that the crystal lattice changed as follows : ''oblique --> hexagonal --> rectangular''. These structural phase transitions were compared with the computer simulation using 3-D model of the molecules by molecular mechanics.