Abstract: The order-disorder transition in“Reversed Duckweed”type polymeric LBfilmwas investigated by temperature-dependent infrared transmition and X-rav diffraction. Threesteps of melting process were obtserved :the first and second steps were reversible transitionscorresponding to the disorder of the alkyl chains in each layer,and the layer structure wasmaintained;the third was an irreversible transition corresponding to the melting of the two-dimension system,and the layer structure was damaged during this phase transition process.

Key words: Polymeric LB film, Order-disorder transition, Temperature-dependent IR, Tem-perature-dependent low-angle X-ray diffraction