Investigation of the structure of polymer diacetylene Langmuir-Blodgett films

Abstract The structure of Langmuir-Blodgett (LB) diacetylene films CH3‒(CH2)11‒C≡C‒C≡C‒(CH2)8‒COOCd1/2 (DA1) and CH3‒(CH2)20‒CO2‒CH2‒C≡C‒C≡CH2OH (DA2) was studied by X-ray small angle scattering and electron diffraction methods prior to and upon their polymerization. It has been established that Langmuir films have layer packing. The periods of the constituent layers were determined as 58 A (for DA1) and 69 A (for DA2). This indicates the existence of a vertical bilayered packing of molecules. It has also been established that polymerization of LB diacetylene films due to the action of UV irradiation does not change the layer thickness appreciably and the structural rearrangement reduces to a slight redistribution of the electron density along the molecules which is explained by a break of the triple bonds during the UV irradiation.