PREPARATION AND CHARACTERIZATION OF COMPOSITE LB FILMS OF LIGNIN AND CADMIUM STEARATE

We report on studies of composite Langmuir films containing lignin (ex tracted from sugar cane bagasse) and cadmium stearate and their subseq uent transfer as Langmuir-Blodgett (LB) films. Pure lignin was found t o form non-monomolecular films at the air-water interface. Composite m onolayers of lignin and cadmium stearate with varying compositions hav e been obtained and characterized by surface pressure and surface pote ntial isotherm studies which essentially indicated the formation of a meta-stable composite monolayer at the air-water interface. Neverthele ss, these composite monolayers could be uniformly transferred onto sol id substrates under optimized deposition conditions. Transferred multi layer LB films were characterized by UV-vis and Fourier transform infr ared spectroscopy (FTIR), X-ray diffraction (XRD) and surface potentia l measurements. FTIR studies confirmed the transfer of lignin along wi th cadmium stearate. W-vis results revealed a layer-by-layer transfer of the composite monolayer. In the composite him, both cadmium stearat e and lignin were present as separate domains and the stacking order i n the cadmium stearate domains was found to be influenced by the incor poration of lignin, as evidenced from XRD. Surface potential measureme nts indicated a good film uniformity. (C) 1998 Elsevier Science S.A. A ll rights reserved.