LANGMUIR-BLODGETT-FILMS OF AMYLOSE ACETATE/DYE MIXTURES .2. LANGMUIR-BLODGETT MULTILAYERS OF MIXTURES OF AMYLOSE ACETATE AND A CHIRAL PARA-NITROAZOBIS[BENZENE] DYE

The structure of multilayers of a mixture of amylose acetate and a chiral nonlinear optical dye, a monoester of palmitic acid and 4-nitro-4'-[(3R)-hydroxypyrrolidino]-1,1'-azobis[benzene] (KMES16) has been studied. The monolayers of the mixed systems, consisting of domains of the dye in a matrix of amylose acetate, were transferred by the Langmuir-Blodgett technique onto solid substrates in the Z-type transfer mode. The structure of the multilayers was investigated by Fourier transform infrared spectroscopy, UV spectroscopy, and small-angle X-ray diffraction. The aliphatic chain of the dye molecule exhibits a remarkable orientation as revealed by infrared spectroscopy. These all-trans CH2 chains are tightly packed, and they have a specific orientation around the chain director. The dye fragment of the molecule appeared to be oriented at about 30-degrees with the surface normal, whereas the molecules are packed antiparallel in the lamellar crystals. From UV spectroscopy it was deduced that these crystals can be considered as H aggregates. After heating the multilayers and cooling, the IR spectra reveal a more well-defined structure with lamellar crystals, which also behave like H aggregates.