MONOLAYER AND MULTILAYER LANGMUIR-BLODGETT-FILMS OF CELLULOSE TRI-N-ALKYL ESTERS STUDIED BY TRANSMISSION ELECTRON-MICROSCOPY

The mono- and multilayer Langmuir-Blodgett films of cellulose tri(n-decanoate) (CTD) and cellulose tri(n-octadecanoate) (CTO) were prepared and studied with their fine structures and layer thicknesses by transmission electron microscopy. CTD was found to give a perfectly homogeneous monolayer film. The observed values of the film thickness L and the limiting area A indicated that the alkyl side chains are nearly fully extended and closely packed. The pi-A isotherm of this polymer (but not of CTO) exhibited a plateau region, which was interpreted in terms of a monolayer-to-bilayer transition. CTO also gave a homogeneous monolayer film, which was repeatedly transferred to give multilayer films with a homogeneous surface structure. The observed values of L and A suggested that the alkyl side chains in each layer are essentially extended, but in a somewhat poorly defined fashion as compared with those in thc CTD film.