STRUCTURAL STUDY OF LANGMUIR-BLODGETT MONOLAYERS AND MULTILAYERS OF POLY(BETA-HYDROXYBUTYRATE)

In this study poly(beta-hydroxybutyrate) (PHB) was used as a spreading material to form LB monolayers at the air-water interface. Isotherms were found to show a transition at about 14 mN/m that is argued to be associated with a phase transition in the monolayer. Stable monolayers could be obtained at various surface pressures before as well as beyo nd the transition. Multilayers on substrates were investigated with FT -infrared techniques and were shown to have crystalline characteristic s. Hysteresis experiments confirm the occurrence of irreversible proce sses in the monolayer during compression. Transmission electron micros copy pictures clearly show the structural changes that appear with inc reasing stabilization surface pressure of the monolayer. At large area s PHB exhibits an expanded monolayer behavior. Under the influence of surface pressure PHB is argued to change into a crystalline structure and eventually to form a bilayer of helical molecules which is reflect ed in the shape of the isotherm. S-shaped stabilization curves are arg ued to be the result of an accelerated bilayer formation process, as i s confirmed by TEM pictures of this layer. Infrared external reflectio n spectroscopy of a PHB monolayer on the water surface gives clear ind ications that PHB already crystallizes at the air-water interface duri ng compression, thus confirming our theorem.