Polymerization of eicosenoic acid and octadecyl fumarate in Langmuir-Blodgett multilayers

UV-induced reaction kinetics of dilinoleoylphosphatidylethanolamine monolayers

The UV-induced reactivity of dilinoleoylphosphatidylethanolamine (DLiPE) Langmuir and Langmuir-Blodgett films has been studied by in situ measurements of the changes in the mean molecular area, UV-vis and Fourier transform infrared spectroscopy, and atomic force microscopy (AFM). Optimum orientation and packing density of the DLiPE molecules in the monolayer were achieved by adding uranyl acetate to the subphase. A first-order reaction kinetic model was successfully fitted to the experimental reaction kinetics data obtained at a surface pressure of 30 mN/m. Topographical studies of LB films by AFM were performed on bilayer structures as a function of subphase composition and UV irradiation time. The orientational effect of the uranyl ions on the monolayer molecules was observed as an enhanced homogeneity of the freshly prepared monomeric LB films. However, the long-term stability of these films proved to be bad; clear reorganization and loss of a true monolayer structure were evidenced by the AFM images. This instability was inhibited for the UV-irradiated films, indicating that the UV irradiation gave rise to a cross-linked structure.

Preformed polymers for Langmuir—Blodgett films

Langmuir-Blodgett (LB) films of simple molecules are usually fragile and this has prompted the study of polymeric lb films. Films have been prepared successfully from preformed polymers that are derivatives of various vinyl-maleic anhydride alternating copolymers. By using a computer-controlled trough polymeric films containing several hundred layers have been prepared. Low-angle X-ray scattering studies indicate that the films have a regular layer structure. By using a specially constructed trough, multilayers have been prepared in which alternate layers are polymeric, LB films prepared from polymers containing appropriate vinyl groups can be crosslinked by ultraviolet light or an electron beam (EB). This not only further stabilizes the films and renders them insoluble, but also allows patterns to be ‘ drawn ’ in the films. Films of these polymers have been used as submicrometre EB resists. Films suitable for second harmonic generation and electro-optic modulation have been prepared. Some further applications of polymeric LB films are outlined.