Refine
Has Fulltext
- no (23)
Document Type
- Article (23)
Is part of the Bibliography
- yes (23)
Institute
Langmuir-Blodgett films of zinc 11,18,25-tri(tert-butyl)-4-sulfo-phthalocyanine (ZNPctSO3Na) have been deposited onto hydrophilic and hydrophobic silicon wafers. Y-type films were formed on both types of substrate, and the transfer ratio was very close to unity. The organization of the films on the molecular level was probed by X-ray specular reflectivity.
The molecular in-plane structure of uranyl arachidate Langmuir-Blodgett (LB) films formed at different subphase pH values was analysed by means of X-ray grazing-incidence diffraction. For multilayers formed at low subphase pH a reorganisation of the arachidic acid film structure is confirmed. At appropriate subphase pH values, reorganisation of the film structure, e.g. via the formation of three-dimensional crystallites, is prevented by the presence of the uranyl ions and by the subsequent introduction of conformational disorder (gauche defects) in the alkyl chains. The observation of a macroscopic flow-induced in-plane texture in these uranyl arachidate LB films has profound implications for the design of ordered, supramolecular structures by the Langmuir-Blodgett technique.
Study of gas transport through composite membranes with a stabilised Langmuir-Blodgett skin layer
(1995)
The Langmuir-Blodgett (LB-) technique is used to deposit molecular reinforced separation layers on porous polymer substrates resulting in composite membranes for gas separation. The adsorption of a polycation to the arachidic acid Langmuir layer and the subsequent transfer of the highly ordered and stabilised monolayer onto a polypropylene membrane (Cellgard 2400) yields a laminated separation layer combining the advantageous high degree of order of fatty acid films and the stability of thin polymeric films. X-ray reflectivity data of these films confirm the transfer of the assembled polymer layer together with the fatty acid monolayer and the formation of ordered Y-type LB-films. SFM pictures show a dense film without pinholes completely covering the porous support. Gas permeation measurements are used to study the transport process of different gases through the composite membrane.
Langmuir floating layers of two phthalocyanine derivatives, ytterbium bisphthalocyanine and tetra-tert-butyl nickel phthalocyanine, were investigated by means of compression isotherms, surface potential kinetics and Brewster angle microscopy (BAM) in order to study the influence of peripheral substituents on the structure and stability of these films and on their suitability for a subsequent transfer onto solid substrates. Specific substitutions that may lead to amphiphilic molecular units seem to play a key role in the development of well organised thin films prepared with this technique.
The formation of a Langmuir monolayer of an amphiphilic derivative of zinc phthalocyanine (Na[(ZnPcSO3)-S-t]) has been studied by means of surface potential technique and Brewster angle microscopy. The experiments were undertaken in order to understand the behaviour of this monolayer with a well-defined surface pressure isotherm. The floating film is described as a truly monomolecular layer formed by very rigid islands in which the phthalocyanine units tend to take on a preferential orientation with their planes perpendicular to the air-water interface, for high values of the surface pressure. (c) 2004 Elsevier B.V. All rights reserved
The complexation of highly ordered fatty acid monolayers with polyelectrolytes is expected to yield well- ordered Langmuir films suitable for the formation of Langmuir-Blodgett multilayers with improved long-term stability. Studies of the surface pressure-area isotherms and of the surface potential kinetics yield detailed information regarding the influence of these polymeric counterions on the monolayer properties. The injection of bivalent metal salts into the subphase after the complexation was used to improve the order and stability of the mono- and multilayers. The corresponding Langmuir-Blodgett films were investigated by means of X-ray reflectivity measurements and scanning force microscopy. The polyion complex multilayers show a strongly increased mechanical stability compared with films of fatty acid salts formed with bivalent metal ions. These structures are expected to be suitable as ultrathin separation layer for gas separation or ultrafiltration membranes.