Polymer Langmuir-Blodgett Research Articles

Selectivity of toxic and acid gases over methane and nitrogen in Langmuir-Blodgett films

Composite membranes for gas separation were fabricated by depositing polymeric Langmuir-Blodgett (LB) films on porous support membranes. By bridging over the pores of the porous support, the polymeric LB film acted as a selective barrier to gas diffusion. The gas selectivity of the LB films was demonstrated by measuring pure-component permeabilities as a function of temperature. LB composite membranes were selective for hydrogen sulfide (a toxic and acid gas) and carbon dioxide (an acid gas) over methane and nitrogen. Carbon dioxide selectivities were reduced by a slow reaction of H 2S with the LB film. Grazing angle infrared reflection-absorption spectra (IRRAS) of separate films on aluminized glass slides showed irreversible disordering of the hydrocarbon side groups of the polymer at 35 °C. Disordering improved the selectivities of H 2S and Co 2 relative to CH 4 and N 2.

Photo‐reversible Reaction in Polymer Langmuir‐Blodgett Films

AbstractPreparation of photoreactive Langmuir‐Blodgett (LB) films was carried out using polymers/oligomers prepared from long‐chain dialkyl esters of di‐and tetra‐olefins and having cyclobutane rings in the main chain. These polymers/oligomers formed stable monolayers on a water surface when mixed with arachidic acid. These monolayers could be deposited onto a substrate successfully forming Y‐type films. The oligomer LB films were polymerized on irradiation. The polymer LB films showed a photo‐reversible process between polymers and oligomers, depending on wavelength of the irradiating light. On the basis of spectral data and molecular weight change, this behaviour was found to be caused by cleavage and formation of cyclobutane rings.

AFM investigation of microstructures of diacetylene Langmuir-Blodgett films

We have taken images of unpolymerized monolayers of diacetylene Langmuir-Blodgett (LB) films using an atomic force microscope (AFM). The arrangement of molecules of the first layer should not always be completely periodic and the tilting angle of molecules is different from place to place. On the other hand, it is shown that the macroscopic molecular orientation of polymerized diacetylene LB films can be improved by applying a pulsating electric field to a monolayer at the air-water interface.

Preparation of Polymer Langmuir-Blodgett Multilayers Containing Axially Chiral Binaphthyl Group

Preparation of Polymer Langmuir-Blodgett Multilayers Containing Axially Chiral Binaphthyl Group

Control of surface chemical structure and functional property of Langmuir-Blodgett film composed of new polymerizable amphiphile with a sodium sulfonate

Sodium 1,2-bis[[[16-(acryloyloxy)hexadecyl]oxy]carbonyl]ethane-1-sulfonate (2AC 16 SNa) Langmuir-Blodgett (LB) film transferred to a polystyrene film by Langmuir-Blodgett techniques had a bilayer lamella structure with a high degree of lamella-plane orientation. The monomeric LB film was polymerized to stabilize the surface chemical structure (hydrophilicity or hydrophobicity). The highly oriented bilayer lamella structure was retained even after polymerization. The polymerized LB film with a sulfonic group orienting normal to the LB film surface showed an excellent blood compatibility

Polymer Langmuir-Blodgett films containing photofunctional groups. 2. Electron-transfer quenching in polymer Langmuir-Blodgett films containing carbazole chromophore

N-Vinylcarbazole (Cz), being nonamphiphilic, has been introduced into Langmuir-Blodgett (LB) film as a comonomer of N-dodecylacrylamide (DDA) which has an excellent ability to form monolayer and B multilayer. The spreading behaviors of the DDA/Cz copolymers with various Cz contents on a water surface were investigated by a measurement of the surface pressure-surface area isotherms

Thermostability of polymeric langmuir–blodgett films

Communication: LB films stable against desorption up to 250°C have been produced from prepolymerized polyurethanes, polyimides and polyamic acid and studied using optical reflection, microscopy, ellipsometry, ESCA, FT‐IR and small angle X‐ray scattering (SAXS). Due to their stability, the materials could be used to prepare multilayer films or as matrices for dyes opening up applications in optics.

Metal-insulator-semiconductor structure with a polymerized Langmuir-Blodgett film of a styrene functionalized surfactant

Metal-insulator-semiconductor structures were studied using polymerized films of di- n-octadecylmethyl( p-vinyl) benzylammonium chloride (DOVAC) as the insulator. DOVAC layers were deposited onto a p-type silicon wafer by means of the Langmuir-Blodgett technique and polymerized by UV radiation. High frequency capacitance-voltage ( C-V) measurements showed accumulation, depletion and inversion regions. The dielectric thickness d/ε r of a polymerized DOVAC monolayer was measured to be 0.6 nm. The effective fixed charge density at the insulator-silicon interface was of the order of 10 11 electronic charges cm −2. An abnormal hysteresis, probably caused by charge trapping at the silicon-insulator interface, was observed in the C-V curves. A field effect transistor based on a polymerized DOVAC film was fabricated.

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.

Studies on Langmuir‐Blodgett multilayer formation from preformed poly(N‐alkylacrylamides)

AbstractThe spreading behaviour of preformed poly(N‐alkylacrylamides) having hexyl (PHA), octyl (POA), decyl (PDA), dodecyl (PDDA), tetradecyl (PTDA), hexadecyl (PHDA), and octadecyl (PODA) substituents on a water surface, and the properties of the Langmuir‐Blodgett (LB) films deposited from these polymer monolayers were investigated. The surface pressure (F)‐area (A) isotherms of the polymer monolayers were changed by the chain length of the substituents and the subphase temperature. The optimum conditions for the formation of a stable condensed monolayer from the polymer series of similar molecular weight (c. 4 × 103) were found when the alkyl substituent was the dodecyl group (i.e. PDDA) and the subphase temperature was 19°C. The condensed monolayers of PDA, PDDA, and PTDA could be transferred successively on to solid supports such as quartz slides, giving the Y‐type uniform polymer LB films. The successive uniform depositions of PDDA monolayer up to 320 layers were confirmed by a relationship between the absorbance at around 200 nm due to carbonyl group and the number of layers deposited. The thickness of PDDA monolayer in the LB film was 1.72nm which agrees with the length of the dodecylamide substituent. F‐A isotherms, FTIR, and X‐ray diffraction measurements support that the polymer main chains are laid horizontally on the water surface and the alkyl substituents are oriented perpendicular to the chain in the condensed monolayer (see Scheme 1).

Determination of the elastic constants of a polymeric Langmuir-Blodgett film by Brillouin spectroscopy

Brillouin scattering experiments have been performed and theory developed on polymeric uniaxial Langmuir-Blodgett films (poly(γ-methyl- d-glutamate-co-γ-n-alkyl- l-glutamate)) with their preferred molecular axis in the plane of the film. Surface acoustic modes, guided modes and bulk modes were obsersed. Samples with from 10 to 560 molecular monolayers were measured and the elastic constants were found to be of hexagonal symmetry and not to depend on the film thickness. The whole set of elastic constants of the Langmuir-Blodgett films was determined from the spectra: c 11 = 4.74 GPa, c 33 = 10.8 GPa, c 12 = 3.43 GPa, c 13 = 3.57 GPa and c 44 = 0.91 GPa.

Energy transfer and excimer formation in layered polymer films prepared by the Langmuir-Blodgett technique

Langmuir-Blodgett (LB) polymer films containing various kinds of chromophores have been prepared from a preformed polymer, poly(vinyl octal). The fluorescence properties, energy transfer and excimer formation in the layered structure have been investigated to elucidate the photophysical characteristics of polymer LB films. The built-up film exhibits no excimer emission even at high concentrations of chromophores. Efficient energy transfer takes place between neighbouring layers, and the transfer process can be controlled by the sequence and the spacing of the layers. This behaviour is attributed to the uniform distribution of chromophores and low thickness of the polymer LB film.

Langmuir-Blodgett films of preformed copolymers of N-alkylacrylamides with vinylcarbazole

Copolymers of N-dodecylacrylamide and N-octylacrylamide with N-vinylcarbazole give stable monolayers on pure water. The copolymer monolayers can be transfered onto solid supports successively using the Langmuir-Blodgett (LB) method. The photoinduced electron transfer from carbazole in the copolymer monolayer to a viologen acceptor in the adjacent monolayer at the same interface was studied using the emission quenching method. It is concluded that the carbazole chromophore can be incorporated into the polymer LB film as a comonomer of alkylacrylamides which have excellent monolayer formation ability. This method is useful for obtaining a photofunctional polymer LB film.

Radiation Chemical Reaction and Submicron Pattern Fabrication on 10,12-Pentacosadiynoic Acid LB Films Using X-Ray Irradiation

X-ray induced polymerization of 10,12-pentacosadiynoic acid (PDA) Langmuir-Blodgett (LB) films has been studied in relation to the molecular density or arrangement for use in X-ray resists. Two typical PDA LB films of different molecular densities were polymerized to form different polymer LB films by X-ray irradiation. The low-density PDA LB films (A type) were more sensitive than the high-density PDA LB films (B type) when X-ray was irradiated in helium atmosphere and the polymerization was caused topochemically on A-type film but not on B-type film. Decomposition of polymerized films was observed by excessive irradiation of X-ray for A-type film, but not for B-type film. Using both types of PDA LB films, 0.4 µm patterns could be fabricated by X-ray exposure.

Photopolymerization in a Langmuir-Blodgett film of an amphiphilic cyclodextrin derivative containing a diacetylene group

A Langmuir-Blodgett (LB) film of a novel amphiphilic β-cyclodextrin derivative containing a diacetylene group in the hydrophobic part was prepared, and its photochemical reaction was investigated. Intermolecular photopolymerization in the LB film was observed using UV-visible spectroscopy and gel permeation chromatography. The polymerized LB film was insoluble in organic solvents such as tetrahydrofuran and chloroform, and was immobilized on a glass plate.

Photopolymerization of monomolecular films with diacetylene bonds on an aqueous subphase

The photoreactivity of monomolecular films of a diacetylene derivative (10,12-pentacosadiynoic acid (PDA)) under UV irradiation has been investigated at the air-water interface. With decreasing molecular area, the reactivity of the Langmuir film (the Langmuir film is the monomolecular film on an aqueous subphase) decreased, and the colour transition of the Langmuir film polymerized by the UV irradiation was from blue to red. Furthermore, the colour transition (blue to red) was also caused by heating the polymerized Langmuir-Blodgett (LB) films at about 60°C. The colour transition of the polymerized PDA Langmuir film exhibited reversibility at the air-water interface when the condition of the subphase was changed, but that of the LB films did not exhibit reversibility. In the differential scanning calorimetry diagrams, the PDA LB films had an endothermal peak a 67°C, but the polymerized film had two peaks at about 70 and 200°C. These results indicate that the photoreactivity of the PDA monomolecular film at the air-water interface was affected by the molecular arrangement and density, and the colour transition of the PDA polymer may be caused by the structural disorder of the side-groups joined to the polymer backbone.

Preparation and properties of polymer Langmuir-Blodgett films with cyclobutane rings

A novel photoresponse LB film was prepared using polymers or oligomers which have cyclobutane rings. The polymers and oligomers with long-chain alkyl ester residues attached to cyclobutane rings formed stable monolayers on the water surface when mixed with arachidic acid. These monolayers could be transferred successfully onto a substrate, forming Y-type films. The oligomer film was polymerized by visible light irradiation. The polymer film showed a photo-reversible process between polymers and oligomers, depending on the wavelength of the irradiating light. This phenomenon was found to be caused by the cleavage and formation of cyclobutane rings in the main chain.

Syntheses of conducting polymer Langmuir-Blodgett multilayers

Three types of method for the preparation of conducting polymer Langmuir-Blodgett (LB) films with high conductive anisotropy are demonstrated. The resulting LB multilayers of polypyrrole derivatives and a polyaniline derivative exhibit anisotropic conductivity due to the alternating layered structure ofsb conducting polymer layers and insulating alkyl or perfluoroalkyl chain layers.

Determination of the whole set of elastic constants of a polymeric Langmuir-Blodgett film by Brillouin spectroscopy.

We report Brillouin light scattering experiments on polymeric uniaxial Langmuir-Blodgett films, which have their preferred axis, the c axis, in the plane of the film. Both acoustic surface and bulk modes were observed. In addition to the usual Rayleigh and Sezawa film modes, a longitudinal guided acoustic phonon was identified. Also observed, and verified by computer simulations, was a resonant enhancement of the scattering cross section for some Sezawa modes due to an additional bulk coupling mechanism of the scattered light to the film modes. The complete set of elastic constants as well as the refractive indices were determined from the spectra. For the samples that we had measured, with more than ten molecular monolayers, the elastic constants do not depend on the film thickness. The ratio between the transverse and the longitudinal sound velocities is found to be much smaller than for ordinary solids.

Spreading behaviors of polymers having aromatic chromophores in a barium stearate monolayer and preparation of the polymer Langmuir-Blodgett films

Incorporation de polyvinylcarbazole, polyvinylnaphtalene et polystyrene dans une couche LB sous forme d'une couche monomoleculaire avec un acide gras, dispersion du polymere dans la couche monomoleculaire