Langmuir-Blodgett Films Of Poly Research Articles

Langmuir and Langmuir-Blodgett Films of Poly[(9,9-dioctylfluorene)-co-(3-hexylthiophene)] for Immobilization of Phytase: Possible Application as a Phytic Acid Sensor.

In this work, the copolymer poly[(9,9-dioctylfluorene)-co-(3-hexylthiophene)] was employed as a matrix for immobilizing phytase, aiming at the detection of phytic acid. The copolymer was spread on the air-water interface forming Langmuir monolayers and phytase adsorbed from the aqueous subphase. The interactions between the copolymer and the enzyme components were investigated with surface pressure and surface potential-area isotherms, Brewster angle microscopy, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The enzyme could be incorporated in the monolayers from the aqueous subphase, expanding the copolymer films and maintaining its secondary structure. The polymeric films presented a morphological heterogeneous pattern at the air-water interface because of the ability of their chains to fold and entangle, causing inherent defects in the organization as well as unbalanced lateral distribution at the air-water interface because of the formation of aggregates. The interfacial films were transferred to solid supports as Langmuir-Blodgett films and characterized by PM-IRRAS and scanning electronic microscopy, which showed not only the co-transfer of the enzyme but also the maintenance of their heterogeneous morphological pattern. The enzymatic activity of the blended film was analyzed by UV-vis spectroscopy and allowed the estimation of the value of the Michaelis constant (13.08 mM), demonstrating the feasibility of the system to selectively detect phytic acid for biosensing purposes.

Electrocatalytic (Bio)Nanostructures Based on Polymer-Grafted Platinum Nanoparticles for Analytical Purpose.

Functionalized platinum nanoparticles (PtNPs) possess electrocatalytic properties toward H2O2 oxidation, which are of great interest for the construction of electrochemical oxidoreductase-based sensors. In this context, we have shown that polymer-grafted PtNPs could efficiently be used as building bricks for electroactive structures. In the present work, we prepared different 2D-nanostructures based on these elementary bricks, followed by the subsequent grafting of enzymes. The aim was to provide well-defined architectures to establish a correlation between their electrocatalytic properties and the arrangement of building bricks. Two different nanostructures have been elaborated via the smart combination of surface initiated-atom transfer radical polymerization (SI-ATRP), functionalized PtNPs (Br-PtNPs) and Langmuir-Blodgett (LB) technique. The first nanostructure (A) has been elaborated from LB films of poly(methacrylic acid)-grafted PtNPs (PMAA-PtNPs). The second nanostructure (B) consisted in the elaboration of polymer brushes (PMAA brushes) from Br-PtNPs LB films. In both systems, grafting of the glucose oxidase (GOx) has been performed directly to nanostructures, via peptide bonding. Structural features of nanostructures have been carefully characterized (compression isotherms, neutron reflectivity, and profilometry) and correlated to their electrocatalytic properties toward H2O2 oxidation or glucose sensing.

Nanostructured LB films developed from poly(p-acryloylaminophenylmethylphosphonic) acid

ABSTRACTIn this paper, the formation of Langmuir-Blodgett films of poly(p-acryloylaminophenylmethylphosphonic) acid polymers, with general formula (C10H12NPO4)n are reported. The Langmuir-Blodgett (LB) technique was used for building ordered nanostructures in molecular assemblies of these polymers, which were able to form stable films. At the air-water interface, these polymers (with low and high molecular weight) formed Langmuir (L) monolayers, which were characterized by surface pressure versus molecular area (π-A) isotherms and Brewster´s Angle Microscopy (BAM). Using the LB method, molecular mono and multilayer films of these polymers were prepared and transferred onto glass substrates forming Z-type multilayers, with a transfer ratio close to unity. These LB films were characterized by Atomic Force Microscopy (AFM).

강유전 고분자 박막의 저차원 전기광학 특성

Department of Laser and Optical Information Technology, Cheongju University, Cheongju 360-764, Korea(Received February 14, 2014; Revised February 23, 2014; Accepted February 25, 2014)Abstract: The electro-optic properties in Langmuir Blodgett films of poly (vinylidene fluoride trifluoroethylene) are investigated in the crossover region between two and three dimensions. The absence of finite size effect is observed in the films thinner than 20 nm, which confirms that these films are two dimensional ferroelectrics. The copolymer LB film of P(VDF-TrFE) exhibits the largest electro-optic response(26 pm/V) at 10 layer thickness. The cross-over behavior of electro-optic effect around the 10 layer thickness was discussed with the formation of nanomesa after thermal annealing. Keywords: Langmuir-Blodgett, P(VDF-TrFE), Ferroelectric, Electro-optic, Finite size effect

Chemical imaging of self-assembling structures in Langmuir–Blodgett films of polymer blends

The ability of tailoring surface properties is crucial in a large number of applications, so that a wide range of surface engineering techniques has been developed in the last decades. Among these techniques, those based on the surface functionalization by means of self-assembled monolayers and Langmuir–Blodgett (LB) films are peculiarly attractive because of, simplicity, versatility. In particular, this work concerns the functionalization of insulating surface with macromolecular systems disguised as LB films. In particular, we will show that patterned LB films of poly(2-vinylpyridine) (P2VP) and polystyrene (PS) blends can be obtained by careful control of the ratio of polymer components in the blend. Surface separation phase phenomena, crucial to the patterning purposes, can be evidenced by ToF-SIMS chemical imaging. Furthermore, the film morphology can be thoroughly examined by means of scanning probe microscopies (SPM) techniques. It will be shown that three main types of structures can be obtained by changing the ratio between two polymers. In particular, by increasing the relative amount of PS, structures with different shapes can be fabricated. Round-shaped structures have been obtained by using low relative quantity of PS, single wires and entangled wires have been obtained by using relative intermediate quantity of PS and high relative quantity of PS, respectively.

Inhibition of corrosion by poly( N-hexadecylaniline)/docosanol mixed Langmuir–Blodgett films on copper in sea water

Electrochemical and weight loss techniques have been used for investigation of inhibition of corrosion on copper metal by Langmuir–Blodgett (LB) films of poly( N-hexadecylaniline)/docosanol in sea water. LB films of poly( N-hexadecylaniline)/docosanol were deposited onto the copper specimens. The open-circuit potential and potentiodynamic polarization curves were observed to shift in noble direction, which indicated that these LB films could inhibit the corrosion of copper metal in sea water.

Pyroelectric study of polarization switching in Langmuir-Blodgett films of poly(vinylidene fluoride trifluoroethylene)

The ferroelectric switching in Langmuir-Blodgett films of poly(vinylidene fluoride trifluoroethylene) is studied. The films have a distribution of switching times several decades wide. Nearly a half of the film volume may be switched faster than 1ms, though complete switching of a whole sample may require 100s or more. The switching occurs through a domain nucleation and growth mechanism. The decay of polarization at zero bias is logarithmic in time, with a constant rate below 5% per decade at room temperatures. The coercive voltage may be as low as 5V, which makes the films promising for use in nonvolatile random-access data storage.

Quartz crystal microbalance and electrochemical studies on the electrode modified by layer-by-layer multilayers of viologen polyelectrolytes

Cationic poly(viologen) derivatives [(V 2+) m ] and anionic polymer [poly(styrenesulfonic acid- co-maleic acid), sodium salt] were assembled on electrode surfaces by layer-by-layer (LBL) and Langmuir–Blodgett (LB) methods. The assembling process was in situ investigated by quartz crystal microbalance (QCM) technique. Based on the frequency change, the average surface coverage of poly(butylviologen) in the LBL multilayers is in the range of 1.6∼3.3×10 −10 mol/cm 2. The mass change for one-layer LB film of poly(dodecylviologen)-anionic polymer is about 44, 96 and 263 ng/cm 2 for the films deposited at 5, 10 and 15 mN/m, respectively. The assembled LBL and LB multilayers show well reversible redox characteristics of the viologen. For poly(viologen) with short alkyl chains, the cyclic voltammograms (CVs) show two redox couples of (V 2+) m ↔ (V +) m and (V +) m ↔ (0.5(V +) 2) m when the last layer is poly(viologen), or one redox couple of (V 2+) m ↔ (V +) m when the last layer is anionic polymer. While for poly(viologen) with long alkyl chains, the CVs show only one couple of (V 2+) m ↔ (V +) m . The LBL multilayers show much higher stability than the self-assembled monolayers and LB films in electrolyte solution.

Infrared studies of mixed Langmuir–Blodgett monolayers of octadecyldimethylamine oxide and dioctadecyldimethylammonium chloride with arachidic acid and poly(acrylic acid)

Infrared reflection–absorption spectra (IRAS) have been measured for monolayers of octadecyldimethylamine oxide (C 18DAO), dioctadecyldimethylammonium chloride (2C 18DAC) and their mixtures with arachidic acid and poly(acrylic acid) prepared by Langmuir–Blodgett (LB) technique on gold-evaporated glass slides. The spectra show that arachidic acid and C 18DAO or 2C 18DAC molecules form well-ordered monolayers with trans zigzag conformations. The order of the alkyl chain in C 18DAO is greatly increased upon the formation of the mixed LB film. The relative intensities of infrared bands due to CH 2 and CH 3 stretching modes of the hydrocarbon chains indicate that they are tilted with respect to the surface normal in the mixed LB films of arachidic acid and C 18DAO or 2C 18DAC. The hydrocarbon chains of C 18DAO and 2C 18DAC are disordered in the mixed LB films of poly(acrylic acid) and C 18DAO or 2C 18DAC.

Charge Carrier Mobility in Langmuir-Blodgett Films of Poly(3-hexylthiophene)

Abstract The tendency to saturation in the collected charge as a function of light intensity in Langmuir-Blodgett films of poly(3-hexylthiophene) (PHT) has been studied. The tendency to saturation can have two reasons; that the space charge limited current regime has been reached, or influence of very fast bimolecular recombination. We have studied these two cases, and we conclude that bimolecular recombination is a probable cause for the tendency to saturation. The hole mobility in PHT can therefore possibly be estimated as high as 1 cm2/Vs in the initial stage after photoexcitation.

Langmuir and Langmuir-Blodgett Films of Poly(vinylpyridine)s Quaternized with Long-Chain Alkyl Halides

Poly(N-alkyl-4-vinylpyridinium halide)s was prepared by reacting two poly(4-vinylpyridine)s (M v 25000 and 42700° with a range of straight-chain alkyl halides. The percentage of pyridine moieties quaternized was ca. 50% or ≥ 91%. Monolayers of the various products on water displayed good isotherms which included significant «solid» regions and collapse pressures ≥ 26 mN/m. The monolayers could be transferred onto hydrophobic Si wafers. The monolayers of polymers with side chains containing ≤ C 11 transferred well on the upstroke and not at all ot only partially on the downstroke, though low angle X-ray diffraction data indicated that the multilayers produced Y-type structures

Monolayers and Langmuir-Blodgett Films of Poly(N-acylethylenimines) with Hydrocarbon and Fluorocarbon Side Chains

A series of poly(N-acylethylenimines) with hydrocarbon and fluorocarbon side chains varying in length from 6 to 17 carbon atoms were prepared by cationic ring-opening polymerization of 2-oxazolines. The behavior of monolayers of these materials at the air-water interface was studied in a Langmuir through, and multilayer Langmuir Blodgett (LB) films were prepared. Both monolayer behavior and LB film formation were strongly dependent on the size and nature of the side chains. Polymers with short hydrocarbon side chains (6-11 carbon atoms) form fluid liquil like condensed monolayers in which the polymer backbone is at the water surface and the side chains are tilted toward the air. They can be easily transferred onto solid substrates, and uniform LB films can be prepared

Influence of γ-radiation on the properties of Langmuir-Blodgett films of poly (3-hexadecylthiophene) in interaction with selected environment-polluting gases

The influence of γ-radiation on the electric properties of Langmuir-Blodgett (LB) films of partially iodine-doped poly-(3-hexadecylthiophene) and stearic acid in interaction with selected environment-polluting gases has been studied. CO2, CO and NO2 increase the LB films conductivity and NO has a tendency to decrease the electric conductivity. The influence of γ-radiation was expressive onyl in the case of CO2, whereas NO2 brought about degradation of the conductive polymer.

Photoluminescence quenching in a polymer thin film field effect luministor

The interaction between photoexcited excitons and field induced charges in poly(3-hexylthiophene) has been studied using photoluminescence. Thin films of poly(3-hexylthiophene) and Langmuir-Blodgett films of poly(3-hexylthiophene)/Arachidic acid show a quenching of the photoluminescence intensity upon charge injection in a field effect device. The quenching is discussed in terms of polarons/bipolarons acting as recombination centra for the excitons, giving non-radiative decay. The rate constant for non-radiative recombination of the excitons is shown to be proportional to the number of injected charges. This field effect luministor device shows the coupling between the optical and electronic properties of excitations in conjugated polymers.

Preparation and Characterization of langmuir-Blodgett Films of Poly(p-(methyl)phenylmethacrylates)

Abstract The behavior of poly(p-(methyl)phenyl methacrylate) monolayer at the air-water interface was investigated. The surface pressure-area isotherms are dependent on a series of parameters such as molecular weight, temperature and compression-expansion cycle. The multilayer LB films are X- or Z-types and their packing and conformation are characterized by UV, FTIR and ellipsometry.

Resonance raman scattering from spincoated and langmuirblodgett poly(3-alkylthiophene) films

Spincoated poly(3-hexylthiophene) and Langmuir-Blodgett films of poly(3-hexylthiophene)/ arachidic acid with a different number of layers have been studied by resonance Raman scattering. In both kinds of samples a clear dispersion was observed for the Raman line of the amplitude mode. This dispersion effect is much higher for spincoated films as compared to LB films. We interpret this behaviour by the conjugation length model using the A-term of the Albrecht theory. An average conjugation lenght of about four thiophene rings was found for spincoated samples and a higher value for the LB films.

Effect of structure on the properties of polyconjugated systems

The modification of chemical structure may modulate the properties of polyconjugated system in order to optimize the applications in different fields. Many properties can be tuned ranging from the solubility to the band gap of the polymer. Moreover, the presence of a polar group in the side chain open new possibilities in the preparation of ordered molecular architecture such as Langmuir Blodgett films. We will discuss these parameters focusing our attention mainly on the preparation of Langmuir Blodgett films of poly(3-alkylthiophene) and of low band gap structure.

Monolayers and Langmuir-Blodgett films of poly(N-acylethylenimines)

Monolayers and Langmuir-Blodgett films of poly(N-acylethylenimines)

Langmuir-Blodgett films of poly(isocyanide)s with different sidechains. 2. poly(3-cholesteryl-6-isocyanohexanoate)

A poly(isocyanide), [RNC <] n , with pendant cholesterol side groups forms stable Langmuir-Blodgett (LB) monolayers at the air-water interface. At high surface pressures, the monolayers are spontaneously transformed into bilayer structures. The monolayer was transferred onto various solid substrates to form LB multilayers. FT-IR, ellipsometry and SAXS indicate that in these multilayers the polymer side chains are oriented perpendicular to the substrate surface.

Surface acoustic wave vapor sensors based on resonator devices

Abstract : Surface acoustic wave (SAW) devices fabricated in the resonator configuration have been used as organic vapor sensors and compared with delay line devices more commonly used. The experimentally determined mass sensitivities of 200, 300, and 400 MHz resonators and 158 MHz delay lines coated with Langmuir-Blodgett films of poly(vinyl tetradecanal) are in excellent agreement with theoretical predictions. The response of LB- and spray-coated sensors to various organic vapors were determined, and scaling laws for mass sensitivities, vapor sensitivities, and detection limits are discussed. The 200 MHz resonators provide the lowest noise levels and detection limits of all the devices examined.