Preparation of carboxylate groups-containing thin films by plasma polymerization

Summary Plasma polymerization in a mixture of acrylic acid and carbon dioxide (CO₂) gas was investigated. The polymer deposition rate in plasma polymerization of acrylic acid increased by admixing CO₂ gas, and polymers containing carboxyl groups were formed. The amount of carboxyl groups alterable to carboxylate anions by treating with 0.1 N KOH solution or NH₃ gas reached twice of that formed in plasma polymerization without CO₂ gas.     

Analysis of annealed thin polymer films prepared from dichloro(methyl)phenylsilane by plasma polymerization

Thin plasma polymer films were deposited from a mixture of dichloro(methyl)phenylsilane (DCMPS) vapor and gaseous hydrogen in an rf (13.56 MHz) capacitive coupling deposition system on pieces of silicon wafers. Some of samples were annealed in a vacuum to temperatures ranging from 450 to 700°C. The chemical composition, structure, and surface morphology of the annealed samples and those stored in air at room temperature were studied by FTIR, XPS, SEM, and optical microscopy. The thermal stability and decomposition of the plasma polymer with increasing temperature were characterized using thermogravimetry together with mass spectrometry. The plasma polymer was stable to a temperature of 300°C. Above that temperature, the material started to decompose together with additional crosslinking due to the incorporation of extra oxygen atoms forming new siloxane bonds. The plasma polymer was tough at room temperature but much more brittle after annealing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2106–2112, 2001     

Diamond-like carbon thin films prepared by ECR argon plasma assisted pulsed laser deposition

Diamond-like carbon films were prepared by pulsed laser ablation of graphite target in argon plasma produced from electron cyclotron resonance (ECR) microwave discharge and analyzed by Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The analysis shows that the films prepared with argon plasma assistance have different chemical structure compared with the films prepared in vacuum without plasma assistance. The structure of the films prepared with plasma assistance depends strongly on the bias voltages applied on the substrate. Surface morphology observation shows that the films prepared with argon plasma assistance have a smoother surface than the films prepared without plasma assistance. The re-sputtering of the growing film due to the bombardment of the plasma stream results in reduction of the deposition rate. The ablation plumes during film preparation with and without plasma assistance were examined through optical emission spectroscopy. In vacuum, emission lines from mono-atomic carbons and carbon ions dominate the plume emission. In argon plasma, the plume emission exhibits different behavior in its temporal and spatial evolution. It is initially dominated by strong lines from mono-atomic carbons and carbon ions and then evolves to consist mainly of emissions from C₂ molecules superposed on a featureless continuum. It is also found that the emission intensity of the C₂ molecules as well as the continuum varies with the bias voltages.     

Thin polypyrrole films prepared by chemical oxidative polymerization

Polypyrrole (PPY) films with a thickness of 3–4 μm were obtained by chemical oxidation of pyrrole (PY) at the interface of chloroform and water with an oxidant (NH₄)₂S₂O₈. The films were compact and could be removed with a solid plate. The quality and compositions of these films varied with the molar ratios of the monomer and oxidant of the reaction systems. Overoxidation of polypyrrole was observed and confirmed by the characterizations via infrared spectra and elemental analysis of the films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2169–2172, 1998     

Mn-doped titania thin films prepared by spin coating

TiO₂ thin films doped with ≤7 mol% Mn (metal basis) were deposited on F-doped SnO₂-coated (FTO) glass substrates by spin coating. The structural, morphological, and optical properties of the films were investigated by glancing angle X-ray diffraction (GAXRD), laser Raman microspectroscopy, field emission scanning electron microscopy (FESEM), and ultraviolet–visible spectroscopy (UV–VIS). Mn doping of TiO₂ (anatase) extended the optical absorption edge to longer wavelengths (lower photon energies) significantly lowering the band gap from 3.32 eV (undoped) to 2.90 (7 mol% Mn). The absorption edges of all films were sharp and the transparencies in the visible region were in the range 60–75%. All of the films were homogeneous, fully dense, and essentially crack-free.     

Layered poly(naphthalene) films prepared by electrochemical polymerization

Summary Poly(naphthalene) (PN) has been deposited on a platinum electrode by direct oxidation of naphthalene in BF₃-ethyl ether solution containing 5×10^-3 mol/l water. Experimental results demonstrated that the PN films obtained from the described medium composed many parallel arranged polymer layers. The structures, conductivities and heat resistant properties of the PN products were also studied.     

Preparation of thin films containing sulfonic acid and carboxylic acid groups by plasma polymerization of perfluorobenzene/sulfur dioxide and perfluorobenzene/carbon dioxide mixtures

Summary Plasma polymerizations of the mixture of perfluorobenzene (PFB) and sulfur dioxide (SO₂) or carbon dioxide (CO₂), and the mixture of benzene (BZ) and SO₂ or CO₂ were investigated to obtain plasma polymer films with ionic groups such as sulfonic or carboxylic acid groups. The plasma polymerization of the mixture of PFB or BZ and SO₂ gave plasma polymer films containing sulfonic acid groups. The plasma polymerization of the mixture of PFB and CO₂ deposited plasma polymer films with carboxylic acid groups but that of the BZ/CO₂ mixture deposited plasma films with no carboxylic acid groups.     

Crystallisation kinetics of hydroxyapatite thin films prepared by sol-gel process

Abstract

Abstract

In this study, the crystallisation of nano hydroxyapatite (HA) films on stainless steel 316L was studied. The film was prepared by sol-gel technique. The process was started with preparation of an HA sol. After aging of the sol at room temperature, a stainless steel 316L substrate was dip coated and then was heat treated from 350 to 450°C at different periods of time in air. The crystallisation behaviour and the transformation-temperature-time diagram of HA films were achieved and analysed using the avrami equation. The results showed that the crystallisation of HA began at 250°C and was increased up to 450°C. The obtained HA film showed a nanostructure character with a suitable crystalinity after heat treatment.     

Characterization of CuInS2 thin films prepared by one-step electrodeposition

CuInS₂ thin films were fabricated by one-step electrochemical deposition from a single alkaline aqueous solution and using conductive glass as the substrate. The electrolyte consisted in 0.01 mol L^?1 CuCl₂, 0.01 mol L^?1 InCl₃, 0.5 mol L^?1 Na₂SO₃ and 0.2 mol L^?1 Na₃C₃H₅O(COO)₃ (CitNa) at pH 8. The films were analyzed using a variety of techniques such as X-ray diffractometry, micro-Raman spectroscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy and photoelectrochemistry. After carrying out a thermal treatment in sulfur vapor, chalcopyrite CuInS₂ thin films were obtained. Etching the films in KCN solution was found to be a key step, enabling a final adjustment in the stoichiometry. These thin films exhibited p-type semiconductor behavior with the bandgap of 1.43 eV. The results show that electrodeposition provides a cost-effective and versatile method for the preparation of thin films of CuInS₂, even when acidic precursors need to be avoided.     

Synthesis and characterization of novel biodegradable and biocompatible poly(ester-urethane) thin films prepared by homogeneous solution polymerization

Novel biodegradable and biocompatible poly(ester-urethane)s were synthesized by in situ homogeneous solution polymerization of poly(?-caprolactone) diol, dimethylolpropionic acid (DMPA), and methylene diphenyl diisocyanate in acetone followed by solvent exchange with water. The effects of the DMPA content and hard segment content on the properties of the polyurethanes were measured by DSC, TGA, and hydrolytic degradation measurements. The results showed that DMPA had a dramatic effect on the particle size; the particle size decreased rapidly with increasing DMPA content. The hydrolytic degradation test showed that the degradation rate was little affected by the DMPA content in the range investigated, but was observed to be influenced by the hard segment content. Cell toxicity analysis showed that the biodegradable poly(ester-urethane)s synthesized in this study did not exhibit any detectable toxicity to human umbilical vein endothelial cells and mouse embryonic stem cells. Both types of cells can effectively adhere to and spread on the surface of pure poly(?-caprolactone) or poly(ester-urethane)s. The present study demonstrates the feasibility of a facile synthesis of biodegradable polyurethanes and of their aqueous dispersions with prescribed properties for biomedical applications.     

Barium strontium titanate nanocrystalline thin films prepared by soft chemical method

Barium strontium titanate (Ba_0.65Sr_0.35TiO₃) nanocrystalline thin films, which were produced by the soft chemical method, were crystallized at low temperature using a domestic microwave oven. A SiC susceptor were used to absorb the microwave energy and rapidly transfer the heat to the film. Low microwave power and short time have been used. The films obtained are crack-free, well-adhered, and fully crystallized. The microstructure displayed a polycrystalline nature with nanograin size. The metal-BST-metal structure of the thin films treated at 700 °C show good electric properties. The ferroelectric nature of the BST35 thin film was indicated by butterfly-shaped C–V curves. The capacitance–frequency curves reveal that the dielectric constant may reach a value up to 800 at 100 kHz. The dissipation factor was 0.01 at 100 kHz. The charge storage density as function of applied voltage graph showed that the charge storage densities are suitable for use in trench type 64 Mb (1–5 μC/cm²) and 265 Mb (2–11 μC/cm²) DRAMs.     

XPS spectra of thin CNx films prepared by chemical vapor deposition

Carbon nitride (CN_x) thin films with an N/C ratio of 0.605:0.522 have been synthesized using different sources as a ksilol, CCl₄, N₂ and NH₃ by PECVD (plasma enhanced chemical vapor deposition) and hot filament-CVD reactors. X-ray photoelectron spectroscopy (XPS) analyses, which give C_1s peaks with a maximum at 285.7 eV and 287 eV, typical for C–N bonds and sp² hybridization and CN bonds and sp³ hybridization, respectively. The observed and N_1s peaks with a maximum at about 399 eV suggest the existence of different C–N bonds and polycrystallite structure in the amorphous carbide matrix. The concentration of the different CN bonds varies, depending on the deposition technique.     

Properties of amine‐containing coatings prepared by plasma polymerization

Two monomers, ethylenediamine (EDA) and diaminocyclohexane (DACH), were plasma‐polymerized in continuous‐wave (CW) and pulse modes. The influence of different plasma parameters on the deposition rate and film composition were investigated in detail and the changes in aminofunctionalization with varying pulse parameters were examined by FTIR, ESCA, and chemical‐derivatization techniques. It was shown that a varying duty cycle does not produce a considerable effect on the retention of amine groups into the film, while power and t_on play a significant role in the polymerization process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 979–990, 2004     

Pervaporation of ethanol-water mixture by plasma films prepared from hexamethyldisiloxane

The plasma polymerization process was investigated to obtain plasma films like poly(dimethylsiloxane), and the formed films were applied as membranes for pervaporation of ethanol-water solution.

A reaction chamber which had the triode electrode structure for initiation of a glow discharge was provided for preparation of films like poly(dimethylsiloxane) by plasma polymerization. Films plasma-polymerized from hexamethyldisiloxane (HMDSO) resembled poly(dimethylsiloxane) in spectroscopic view and were composed of dimethylsiloxane chains with branches of trimethylsilyl groups. The surface energy for the films was 19.6 mN/m. The films deposited from HMDSO on Nuclepore membrane showed good ethanol-selectivity in pervaporation of ethanol-water solution. The separation factor depended on the film thickness as well as the feed composition. The film-thickness effect was maximized at 34 nm thick, and the separation factor reached 4.5. A model for the separation process using our composite membrane was discussed.     

Ethylene and propylene polymerization catalyzed by a model Ziegler-Natta catalyst prepared by gas phase deposition of magnesium chloride and titanium chloride thin films

Model Ziegler-Natta catalysts are prepared by gas phase deposition of ultra-thin TiCl₄/ MgCl₂ films in UHV conditions. A monolayer of TiCl₄ chemisorbed on a solid solution of titanium and magnesium chloride is formed in this way. The reduction and alkylation of TiCl₄ by its reaction with a liquid layer of AlEt₃ condensed on the halide film is monitored by XPS. Most of the TiCl₄ is reduced by AlEt₃ and is incorporated in the mixed titanium /magnesium chloride. The model catalyst is active in the polymerization of ethylene and propylene at 300 K, both in the absence and in the presence of AlEt₃ in the reaction cell. The polymers that form over the catalyst film have been characterized by Raman spectroscopy. The weak signals from methyl end groups and unsaturations suggest high molecular weight for both polymers. The polypropylene film has a high degree of isotacticity even without the use of any electron donor. For the propylene polymerization reaction the overall turnover frequency is in the range between 0.1 and 1 molecule/(site s).     

Immobilization of urease on cation-exchange membranes prepared by radiation-initiated graft copolymerization of acrylic acid on polyethene thin films

Summary A covalent immobilization of urease was conducted on carboxylic cation-exchange membranes (CEM) prepared by radiation-initiated graft copolymerization of acrylic acid (AA) on polyethene (PE) thin films. Six types of CEM with different grafting degree (from 26.5 to 95.2%) were used as carry. The carboxyl groups were activated by the carbodiimide method in order to carry out a covalently immobilization. The amount of bound protein and the enzyme activity were determined in each immobilized system. It was established that the urease, immobilized on CEM with 64.2% grafting degree, featured the highest relative activity – 80.32%. The amount of bound protein on this membrane type was 6.01 mg/cm². The basic characteristics of the immobilized and the free enzymes were determined (pH_opt, T_opt and pH_stab). It was found out that the immobilized urease had greater thermal and storage stability in comparison with the free enzyme. It was proven that CEM with a grafting degree of 64.2% would be a suitable carrier for urease immobilization.     

Structural and mechanical properties of CNx thin films prepared by magnetron sputtering

In an attempt to define the role of nitrogen in CN chemical bonding and in the formation of CN_x thin films, several coatings with a variable concentration of N₂ were grown onto (100) Si substrates using magnetron sputtering in N₂/Ar discharge. The chemical composition of the as-deposited films was investigated by means of Rutherford backscattering spectroscopy (RBS) and showed an [N]/[C] ratio up to 0.7. Raman and Fourier transform infrared (FTIR) spectroscopy were carried out to measure the optical vibration properties for studying the bonding state of nitrogen.By means of grazing incidence X-ray diffraction (XRD) and transmission electron microscopy (TEM) electron diffraction the structure of the deposited films was proven to be mainly amorphous containing small crystallites of CN_x compounds. Scanning tunneling microscopy (STM) shows the clusterlike surface of the films where the cluster size is characterized by scaling behaviour. The mechanical properties of the CN_x thin films adhering their substrates were investigated using the nanoindentation technique. From the load–displacement curve the hardness H and the Young's modulus E of the films were calculated.The relationships between deposition parameters and properties of CN_x films are shown and discussed. In particular, the influence of the applied r.f. power and the role of the N₂ partial pressure are demonstrated.     

Porous acrylonitrile/itaconic acid copolymers prepared by suspended emulsion polymerization

Porous acrylonitrile (AN)/itaconic acid (IA) copolymers were successfully prepared by suspended emulsion polymerization for the first time, with potassium peroxydisulfate (KPS) as an initiator, poly(vinyl alcohol) (PVA) as a dispersant agent, and Span80 as an emulsifier. The effects of the water/monomer mass ratio, agitation conditions, KPS concentration, PVA concentration, Span80 concentration,s and IA concentration on the average particle size and size distribution, particle morphology, and porosity of the AN/IA copolymers were investigated. The results show that the final AN/IA copolymers formed with agglomerates of primary particles had a porous structure, low particle density, and uniform particle size and did not agglomerate easily between the particles. The preparation conditions for the AN/IA copolymers were optimized as follows: (1) the water/monomer mass ratio was 0.3 : 1; (2) the concentrations of KPS, IA, PVA, and Span80 were 0.5, 12.4, 0.1, and 0.5 wt %, respectively, based on the weight of AN separately; (3) the agitation rate was 400 rpm; (4) the polymerization temperature was 70°C; and (5) the reaction time was 3 h. The size of the final AN/IA copolymer particles was in the range 200–400 μm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of annealing on SiC thin films prepared by pulsed laser deposition

Crystalline cubic SiC thin films were successfully fabricated on Si(100) substrates by using laser deposition combined with a vacuum annealing process. The effect of annealing conditions on the structure of the thin films was investigated by X-ray diffraction and Fourier transform infrared spectroscopy. It was demonstrated that amorphous SiC films deposited at 800°C could be transformed into crystalline phase after being annealed in a vacuum and that the annealing temperature played an important role in this transformation, with an optimum annealing temperature of 980°C. Results of X-ray photoelectron spectroscopy revealed the approximate stoichiometry of the SiC films. The characteristic microstructure displayed in a scanning electron microscope image of the films was indicative of epitaxial growth along the (100) plane.