Synthesis by plasma and characterization of bilayer aniline–pyrrole thin films doped with iodine

The synthesis by plasma and characterization of aniline–pyrrole bilayer polymers doped in situ with iodine were studied. The objective was to study the electrical conductivity of thin films composed of alternating layers of different polymers. The results indicated that the plasma technique is capable of forming chemically bonded layered polymers with several possible combinations. The electric conductivity was studied during heating–cooling cycles so the dependence of the bilayer polymers on temperature could be observed. The behavior was related with the Arrhenius model, with average activation energies of 0.4 ± 0.1 eV in the heating steps and 0.5 ± 0.1 eV in the cooling steps. The difference in both steps shows the influence of the aniline in the bilayer polymer network because polyaniline presents changes in the structure during heating processes. The bilayer aniline–pyrrole polymers had greater electric conductivity at room temperature than that shown by the separate homopolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1850–1856, 2002     

Diffusion,evaporation, and surface enrichment of a plasticizing additive in an annealed polymer thin film

We present the first measurements of the simultaneous diffusion, surface enhancement, and evaporation of a plasticizer from a polymer, thin-film matrix using neutron reflection techniques. The reflectivity profiles as a function of the annealing time at an elevated temperature yield the time-dependent, plasticizer volume fraction profiles in a polyester–polyurethane (Estane) film. Thin, plasticizer-enriched layers form at both the polymer/substrate and polymer/air interfaces for annealed and unannealed samples. The diffusion equations for a material diffusing through a film and then evaporating into a vacuum at the free surface describe the loss of the plasticizer from the film for annealed samples. The loss of the plasticizer from the film is not limited by the movement of the plasticizer through the polymer matrix but is dominated by the plasticizer's rate of evaporation from the surface. The rate of evaporation and the volume fraction profiles for the plasticizer at the substrate interface are both consistent with surface attractions dominating over bulk attractions between the miscible plasticizer and the polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3258–3266, 2004     

Crystallinity of poly(3‐hexylthiophene) in thin films determined by fast scanning calorimetry

Using fast scanning calorimetry, we determined the crystallinity of thin films of poly(3‐hexylthiophene) crystallized from the melt from measurements of the specific melting enthalpy. A broad range of film thicknesses from 10 µm down to 26 nm was covered. The sample mass was determined from measurements of the specific heat capacity in the molten state allowing a quantitative analysis of the heat flow data. Films with a thickness 400 nm slowly cooled from the melt showed the same crystallinity as bulk samples measured with conventional DSC. Below 350 nm the melting enthalpy decreased strongly. We assign this strongly reduced crystallinity to the restricted crystallization kinetics originating from hindered spherulitic growth under thin film confinement. A higher crystallinity could be partially regained by extended isothermal crystallization at elevated temperatures. Much faster cooling, with rates above about 100 Ks^?1 led to a partial suppression of crystallization even for thick films. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1791–1801     

Layered self-organized structures on poly(3-octylthiophene) thin films studied by scanning probe microscopy

The morphology and mechanical properties of poly-(3-octylthiophene) P3OT films thin has been studied by scanning force microscopy techniques. On these films we find self-assembled layered structures that appear regardless of the preparation conditions, that is, spin-coating or drop-casting, of the solvent concentration or of the type of substrate. Using the drop-casting method for sample preparation these layered structures are hardly visible due to the high surface roughness, while using spin-coating these structures are the main topographic feature on the surface. These structures have typically one or two layers, even though occasionally up to four layers have been observed. Each layer has a height of 4-5 nm, which is associated to crystalline P3OT domains and lay on the polymer film. The size of these structures increases with increasing concentration of the P3OT in the solvent. We find well differentiated morphological, electrostatic as well as mechanical properties for the self-assembled structures as compared to the rest of the polymer film. Finally, the growth rate of these structures has been studied.     

Analysis of blends of poly(styrene‐co‐acrylonitrile) with an epoxy/aromatic amine resin using scanning thermal microscopy

Using a microthermal analyzer TA Instruments 2990 μTA, we have analyzed the morphologies developed for the resin tetraglycidyl‐4,4′‐diaminodiphenylmethane cured with an aromatic amine 4,4′‐diaminodiphenylsulphone modified with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic. The phase‐separation phenomenon induced by polymerization was also followed by scanning electron microscopy. Using the modulated local thermal‐analysis mode of μTA, the glass‐transition temperatures of different domains for each sample were evaluated. Dynamic mechanical analyzer experiments were made to evaluate the macroscopic thermal properties of the blends. A morphology was well established for all blends examined with these techniques showing a nodular structure, the epoxy‐rich phase, and a continuous phase, the SAN‐rich phase, that forms the matrix. From both microscopic and macroscopic thermal analyses, it is concluded that a phase separation exists for the blends investigated. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 284–289, 2002     

Fluorescence staining and confocal laser scanning microscopy study of hydrogen-bonded poly(vinylpyrrolidone)/poly(acrylic acid) film

Poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA) were layer-by-layer (LBL) assembled to prepare the thin films based on hydrogen-bonding complexation. The hydrogen-bonded PVPON/PAA films were incubated in acidic, neutral and basic vapors separately. To study the morphologies after incubation, the films were stained by pH-sensitive fluorescent dyes using chemical and physical ways, and investigated with confocal laser scanning microscope (CLSM). The chemical way (labeling) was covalently linking fluoresceinamine (FAM) to some monomer units of PAA while the physical way was adsorbing rhodamine B (RB) molecules from dilute solution. Atomic force microscope (AFM) was combined with CLSM to find that after incubation in neutral or basic vapor the hydrogen-bonded PVPON/PAA films form porous structure and the pores are through the whole film.     

Mechanism of plasma polymerization ofN-silyl-substituted cyclodisilazane: Structure and properties of polymer film

NN-Bis(dimethylsilyl)tetramethylcyclodisilazane (NSCDSN) was selected for plasma polymerization as a model monomer representing N-silyl-substituted cyclodisilazanes. Owing to the aromatic character resulting from the strong (d-p) coupling between silicon and nitrogen atoms, these compounds manifest the highest thermal stability among the organosilicones. GC/MS examination of a low-molecular-weight fraction evaporated from the plasma polymer revealed the presence of various monomer derivatives having mostly the general structure of N-silyl-substituted cyclodisilazane (Si₄N₂) units. GC/MS and ATR/IR studies have shown that the Si₄N₂ skeleton displays a high resistance to plasma fragmentation and that it was incorporated as such into the polymer film. A radical mechanism for plasma polymerization was postulated assuming the formation of and propagation precursors. The low value found for the polar component of the surface free energy confirmed the contribution of Si₄N₂ units to the polymer film. TGA investigation showed the rate and degree of thermal decomposition of plasma-polymerized (PP) NSCDSN to be lower than those of plasma polymers from N-hydrogen-substituted silazanes. Vacuum pyrolysis, at 800°C, converted the polymer film into a glassy, dense, and almost inorganic material with a strong adhesion to the metal substrates.     

Cellulose-poly(vinyl pyrrolidone) blends studied by scanning electron microscopy and dynamic mechanical measurements

New polymer blends based on cellulose and poly(vinyl pyrrolidone) (PVP) were obtained using a mixture of N=methyl morpholine N-oxide (NMMO) and dimethylsulfoxide (DMSO) as a common solvent system. Materials are obtained after the removing of NMMO-DMSO in three of their different solvents, namely i) H₂O, ii) a mixture 95/5 vol/vol hexamethyl phosphororri amide (HMPA) DMSO and iii) a mixture of 95/5 vol/vol dioxan/water.Scanning electron microscopy techniques were extensively used and lead to the conclusion that all these blends in the composition range 25/75 w/w to 75/25 w/w cellulose/PVP are two-phase systems in which cellulose forms a continuous phase. Preliminary results from calorimetric and dynamic mechanical measurements confirm these observations. Furrthermore, it is shown that using dioxanwater preserves the initial cellulose PVP composition, allowing to get blends with the desired PVP fraction. Although it is not the case with HMPA/DMSO which dissolves a part of PVP, its use leads to assymmetric, porous structures.     

Details of surface features in aromatic polyamide reverse osmosis membranes characterized by scanning electron and atomic force microscopy

In the present article, some new events on the surface morphology of the aromatic polyamide thin‐film‐composite (TFC) membranes were demonstrated in conjunction with their inherent chemical nature. In addition, the detailed, quantitative understanding of the microscopic surface features was shown to be essential in controlling the water permeability and eventually developing the high performance membranes. The surface roughness and the surface area were mainly affected by the existence or nonexistence of the crosslinking and/or the free amide groups not pertinent to the formation of the hydrogen bonding, which in turn contributed to the water permeability. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1429–1440, 1999     

Ion‐beam‐induced morphology on the surface of thin polymer films at low current density and high ion fluence

The effect of Xe⁺ bombardment on the surface morphology of four different polymers, polystyrene (PS), poly(phenylene oxide), polyisobutylene, and polydimethylsiloxane, was investigated in ion energy and fluence ranges of interest for secondary ion mass spectrometry depth‐profiling analysis. Atomic force microscopy (AFM) was applied to analyze the surface topography of pristine and irradiated polymers. AFM analyses of nonirradiated polymer films showed a feature‐free surface with different smoothness. We studied the influence of different Xe⁺ beam parameters, including the incidence angle, ion energy (660–4000 eV), current density (0.5 × 10² to 8.7 × 10² nA/cm²), and ion fluence (4 × 10¹⁴ to 2 × 10¹⁷ ion/cm²). Xe⁺ bombardment of PS with 3–4 keV at a high current density did not induce any change in the surface morphology. Similarly, for ion irradiation with lower energy, no surface morphology change was found with a current density higher than 2.6 × 10² nA/cm² and an ion fluence up to 4 × 10¹⁶ ion/cm². However, Xe⁺ irradiation with a lower current density and a higher ion fluence led to topography development for all of the polymers. The roughness of the polymer surface increased, and well‐defined patterns appeared. The surface roughness increased with ion irradiation fluence and with the decrease of the current density. A pattern orientation along the beam direction was visible for inclined incidence between 15° and 45° with respect to the surface normal. Orientation was not seen at normal incidence. The surface topography development could be explained on the basis of the balance between surface damage and sputtering induced by the primary ion beam and redeposition–adsorption from the gas phase. Time‐of‐flight secondary ion mass spectrometry analyses of irradiated PS showed strong surface modifications of the molecular structure and the presence of new material. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 314–325, 2001     

Nanoporous membranes by cooperative self‐assembly of functionalized SEBS and titania

Sol–gel chemistry was adeptly exploited to fabricate nanoporous membranes by cooperative self‐assembly of modified triblock copolymer (SEBS‐NH₂) and titania network. Reinforcement of the matrix was achieved by hydrolytic condensation of tetraisopropoxytitanate without/with compatiblizing agent (3‐glycidyloxypropyl triethoxysilane), yielding two hybrid systems. Incorporation of different proportions of TiO₂ provoked well‐built variations in morphology of compatiblized SEBS‐NH₂/TiO₂ nanocomposites. At low titania loading, spherical nanoparticles were found well‐dispersed in regimented triblock domains while addition of higher amounts of TiO₂ generated nanoporous membranes by mutual self‐assembling of matrix and the reinforcement. Relative improvement of tensile and thermal properties over uncompatiblized nanocomposites was observed owing to enhanced interfacial interactions. Eventually, a combination of the two phases (17.5 wt. % titania in SEBS‐NH₂) demonstrated ample mechanical reinforcement, thermal and morphological profiles, ensuing robust self‐assembled nanostructures. Forthcoming prospects are envisioned as well. Copyright © 2013 John Wiley & Sons, Ltd.     

Nucleation and growth of Ge nanoclusters on the Si(111)‐(7 × 7) surface studied by scanning tunneling microscopy

Nucleation and growth of two‐dimensional Ge nanoclusters on the Si(111)‐(7 × 7) surface at elevated substrate temperatures have been studied using scanning tunneling microscopy. The uniformity of the Ge nanoclusters is improved with the increase of substrate temperature, and ordered Ge nanoclusters are formed on the faulted and unfaulted halves of (7 × 7) unit cell at substrate temperature of 200 °C. It is proposed that the Ge nanoclusters consist of six Ge atoms with three on top of the center adatoms and others on the rest atoms within one half of a unit cell. Copyright © 2014 John Wiley & Sons, Ltd.     

Process study of thermal plasma chemical vapor deposition of diamond,part II: Pressure dependence and effect of substrate pretreatment

The effect of pressure during thermal plasma chemical vapor deposition of diamond films has been investigated for a pressure range from 100 to 760 Torr. The maximum growth rate in our experiments occurs at 270 Torr for substrate temperatures around 1000°C. The existence of an optimum pressure for diamond deposition may he related to the balance between generation and recombination of atomic hydrogen and carbon-containing active species in front of the substrate. To estimate the concentrations of atomic hydrogen and methyl radicals under thermal plasma conditions, calculations based on thermodynamic equilibrium have been performed. This approximate evaluation provides useful guidelines because rapid diffusion results in a near frozen chemistry within the boundary layer. The effect of substrate pretreatment on diamond deposition depends on the type of substrate used. Two growth modes have been observed-layer growth and island growth of diamond crystals on various substrates. Screw dislocations have been observed in diamond deposition in thermal plasmas, and defects such as secondary nucleations are more concentrated along (III) directions than along (100) directions.     

Process study of thermal plasma chemical vapor deposition of diamond,part I: Substrate material,temperature, and methane concentration

Effects of process parameters on diamond film synthesis in DC thermal plasma jet reactors are discussed including substrate material, methane concentration and substrate temperature. Diamond has been deposited on silicon, molybdenum, tungsten, tantalum, copper, nickel, titanium, and stainless steel. The adhesion of diamond film to the substrate is greatly affected by the type of substrate used. It has been found that the methane concentration strongly affects the grain size of the diamond films. Increased methane concentrations result in smaller grain sizes due to the increased number of secondary nucleations on the existing facets of diamond crystals. Substrate temperature has a strong effect on the morphology of diamond films. With increasing substrate temperature, the predominant orientation of the crystal growth planes changes from the (111) to the (100) planes. Studies of the variation of the film quality across the substrate due to the nonuniformity of thermal plasma jets indicate that microcrystalline graphite formation starts at the corners and edges of diamond crystals when the conditions become unfavorable for diamond deposition.     

Medium energy,heavy and inert ion irradiation of metallic thin films: studies of surface nano‐structuring and metal burrowing

In context to the ion induced surface nanostructuring of metals and their burrowing in the substrates, we report the influence of Xe and Kr ion‐irradiation on Pt:Si and Ag:Si thin films of ~5‐nm thickness. For the irradiation of thin films, several ion energies (275 and 350 keV of Kr; 450 and 700 keV of Xe) were chosen to maintain a constant ratio of the nuclear energy loss to the electronic energy loss (S_n/S_e) in Pt and Ag films (five in present studies). The ion‐fluence was varied from 1.0 × 10¹⁵ to 1.0 × 10¹⁷ ions/cm². The irradiated films were characterized using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images show ion beam induced systematic surface nano‐structuring of thin films. The surface nano‐structures evolve with the ion fluence. The RBS spectra show fluence dependent burrowing of Pt and Ag in Si upon the irradiation of both ion beams. At highest fluence, the depth of metal burrowing in Si for all irradiation conditions remains almost constant confirming the synergistic effect of energy losses by the ion beams. The RBS analysis also shows quite large sputtering of thin films bombarded with ion beams. The sputtering yield varied from 54% to 62% by irradiating the thin films with Xe and Kr ions of chosen energies at highest ion fluence. In the paper, we present the experimental results and discuss the ion induced surface nano‐structuring of Pt and Ag and their burrowing in Si. Copyright © 2016 John Wiley & Sons, Ltd.     

Improving the gas barrier,mechanical and thermal properties of poly(vinyl alcohol) with molybdenum disulfide nanosheets

New multifunctional materials with both high structural and gas barrier performances are important for a range of applications. Herein we present a one‐step mechanochemical process to prepare molybdenum disulfide (MoS₂) nanosheets with hydroxy functional groups that can simultaneously improve mechanical strength, thermal conductivity, and gas permittivity of a polymer composite. By homogeneously incorporating these functionalized MoS₂ nanosheets at low loading of less than 1 vol %, a poly(vinyl alcohol) (PVA) polymer exhibits elongation at break of 154%, toughness of 82 MJ/m³, and in‐plane thermal conductivity of 2.31 W/m K. Furthermore, this composite exhibits significant gas barrier performance, reducing the permeability of helium by 95%. Under fire condition, the MoS₂ nanosheets form thermally stable char, thus enhancing the material's resistance to fire. Hydrogen bonding has been identified as the main interaction mechanism between the nanofillers and the polymer matrix. The present results suggest that the PVA composite reinforced with 2D layered nanomaterial offers great potentials in packaging and fire retardant applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 406–414     

Synthesis,thermal properties and crystalline morphology of poly(trimethylene terephthalate)/ZnO nanocomposites prepared by dual in situ polymerization

Poly(trimethylene terephthalate)/ZnO nanocomposites were successfully prepared by dual in situ polymerization. Firstly, ZnO nanoparticles were synthesized by a simple polyol method using 1,3‐propanediol (PDO) as solvent and stabilizer. Then, PTT/ZnO nanocomposites were prepared by in situ polymerization. The results of Fourier transform infrared spectra showed that PTT molecular chains were grafted to the surface of ZnO nanoparticles. The results of ¹H NMR spectra confirmed that propyl ester molecules (as reaction product) were incorporated into PTT molecular chains. It was found that the intrinsic viscosity and molecular weight of synthesized PTT decreased with the addition of ZnO nanoparticles and the incorporation of propyl ester molecules. TEM results showed that ZnO nanoparticles with particle size of 20 ~ 30 nm were well dispersed and fully distributed in the polymer matrix. Besides, the melting temperatures and crystallization temperature decreased gradually and then increased slightly with the increasing loading of ZnO nanoparticles. Because of the strong interaction between ZnO nanoparticles and PTT matrix, the thermal stability of PTT/ZnO nanocomposites was improved. Interestingly, the results of Polarized Optical Microscopy showed that banded spherulites morphology can be observed in all PTT/ZnO nanocomposite samples. However, at higher loading of ZnO nanoparticles, band spacing became larger and was finally disturbed. Copyright © 2016 John Wiley & Sons, Ltd.     

Metal‐conducting polymer interface studied by Kelvin probe microscopy: Au and Al on poly(3‐octyl‐thiophene)

In this work, we report a Kelvin probe microscopy investigation on the structural and electronic properties of gold and aluminum thin films evaporated on poly(3‐octyl‐thiophene) films. Our experimental setup allows us to perform scanning force microscopy (SFM) studies of the same area even if the sample is taken out of the SFM system for different processes (Au and Al evaporation). This allows a detailed study of the effect of adsorbed metal particles on the morphology and electrical properties of polymer thin films at the nanoscale. We found different behavior for both metals in morphology and electrical properties at the interface. These results can contribute to explain what happens at the metal–polymer interface of the devices when the metal contacts are grown. Thereby the observed nanoscale structural changes can be correlated with the overall performance of the fabricated devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1083–1093     

Phosphorus‐containing polyamide Mg(OH)2 nanocomposite coating on surface of poly(vinyl chloride) thin film: Study on thermal stability,flammability, and mechanical properties

Surface of poly(vinyl chloride) (PVC) thin films was coated using DOPO‐based polyamide (DBPA) coating and DBPA/Mg(OH)₂ nanocomposites (DBPN) coating by dip‐coating process. For this purpose, a new DOPO‐based dicarboxylic acid (DBDA) was synthesized and used for preparation of DBPA and organically surface modification of Mg(OH)₂ nanoparticles. The effects of DBPA and DBPN coatings on the morphology, thermal stability, combustion, and mechanical properties of PVC were investigated. The uniform dispersion of Mg(OH)₂ nanoparticles (nano‐MDH) and organically coating manner on the surface of the PVC films were confirmed by ATR‐IR spectroscopy, X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray, and elemental mapping. From thermal gravimetry analysis (TGA) results, the 10 mass% loss temperature (T₁₀) increased from 268°C to 272°C in PVC coated with DBPA‐containing 10 mass% of modified Mg(OH)₂ (MMH). Also the char residue, first and second mass loss temperatures of all PVC coated were increased compared with the neat PVC film. According to microscale combustion calorimetry (MCC) results, the peak of heat release rate (pHHR) and total heat release (THR) were decreased from 128 ± 2 to 69 W/g and 12 ± 1 to 4 ± 2 KJ/g for PVC film coated with DBPA‐containing 10 mass% of MMH, compared with the neat PVC. From tensile test results, tensile strength was increased from 31.78 ± 0.8 to 39.64 ± 0.9 MPa for PVC coated with polyamide‐containing 5 mass% of MMH compared with the neat PVC.