Deposition Of Polymer Films Research Articles

(Invited) The Potential of Pulsed Low Temperature Plasmas for the Controlled Deposition of Plasma Polymer Ultrathin Films and Composite Nanomaterials (Invited)

Low temperature discharges with their unique non-equilibrium properties are often used in industrial processes for the deposition of ultra-thin (plasma) polymer films. Applications for this type of thin films range from protective coatings to their use in membranes, biosensors and batteries. However, the properties of these thin films are highly dependent on the choice of discharge parameters, both in terms of their surface topography and their chemical composition. This paper deals with the great potential of pulsed discharges for the controlled deposition of plasma polymer films. The influence of pulse frequency and duty cycle on the deposition process and the properties of the resulting thin films is discussed from a theoretical point of view and is illustrated by experimental results. The latter concern examples of experiments carried out with discharges operated with acetylene or aniline, as well as functional coatings on top of MoS2, 2D graphene or CNTs. The work was supported by the project PEGASUS (Plasma Enabled and Graphene Allowed Synthesis of Unique nano-structures), funded by the European Union’s Horizon research innovation program under Grant Agreement No. 766894; EU Graphene Flagship FLAG-ERA III JTC 2021 project VEGA (No. PR-11938) Project-ANR-21-GRF1-0004. Further support was obtained via ARD MATEX Centre-Val de Loire Region (projects Carbon2 and Carbon3) and project Orleans Metropole (both France).

Multidimensional analysis of textiles coated with electroactive polymers for actuators

This paper presents a multidimensional analysis of textiles coated with conductive polymers for actuators. The purpose of using multidimensional scaling analysis is to compare similarities and dissimilarities between conductive textiles obtained through conductive polymeric film deposition to observe the optimal value for electrical resistance and to select an adequate method to achieve conductive fabric using different polymers (polyethylene glycol, polyvinyl alcohol or polyvinylidene fluoride) and metal microparticles (copper or nickel). The multidimensional analysis is based on mapping a series of material properties from a proximity matrix (similarities or dissimilarities) between these properties. Multidimensional scaling allows rebuilding the exact map of the values (within approximately a symmetry or rotation). To fit dissimilarity or similarity matrices for multiple variables into one common space estimating the weight parameters for each variable, the INDSCAL model (individual differences multidimensional scaling) was used.

SAW Humidity Sensing with rr-P3HT Polymer Films.

In the present paper the humidity sensing properties of regioregular rr-P3HT (poly-3-hexylthiophene) polymer films is investigated by means of surface acoustic wave (SAW) based sensors implemented on LiNbO3 (1280 Y-X) and ST-quartz piezoelectric substrates. The polymeric layers were deposited along the SAW propagation path by spray coating method and the layers thickness was measured by atomic force microscopy (AFM) technique. The response of the SAW devices to relative humidity (rh) changes in the range ~5-60% has been investigated by measuring the SAW phase and frequency changes induced by the (rh) absorption in the rr-P3HT layer. The SAW sensor implemented onto LiNbO3 showed improved performance as the thickness of the membrane increases (from 40 to 240 nm): for 240 nm thick polymeric membrane a phase shift of about -1.2 deg and -8.2 deg was measured for the fundamental (~78 MHz operating frequency) and 3rd (~234 MHz) harmonic wave at (rh) = 60%. A thick rr-P3HT film (~600 nm) was deposited onto the quartz-based SAW sensor: the sensor showed a linear frequency shift of ~-20.5 Hz per unit (rh) changes in the ~5-~50% rh range, and a quite fast response (~5 s) even at low humidity level (~5% rh). The LiNbO3 and quartz-based sensors response was assessed by using a dual delay line system to reduce unwanted common mode signals. The simple and cheap spray coating technology for the rr-P3HT polymer films deposition, complemented with fast low level humidity detection of the tested SAW sensors (much faster than the commercially available Michell SF-52 device), highlight their potential in a low-medium range humidity sensing application.

Polymerization mechanisms of hexamethyldisiloxane in low-pressure plasmas involving complex geometries

Hexamethyldisiloxane (HMDSO) low-pressure plasmas are known for their versatility in the deposition of plasma polymer films (PPFs) with different properties and applications. Although they have been studied for decades, the reaction mechanisms of plasma polymer formation leave open questions, particularly when deposition on 3D materials with complex geometries such as cavities and undercuts is considered. In the present study, two configurations named “cavity” and “undercut” have been selected to study the influence of diffusion of film-forming species and surface reactivity in HMDSO plasmas without and with O2 admixture. A varying spatial chemical composition of the plasma polymer deposit along the penetration depth of the studied configurations indicates different sticking probabilities of the film-forming species. Furthermore, although ion-induced effects are usually only considered for direct plasma exposure, the obtained results and additional etching experiments reveal that the contribution of high-energy particles might still be considered underneath small openings. Finally, the relevance of oxidizing chemical reactions at the surface inside the configurations is clarified when O2 is added to the plasma.

Molecular dynamics simulation of amine formation in plasma-enhanced chemical vapor deposition with hydrocarbon and amino radicals

Molecular dynamics simulations were performed to examine the amine formation in carbon-based polymer films deposited by plasma-enhanced chemical vapor deposition (PECVD) with methane (CH4) and nitrogen (N2) gases. In the simulations, the interactions between the deposited film surface and incident precursors were examined, where nitrogen species were assumed to be supplied only as amino radicals (NH2) such that the amount of primary amine (−NH2) could be maximized in the deposited film. Carbon was supplied as CH2 or CH3 radicals as well as CH2+ or CH3+ ions with an ion kinetic energy up to 100 eV, as typical in such PECVD experiments. It has been found that, even under such “ideal” conditions for the maximum primary-amine content, hydrogen (H) atoms of incident NH2 radicals tend to be transferred to surrounding C atoms in the polymerization process, leaving a relatively small amount of primary amine (the concentration ratio of primary amino groups NH2 to nitrogen atoms N ∼10%) in the deposited polymer films. The simulation results indicate that an increase of NH2 radicals in the gas phase of PECVD hardly increases the primary-amine content in the deposited films and, therefore, the primary-amine content may not depend strongly on the plasma conditions as long as a sufficient amount of nitrogen and hydrogen is supplied during the plasma polymerization process. The primary-amine content predicted by the simulations was found to be consistent with earlier experimental observations.

Electrochemical, optical and electrochromic properties of fused polydithienothiophene: A stable material with reversible doping

Fused-thiophene-based conjugated materials have received great importance due to their rigid and planar structure, enhancing the performance of electronic devices. We herein report the electrochemical synthesis of polydithieno[3,2-b:2′,3′-d]thiophene (PDTT) on different working electrodes (platinum, glassy carbon and ITO-coated glass) as well as on flexible ITO-coated PET electrode. We used both potentiodynamic and potentiostatic electropolymerization methods for the deposition of polymer films using TBAClO4/MeCN electrolyte-solvent system. The chemical and physical properties of the obtained polymer PDTT were characterized by FTIR, cyclic voltammetry, electrochemical impedance spectroscopy, UV–vis–NIR spectrophotometer and FESEM. The color of the film was red-orange in neutral form and transmission blue-grey in oxidized form. We explored the properties of PDTT in terms of electrochemical, optical and morphological stability, adhesion and chemical doping-dedoping. Further, the electrochromic behavior of the polymer films is presented at different wavelengths, and the coloration efficiency of 156.5 cm2C−1 and the maximum optical contrast of 26.4 % were recorded in the visible region. Finally, density functional theory (DFT) calculations on PDTT and its monomer were performed to understand the structure and energy levels and further compared with the experimental results.

Plasma-Enhanced Molecular Layer Deposition of Phosphane–Ene Polymer Films

A vapor-phase molecular layer deposition (MLD) process generating phosphorus-rich phosphane–ene polymer networks was adapted from known solution-phase methods and successfully used in a commercial atomic layer deposition tool. By using plasma-enhanced MLD on Si/SiO2 and Al2O3 substrates, film deposition was carried out with a commercially available primary phosphine, iBuPH2, paired with a known volatile cyclic siloxane precursor, tetramethyltetravinylcyclotetrasiloxane (D4Vinyl). The deposition process used radicals generated by an Ar plasma source to facilitate P–H addition to vinyl functionalities on D4Vinyl which yielded a growth per cycle of 0.6–2.0 Å, generating 10–120 nm films as determined by atomic force microscopy and scanning electron microscopy measurements. Characterization of the films were carried out using X-ray photoelectron spectroscopy, and oxygen scavenging capabilities were studied using a quartz crystal microbalance, showing an uptake of oxygen by a 12 nm depth of a freshly deposited polymer film.

Photogenerated charge separation at BiVO4 photoanodes enhanced by a Ag-modified porphyrin polymer skeleton.

Bismuth vanadate (BiVO4) has been considered a promising photoactive material in photoelectrochemical (PEC) water-splitting systems. However, the performance of BiVO4-based photoanodes is currently unsatisfactory, indicating the need for new architectural designs to improve their efficiency. In this paper, a porphyrin-phosphazene polymer (THPP-HCCP) was synthesized with a sizeable conjugated structure, and Ag particles were deposited on its surface as an organic-inorganic composite interface improvement layer. The deposition of the composite polymer film on BiVO4 resulted in a significant increase in photocurrent density, reaching up to 2.2 mA cm-2 (1.23 V vs. RHE), almost three times higher than pristine BiVO4, which benefits from the synergistic effect of Ag nanoparticles and porphyrin-phosphazene. Furthermore, photophysical and intensity-modulated photocurrent analysis demonstrated that the Ag-THPP-HCCP heterostructures could broaden the light-absorbing range and facilitate hole transfer to the semiconductor surface, resulting in an improved water oxidation process. The dynamic charge transport behavior of Ag-THPP-HCCP/BiVO4 was investigated using scanning photoelectrochemical microscopy, which showed that the rate constant (Keff) exhibits an almost 4-fold increase compared to pristine BiVO4, indicating a significant improvement in the transport of photogenerated holes. This experiment presents a novel strategy for designing high-efficiency polymer-based photoanodes.

FEATURES OF PLASMA COMPOSITION AND FLUORINE ATOM KINETICS IN CHF3 + O2 GAS MIXTURE

The effects of initial composition of CHF3 + O2 gas mixture on electro-physical plasma parameters, steady-state densities of active species and fluorine atom kinetics were investigated under the condition of constant gas pressure and input power. The combination of plasma diagnostics by Langmuir probes and model-based analysis of plasma chemistry confirmed known from previous work features of plasma composition in the absence of oxygen (in particular, the domination of HF molecules in a gas phase) as well as demonstrated how the oxygen influences steady-state densities of neutral species through kinetics of both electron-impact and atom-molecular reactions. It was shown that the addition of O2 with a proportional decrease in the content of CHF3 a) results in noticeable changes in electrons- and ions-related plasma parameters (electron temperature, electron density, ion flux); b) provides the effective conversion of fluorocarbon radicals (CHFx, CFx) into such compounds as CFxO, FO and COx; and b) causes an increase in the fluorine atom density up to 50% O2. The last phenomenon contradicts with the change in the total F atom formation rate, but reflects a decrease of their loss frequency in the reaction family of CHFx + F → CFx + HF. The model-based analysis of heterogeneous process kinetics was carried out using the set of tracing parameters based on gas-phase plasma characteristics. It was found that the addition of oxygen lowers the plasma polymerizing ability through both decreasing flux of polymerizing species and accelerating the oxidative destruction of deposited polymer film.

Visualization Methods of Latent Fingerprints on Metal Substrates/Cartridges

Despite the development of DNA analysis methods, fingerprint comparisons are still the most common and credible way to identify people when clarifying crimes and other forensically relevant events. Visualization of fingerprints applied to a metal surface, which may be curved (most often cartridges), often represents a difficult task, so that new methods are constantly being developed to get a high-quality visibility of fingerprints. This work describes the most important methods of visualization of fingerprints applied on metal substrates and especially on cartridge cases. So far, there is no suitable technique for making fingerprints visible on fired cartridges. Gun blue techniques, combined techniques with cyanoacrylate and, more recently, electrochemical deposition of polymer films potentiostatically or by cyclic voltammetry, which are fast, cheap and usable in the field, represent a promi­sing way.

Polypyrrole film synthesis via solution plasma polymerization of liquid pyrrole

Herein, a polymerization method is presented for forming polypyrrole films from liquid pyrrole using a solution plasma process (SPP) by adjusting the operating voltage waveform. Negatively or positively biased bipolar square-wave pulses were applied to a tungsten wire to generate plasma, while a copper tape served as a ground electrode as well as the metallic substrate for polymer film deposition. Solution plasma induced by negatively or positively biased bipolar square-wave pulses was mainly generated in the negative or positive half cycle of the operating voltage, respectively. Pyrrole anions, well known as strong bases, were generated by the SPP using the negatively biased bipolar square-wave pulse, which increased the pH level of the SP-processed pyrrole solution. The polypyrrole films were deposited onto the Cu tape, which served as the anode, only under this operation condition. Thereafter, the polypyrrole film, with a thickness of 22 µm and consisting of overlapped polypyrrole particles, was synthesized for 2 h. The differences in the discharge characteristics of the solution plasma driven by negatively and positively biased bipolar square-wave pulses initiated the formation of different reactive species of the pyrrole monomer. Based on these results, a mechanism for polypyrrole film formation using the SPP is proposed.

Research trends in the development of anodes for electrochemical oxidation of wastewater

Abstract The review focuses on the recent development in anode materials and their synthesis approach, focusing on their compatibility for treating actual industrial wastewater, improving selectivity, electrocatalytic activity, stability at higher concentration, and thereby reducing the mineralization cost for organic pollutant degradation. The advancement in sol–gel technique, including the Pechini method, is discussed in the first section. A separate discussion related to the selection of the electrodeposition method and its deciding parameters is also included. Furthermore, the effect of using advanced heating approaches, including microwave and laser deposition synthesis, is also discussed. Next, a separate discussion is provided on using different types of anode materials and their effect on active •OH radical generation, activity, and electrode stability in direct and indirect oxidation and future aspects. The effect of using different synthesis approaches, additives, and doping is discussed separately for each anode. Graphene, carbon nanotubes (CNTs), and metal doping enhance the number of active sites, electrochemical activity, and mineralization current efficiency (MCE) of the anode. While, microwave or laser heating approaches were proved to be an effective, cheaper, and fast alternative to conventional heating. The electrodeposition and nonaqueous solvent synthesis were convenient and environment-friendly techniques for conductive metallic and polymeric film deposition.

Vapor Deposition of Silicon-Containing Microstructured Polymer Films onto Silicone Oil Substrates.

In this study, a silicon-containing cross-linked polymer, poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane-co-ethylene glycol diacrylate) (p(V4D4-co-EGDA)), was deposited onto high-viscosity silicone oil using initiated chemical vapor deposition (iCVD). The ratio of the feed flow rate of V4D4 to EGDA was systematically studied, and the chemical composition and morphology of the top and bottom surfaces of the films were analyzed. The films were microstructured, and the porosity and thickness of the films increased with increasing V4D4 content. The top of the film was composed of densely packed and loosely packed microstructured regions. X-ray photoelectron spectroscopy on the top and bottom surfaces of the films showed a heterogeneous chemical composition along the thickness of the film, with higher silicon content on the top surface compared to that on the bottom surface. To the best of our knowledge, this is the first study of iCVD deposition of a silicon-containing polymer film onto silicone oil. The results of this study can be used for the synthesis of polymer precursor films for the fabrication, via pyrolysis, of silicon-based inorganic membranes for use in hydrogen production using silicone oil to prevent infiltration of monomer into the underneath membrane support structure during vapor deposition.

Electropolymerized durable coatings deposited onto Pt-electrode as corrosion inhibitor for mild steel

Electropolymerization and deposition of poly(salicylic acid-co-N-methylaniline) copolymer, poly(SA-co-NMA) onto platinum electrode was studied using cyclic voltammetry in an acidic medium under inert conditions at various reaction factors. The mechanism of the electropolymerizaion reaction was proposed and the apparent activation energy (E app) was determined. The deposited polymer film was characterized using different spectral tools such as UV spectroscopy, IR, 1HNMR, X-ray, thermogravimetric analysis (TGA) and scanning electron microscopic (SEM) analysis, the spectral data for poly(salicylic acid) PSA and poly(N-methylaniline) PNMA were also given for comparison. The electropolymerized co-polymer was collected from the Pt-surface then it has been investigated as a corrosion inhibitor. An open circuit potential method (OCP), electrochemical impedance spectroscopy (EIS) measurements and polarization techniques were used to study the application and the efficiency of the deposited copolymer film as corrosion inhibitor for mild steel in an acidic environment pH = 2.

A Cathodic Electrochromic Material Based on Thick Perylene Bisimide Film with High Optical Contrast and High Stability

A Cathodic Electrochromic Material Based on Thick Perylene Bisimide Film with High Optical Contrast and High Stability

Deposition of nano-scale polymer film on micro-fins to enhance the film-wise condensation of very low surface tension substances

Dropwise condensation is extremely difficult to accomplish through the nanostructured surfaces for very low surface tension substances, such as the Freon refrigerants. To further improve the laminar film condensation heat transfer of the substances with very low surface tension, rely solely on the super hydrophobic layer might not work. In this work, a three dimensional micro-finned tube was fabricated and a layer of polymer coating was deposited outside the fins. Condensation of two substances, R1234ze(E) and R134a, were investigated at saturation temperature 30 and 40℃. Under the coupling effect of coating and fins, the condensing heat transfer coefficient can be up to 28 times larger than the smooth tube and the value can reach 43 kW/m2K at heat flux 20 kW/m2. In the lower heat flux, it can be 150% higher than the same finned tube without polymer coating. As the condensing heat transfer enhancement with only fin structure modifications would soon reach its limit, it should have a good application prospect for the micro-fins with surface treatment.

Poly(V3D3), an iCVD polymer with promising dielectric properties for high voltage capacitors

This paper presents a study of the physicochemical and the dielectric characteristics of capacitor structures, with an organosilicate polymer fabricated by initiated chemical vapor deposition as dielectric. The polymer evaluated is the poly(trivinyltrimethylcyclotrisiloxane), and a comparative study on different bottom electrodes was performed. Preliminary results demonstrate that iCVD technique permits the deposition of low roughness, low defect and uniform polymer films, and the dielectric fabricated exhibits a high breakdown field and an original dielectric behaviour, which makes it a prominent candidate for high voltage 3D capacitors.

A Versatile Surface Modification Method via Vapor-phase Deposited Functional Polymer Films for Biomedical Device Applications.

For last two decades, the demand for precisely engineered three-dimensional structures has increased continuously for the developments of biomaterials. With the recent advances in micro- and nano-fabrication techniques, various devices with complex surface geometries have been devised and produced in the pharmaceutical and medical fields for various biomedical applications including drug delivery and biosensors. These advanced biomaterials have been designed to mimic the natural environments of tissues more closely and to enhance the performance for their corresponding biomedical applications. One of the important aspects in the rational design of biomaterials is how to configure the surface of the biomedical devices for better control of the chemical and physical properties of the bioactive surfaces without compromising their bulk characteristics. In this viewpoint, it of critical importance to secure a versatile method to modify the surface of various biomedical devices. Recently, a vapor phase method, termed initiated chemical vapor deposition (iCVD) has emerged as damage-free method highly beneficial for the conformal deposition of various functional polymer films onto many kinds of micro- and nano-structured surfaces without restrictions on the substrate material or geometry, which is not trivial to achieve by conventional solution-based surface functionalization methods. With proper structural design, the functional polymer thin film via iCVD can impart required functionality to the biomaterial surfaces while maintaining the fine structure thereon. We believe the iCVD technique can be not only a valuable approach towards fundamental cell-material studies, but also of great importance as a platform technology to extend to other prospective biomaterial designs and material interface modifications for biomedical applications.

Permeation‐resistant and flexible plasma‐polymerised films on 2‐hydroxyethyl methacrylate hydrogels

AbstractThis study focuses on the deposition of plasma polymer films (PPFs) on hydrogels that could act as permeation barriers for aqueous species. The deposited PPFs on hydrogels were studied in terms of their ability to resist the permeation of an aqueous dye molecule after 24‐h exposure to an aqueous solution and mechanical stress. Permeation of the dye toluidine blue O through the hydrogels after plasma polymerisation was at least 75% less than that through an untreated hydrogel. The X‐ray photoelectron spectroscopy analysis showed introduction of O‐ and N‐rich chemical functionalities in the surface chemical composition of the hydrogel after plasma polymerisation. Scanning electron microscope imaging pointed out that milder plasma conditions result in uniform films that do not degrade upon exposure to water or mechanical stress.

Physical supercritical fluid deposition of polymer films: controlling the crystallinity with pressure

The self-assembly of isotactic polypropylene films from supercritical n-pentane was studied. The effects of solution thermodynamics and fluid mechanics were reported.