Plasma-assisted Polymerization Research Articles

A manual operated and eco-friendly plasma-assisted polymerization method for enhancing surface weather resistance of insulation

With the increasing demand for high-voltage long-distance power transmission, insulation as the first protection of power system, faces serious challenges from material degradation caused by moisture invading, surface contamination and pollution flashover. Addressing the issue requires significant effort and may cause harmful by-product emission from large-scale wet type material processing. In this work, a novel eco-friendly dry treatment method based on manual operated Air/Alkoxysilane(PMDMS)/plasma is developed to enhance weather resistance and electrical performances of contaminated insulation. Tiny amounts of harmless reaction medium are transmitted to plasma through controllable air bubbling, and it implements precise dry type processing on material surface. Plasma pulverizes pre-existing contamination and synchronously activates hydrolysis-polymerization of PMDMS to deposit Si-containing protection layer (Si-O2, Si-CH3) on surface. It is demonstrated that the plasma treatment inhibits dirt pollution and electrical erosion of on-site 110 kV silicone rubber (SIR), and the electrical and hydrophobicity properties are both promoted. Flashover voltage increases from 4.65 to 8.71 kV, and water contact angle increases from 138.27° to 146.41°. Overall, this newly-developed dry portable plasma treatment strategy for insulation enhancement avoids environment pollution and economic losses, and provides a scalable avenue for on-site insulation recovery and service life prolonging.

Fast Photoactuation and Environmental Response of Humidity-Sensitive pDAP-Silicon Nanocantilevers.

Multi-responsive nanomembranes are a new class of advanced materials that can be harnessed in complex architectures for micro and nano-manipulators, artificial muscles, energy harvesting, soft robotics, and sensors. The design and fabrication of responsive membranes must meet such challenges as trade-offs between responsiveness and mechanical durability, volumetric low-cost production ensuring low environmental impact, and compatibility with standard technologies or biological systems This work demonstrates the fabrication of multi-responsive, mechanically robust poly(1,3-diaminopropane) (pDAP) nanomembranes and their application in fast photoactuators. The pDAP films are developed using a plasma-assisted polymerization technique that offers large-scale production and versatility of potential industrial relevance. The pDAP layers exhibit high elasticity with the Young's modulus of ≈7 GPa and remarkable mechanical durability across 20-80°C temperatures. Notably, pDAP membranes reveal immediate and reversible contraction triggered by light, rising temperature, or reducing relative humidity underpinned by a reversible water sorption mechanism. These features enable the fabrication of photoactuators composed of pDAP-coated Si nanocantilevers, demonstrating ms timescale response to light, tens of µm deflections, and robust performance up to kHz frequencies. These results advance fundamental research on multi-responsive nanomembranes and hold the potential to boost versatile applications in light-to-motion conversion and sensing toward the industrial level.

A new strategy to prevent biofilm and clot formation in medical devices: The use of atmospheric non-thermal plasma assisted deposition of silver-based nanostructured coatings.

In industrialized countries, health care associated infections, the fourth leading cause of disease, are a major health issue. At least half of all cases of nosocomial infections are associated with medical devices. Antibacterial coatings arise as an important approach to restrict the nosocomial infection rate without side effects and the development of antibiotic resistance. Beside nosocomial infections, clot formation affects cardiovascular medical devices and central venous catheters implants. In order to reduce and prevent such infection, we develop a plasma-assisted process for the deposition of nanostructured functional coatings on flat substrates and mini catheters. Silver nanoparticles (Ag NPs) are synthesized exploiting in-flight plasma-droplet reactions and are embedded in an organic coating deposited through hexamethyldisiloxane (HMDSO) plasma assisted polymerization. Coating stability upon liquid immersion and ethylene oxide (EtO) sterilization is assessed through chemical and morphological analysis carried out by means of Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In the perspective of future clinical application, an in vitro analysis of anti-biofilm effect has been done. Moreover, we employed a murine model of catheter-associated infection which further highlighted the performance of Ag nanostructured films in counteract biofilm formation. The anti-clot performances coupled by haemo- and cytocompatibility assays have also been performed.

Stability of oxygen-rich plasma-polymerized coatings in aqueous environment.

In this work, we report on the stability of oxygen-rich plasma-polymerized (pp) films in an aqueous environment. The pp films were deposited via atmospheric-pressure plasma jet treatment of polymerizable organic liquids. The monomers used for the plasma-assisted polymerization were tetrahydrofurfuryl methacrylate, 1,2,4-trivinylcyclohexane, and mixtures thereof. The pp films were deposited at different plasma input powers ranging from 3 to 7 W. The stability of the obtained pp films was studied upon long-time storage in pure water and in buffer solutions of pHs 4, 7, and 10. After 24 h of storage of the pp films in de-ionized water, all of the studied pp films experienced thickness losses along with the formation of various ringlike structures at their surface, whereas Fourier transformed infrared (FT-IR) analysis showed no changes in their chemical composition. The pp films stored in pH 10 were completely delaminated from the substrate surface, while the pp films stored for 24 h in pH 4 showed swelling behavior, partial delamination, and the formation of wrinkles at the coatings' surface. The pp films stored for 24 h in pH 7 experienced minor thickness losses and formation of wrinkles at their surface. FT-IR analysis of the pp films stored in buffer solutions of pH 4 and pH 7 showed a decrease of C=O and an increase of O-H stretching signals in all of the cases. The observed chemical changes corresponded to the hydrolysis of esters presented in the pp films' structure.

Composite Bilayer Polymer Membranes with Hydrophobic Layers

Bilayer composite membranes (CMs) are prepared by depositing a polymer layer onto track-etched polypropylene (PP) membrane by using plasma polymerization of hexamethyldisilazane (HMDSN). The chemical structure, wetting properties, and morphological characteristics of the prepared CMs are investigated. By depositing the plasma-polymerized polymer, we obtain CMs with two hydrophobic layers, of which one is the initial PP membrane, serving as a matrix. This layer has a water contact angle of 120°. The other layer, which was formed during plasma polymerization of HMDSN, contains nitrogen-containing functional groups, along with minor amounts of oxygen-containing, mainly carboxylic, groups. The water contact angle of this layer is ~98°. Deposition of a polymer film by plasma-assisted polymerization results in smoothing surface asperities of the initial (matrix) membrane, a considerable decrease in pore diameter, and alteration of pore shape; namely, the pores acquire an asymmetric (conical) profile.

Evaluation of mechanism of cold atmospheric pressure plasma assisted polymerization of acrylic acid on low density polyethylene (LDPE) film surfaces: Influence of various gaseous plasma pretreatment

Owing to its exceptional physiochemical properties, low density poly ethylene (LDPE) has wide range of tissue engineering applications. Conversely, its inadequate surface properties make LDPE an ineffectual candidate for cell compatible applications. Consequently, plasma-assisted polymerization with a selected precursor is a good choice for enhancing its biocompatibility. The present investigation studies the efficiency of plasma polymerization of acrylic acid (AAC) on various gaseous plasma pretreated LDPE films by cold atmospheric pressure plasma, to enhance its cytocompatibility. The change in chemical composition and surface topography of various gaseous plasma pretreated and acrylic deposited LDPE films has been assessed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The changes in hydrophilic nature of surface modified LDPE films were studied by contact angle (CA) analysis. Cytocompatibility of the AAC/LDPE films was also studied in vitro, using RIN-5F cells. The results acquired by the XPS and AFM analysis clearly proved that cold atmospheric pressure (CAP) plasma assisted polymerization of AAC enhances various surface properties including carboxylic acid functional group density and increased surface roughness on various gaseous plasma treated AAC/LDPE film surfaces. Moreover, contact angle analysis clearly showed that the plasma polymerized samples were hydrophilic in nature. In vitro cytocompatibility analysis undoubtedly validates that the AAC polymerized various plasma pretreated LDPE films surfaces stimulate cell distribution and proliferation compared to pristine LDPE films. Similarly, cytotoxicity analysis indicates that the AAC deposited various gaseous plasma pretreated LDPE film can be considered as non-toxic as well as stimulating cell viability significantly. The cytocompatible properties of AAC polymerized Ar + O2 plasma pretreated LDPE films were found to be more pronounced compared to the other plasma pretreated AAC/LDPE films.

Plasma Solutions for Life Sciences and Medical Device Manufacturing

The medical device industry is highly regulated which demands reliable and reproducible components and manufacturing processing to satisfy said regulators. Regulated devices range from a simple bandage to the most complex implantable heart defibrillator. Developing these devices requires rigorous testing and validation of the materials and processes used to manufacture them. Challenges abound due to issues with bio-compatibility, material mismatch, implant duration, ability to withstand sterilization, wettability, lubricity, and so on. Plasma processes address many of these challenges while enabling more reliable and robust devices. Plasma has been shown to enhance surface wettability, remove surface contamination, improve bondability and maintain the bulk properties of the material treated. Medical diagnostics are highly dependent on reliable chemical analytic techniques where fluids are contacted with reagents in polymer containers such as microtiter plates or plated used in gene sequencing systems or chemiluminescence detection tools. The reliability of such techniques are dependent upon the repeatable wetting of the containers by the fluids and/or reagents. Plasma processing is an excellent choice for increasing the surface energy of polymers enabling more wettable surfaces.Because plasma treatment will enhance the surface energy of samples treated it is chosen prior to adhesive bonding, lubricious coating application, polymer coating application, device printing, etc. Plasma is also useful for depositing polymer films via plasma assisted polymerization. Plasma polymer films can be used to enhance adhesion of subsequent bonding steps and in certain cases forms an excellent tack reduction film when deposited on rubber compounds. Plasma is also utilized to remove surface contaminants that can interfere with subsequent bonding steps.Specific application examples will be presented showing the many uses and benefits of plasma processing for medical devices.

Hydrophilic–oleophobic coatings on cellulosic materials by plasma assisted polymerization in liquid phase and fluorosurfactant complexation

Materials with hydrophilic–oleophobic properties are of relevance due to their application to different fields such as self-cleaning coatings, liquid–liquid separation membranes and functional textiles for different technical applications. In this work, hydrophilic–oleophobic coatings have been deposited on cellulosic materials (filter paper and bleached cotton) by means of plasma assisted polymerization of acrylic acid solutions in water followed by cationic fluorosurfactant complexation. Chemical composition of the coatings on cellulosic materials was characterized by means of FTIR–ATR and XPS whereas their morphology was studied by SEM. Hydrophilic–oleophobic behavior was characterized by means of contact angle and wetting time. Additionally wetting properties of cationic, anionic and non-ionic surfactant solutions on the hydrophilic–oleophobic coatings were used to characterize the polyelectrolyte electrostatic forces upon the functionalized layer.

Coating of structured catalytic reactors by plasma assisted polymerization of tetramethyldisiloxane

An original process based on cold plasma assisted polymerization of tetramethyldisiloxane (TMDSO) in the presence of O2 was developed to cover substrates showing various shapes (plate and foam). In the frame of catalytic application, this coating has to act as a bonding layer for the deposition of active phase such as VOx/TiO2 well-known for its properties in NOx and volatile organic compounds abatement and in the production of chemical intermediates. Good results were obtained by the deposition of a 5-μm thick polysiloxane film followed by a thermal treatment under air at 650°C and by a remote nitrogen plasma post treatment. This procedure led to a silica-like layer allowing its coating in an aqueous suspension of TiO2. Such a multilayered material can be obtained homogeneously on the whole surface of a sample showing a 3D open geometry like metallic foam. Characterizations of the different steps of the elaborated multilayer material were performed by Fourier transformed infrared spectroscopy, Raman spectrometry, X-ray photoelectron spectroscopy, and electron probe micro-analyzer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Surface modification of CNFs via plasma polymerization of styrene monomer and its effect on the properties of PS/CNF nanocomposites

AbstractCarbon nanofibers (CNF) were modified via plasma assisted polymerization in a specially designed reactor. The effect of the plasma reactor conditions, such as power and time, on the extent of the CNFs modification was examined. Polystyrene (PS) coated nanofibers plus PS polymer were then processed in a Brabender torque rheometer mixing chamber to obtain PS/CNF nanocomposites, with 0.5, 1.0, 3.0, and 5.0 wt % of CNF. The effect of the plasma treatment on the dispersion of the nanofibers and on the compatibility between the nanofibers and the polymer matrix was also examined. Modification of the CNFs was assessed by measuring the contact angle of water in a “bed” of nanofibers and by examining its dispersion in several solvents. The morphology of PS/CNF nanocomposites was studied through scanning electron microscopy (SEM). Contact angles decreased in all cases, indicating a change in hydrophobicity of the modified CNFs. This change was confirmed in the CNF dispersion tests in several solvents. SEM micrographs show the difference between the original and the PS coated CNF. In addition, fractured samples show the effect of this treatment, in the sense that the CNF seem to be completely embedded in the polymer matrix, which clearly indicates the high compatibility between the PS and the modified (PS coated) CNF. As a consequence, a much better dispersion of the treated CNF was observed. Finally, the tensile modulus of PS/CNF composites increased slightly with respect to PS when using untreated CNFs, but more than doubled when using plasma treated CNFs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Chemical Structure and Properties of Plasma-Polymerized Maleic Anhydride Films

Plasma-assisted polymerization of maleic anhydride has been investigated under different experimental conditions. Significant variations in the film chemical structure and the film properties were obtained using pulsed plasma depositions operated at different duty cycles. The film chemical structures were obtained using X-ray photoelectron spectroscopy (XPS) and Fourier transform infra red spectroscopy (FT-IR). Surface derivatization reactions using decylamine and benzylamine were used to demonstrate their surface reactivity toward nucleophilic moieties and to change the surface free energy of the plasma polymer films, all of which are of particular interest for future applications in the attachment of biological molecules and cells. A method of substrate pretreatment was developed to ensure reliable binding between the substrate and the plasma polymer film in aqueous solution. Impedance spectroscopy was used to monitor polymer film changes in aqueous media. The hydrated films showed some resemblance to p...

Electronic Properties Study of Carbon Nanostructure

Amorphous conducting carbon films are prepared using plasma assisted polymerization process. SEM and TEM shows random aggregate-of globular clusters of micron size inside the samples. Electrical measurements indicate a near metallic nature. A tendency of saturation of resistivity at low temperature is observed. From spectroscopic analysis we find some unusual features. Based on these observations a structural model of this carbon is proposed.