Plasma Polymerization Treatment Research Articles

Thiolation of polycaprolactone (PCL) nanofibers by inductively coupled plasma (ICP) polymerization: Physical, chemical and biological properties

In this study, polycaprolactone (PCL) nanofibrous mats (Ø: 144.2 ± 3.4 nm) were fabricated by electrospinning and subsequently exposed to a low-pressure plasma polymerization treatment using 1-propanethiol as monomer. Surface characterization was performed utilizing several techniques: X-ray photoelectron spectroscopy (XPS) for surface chemical analysis, water contact angle (WCA) measurements for wettability examination, scanning electron microscopy (SEM) for morphological characterization as well as atomic force microscopy (AFM) for visualization of the topography of individual nanofibers before and after the plasma polymerization process. Moreover, the biocompatibility of the untreated and plasma-modified nanofibers was also evaluated by seeding bone marrow stem cells (BMSTs) on the samples and examining cell adhesion and proliferation using live/dead fluorescence imaging and MTT assays. The obtained results revealed that plasma exposure time significantly affected the morphology as well as the surface chemical composition of the electrospun mats, while surface wettability was largely maintained. A short exposure time of 5 s was found to maintain the advantageous nanofibrous morphology as only a very thin coating layer was deposited (range of a few nms), while longer exposure times resulted in a gradual loss of the nanofibrous structure due to the inhomogeneous deposition of thicker coatings. Moreover, also the sulphur amount was found to gradually increase with increasing exposure time resulting from the gradual growth of the deposited thiol-rich coating on the nanofibers with a maximum of 14% of sulphur, correlating with a 6.7% SH concentration after a plasma polymerization step of 1 min. As the nanofibrous structure is highly advantageous for cell growth, a 5 s plasma exposure time was selected for the cell studies, which proved that the deposition of a very thin thiol-rich coatings was able to positively affect BMSTs adhesion and proliferation. These enhanced cellular responses can be attributed to the presence of thiol groups on the nanofibers which are known to significantly increase the adhesion of culture medium proteins. It can thus be concluded that the incorporation of thiol functionalities via plasma polymerization can positively affect the cellular response of nanofibrous meshes and thus have large potential in tissue engineering applications.

Customizing the surface charge of thin-film composite membranes by surface plasma thin film polymerization

Solute-surface interactions are critical in membrane science and dominate a number of diffusion and selectivity parameters. In water treatment particularly, the charge on the membrane has been shown to affect ion transport selectivity as well as fouling mechanisms. The development of advanced surface technologies that allow for potential customization of the surface charge for specific applications, without compromising the essential performance of the membrane, is therefore desirable. In this paper, a novel plasma polymerization strategy was applied to commercial reverse osmosis membrane in order to tune the surface charge. Two monomers, maleic anhydride and vinylimidazole, were plasma polymerized onto the membrane resulting in a modification of the surface energy with resultant isoelectric points of approximately pH 3 and pH 7 respectively. This required only a short 5min plasma polymerization treatment in each case. Thus, in addition to enhancing the water permeation by up to 10%, in comparison to the reference membranes, the overall charge of the membranes was shifted from highly negatively charged upon maleic anhydride polymerization to highly positively charged upon vinylimidazole polymerization. A comprehensive morphological and chemical analysis was performed to correlate the changes to the presence of functional groups and the alteration of the surface texture. Short treatments were found to smooth the surface whilst enriching the surface with either carboxylic or amine/amide groups. This work opens new avenues to engineer advanced membranes with improved performance and selectivity.

Plasma polymer-functionalized silica particles for heavy metals removal.

Highly negatively charged particles were fabricated via an innovative plasma-assisted approach for the removal of heavy metal ions. Thiophene plasma polymerization was used to deposit sulfur-rich films onto silica particles followed by the introduction of oxidized sulfur functionalities, such as sulfonate and sulfonic acid, via water-plasma treatments. Surface chemistry analyses were conducted by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Electrokinetic measurements quantified the zeta potentials and isoelectric points (IEPs) of modified particles and indicated significant decreases of zeta potentials and IEPs upon plasma modification of particles. Plasma polymerized thiophene-coated particles treated with water plasma for 10 min exhibited an IEP of less than 3.5. The effectiveness of developed surfaces in the adsorption of heavy metal ions was demonstrated through copper (Cu) and zinc (Zn) removal experiments. The removal of metal ions was examined through changing initial pH of solution, removal time, and mass of particles. Increasing the water plasma treatment time to 20 min significantly increased the metal removal efficiency (MRE) of modified particles, whereas further increasing the plasma treatment time reduced the MRE due to the influence of an ablation mechanism. The developed particulate surfaces were capable of removing more than 96.7% of both Cu and Zn ions in 1 h. The combination of plasma polymerization and oxidative plasma treatment is an effective method for the fabrication of new adsorbents for the removal of heavy metals.

Development of Oxidized Sulfur Polymer Films through a Combination of Plasma Polymerization and Oxidative Plasma Treatment

A novel two-step process consisting of plasma polymerization and oxidative plasma treatment is introduced in this article for the first time for the fabrication of -SO(x)(H)-functionalized surfaces. Plasma-polymerized thiophene (PPT) was initially deposited onto silicon wafers and subsequently SO(x)(H)-functionalized using air or oxygen plasma. The effectiveness of both air and oxygen plasma treatments in introducing sulfur-oxygen groups into the PPT film was investigated as the plasma input specific energy and treatment time were varied. The surface chemistries of untreated and treated PPT coatings were analyzed by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS), whereas spectroscopic ellipsometry was used to evaluate the film thickness and ablation rate. Surface chemistry analyses revealed that high concentrations of -SO(x)(H) functionalities were generated on the surface upon either air or oxygen plasma treatment. It was found that, at low plasma input energies, the oxidation process was dominant whereas, at higher energies, ablation of the film became more pronounced. The combination of thiophene plasma polymerization and air/oxygen plasma treatment was found to be a successful approach to the fabrication of -SO(x)(H)-functionalized surfaces.

Repair of Abdominal Wall Defects In Vitro and In Vivo Using VEGF Sustained-Release Multi-Walled Carbon Nanotubes (MWNT) Composite Scaffolds

ObjectivePorcine acellular dermal matrices (ADM) have been widely used in experimental and clinical research for abdominal wall repair. Compared to porcine small intestinal submucosa (SIS), the effect of these matrices on the regenerative capacity of blood vessels is still not ideal. Multi-walled carbon nanotubes (MWNTs) can more effectively transport VEGF to cells or tissues because of their large specific surface area and interior cavity. In this study, we explored the safety and efficacy of implanted VEGF-loaded MWNT composite scaffolds in vitro and vivo to repair abdominal wall defects.Materials and MethodsVEGF-loaded MWNTs were prepared by a modified plasma polymerization treatment. Four composite scaffolds were evaluated for cytotoxicity, proliferation, and release dynamics. We created 3 cm×4 cm abdominal wall defects in 43 Sprague-Dawley rats. After implantation times of 2, 4, 8, and 12 weeks, the scaffolds and the surrounding tissues were collected and examined by gross inspection, biomechanical testing, and histological examination.ResultsA 5–10 nm poly(lactic-co-glycolic acid) (PLGA) film was evenly distributed on MWNTs. The 3% MWNT composite group showed lower cytotoxicity and appropriate release performance, and it was thus tested in vivo. In rats with the 3% composite implanted, host cells were prevented from migrating to the ADM at 2 weeks, vascularization was established more rapidly at 12 weeks, and the values for both the maximum load and the elastic modulus were significantly lower than in the ADM-alone group (p<0.01). Histological staining revealed that the MWNT was still not completely eliminated 12 weeks after implantation.ConclusionMWNTs were able to carry VEGF to cells or tissues, and the 3% MWNT composite material showed lower cytotoxicity and had an appropriate release performance, which prompted faster vascularization of the ADM than other scaffolds. Nevertheless, the MWNTs induced harmful effects that should be carefully considered in biomedical studies.

Surface modification of polyester and polyamide fabrics by low frequency plasma polymerization of acrylic acid

AbstractIn this study, the surface characteristics of polyester and polyamide fabrics were changed by plasma polymerization technique utilizing acrylic acid as precursor. This monomer was used to produce hydrophilic materials with extended absorbency. The hydrophilicity, total wrinkle recovery angle (WRA°) and breaking strength of the fabrics were determined prior and after plasma polymerization treatment. The modification of surfaces was carried out at low pressure (&lt;100 Pa) and low temperature (&lt;50°C) plasma conditions. The effects of exposure time and discharge power parameters were optimized by comparing properties of the fabrics before and after plasma polymerization treatments. It was shown that two sides of polyester fabric samples were treated equally and homogeneously in plasma reactor. For polyester fabrics, the minimum wetting time, 0.5 s, was observed at two plasma processing parameters of 10 W–45 min and 10 W–20 min, where untreated fabric has a wetting time of 6 s. For polyester fabrics, the maximum value was obtained at 60 W–5 min with the wrinkle recovery angle of 306° where the untreated fabric has 290°. The optimum plasma conditions for polyamide fabrics were determined as 30 W–45 min where 2 s wetting time was observed. Wrinkle recovery angle of untreated polyamide fabric was 264°. In this study, after plasma polymerization of acrylic acid, wrinkle recovery angle values were increased by 13%. No significant change was observed in breaking strength of both fabrics after plasma treatment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2318–2322, 2007

Dielectric Barrier Discharge at Atmospheric Pressure as a Tool to Deposit Versatile Organic Coatings at Moderate Power Input

AbstractPlasma coating technologies have been demonstrated as being promising for the fabrication of bioactive and biocompatible materials, among others. Reported efforts are exclusively focused on the two‐step approaches, in which the bioactive component is first immobilized on a substrate, followed by a (vacuum) plasma polymerization treatment or vice versa. However, we believe that upon minimizing the plasma energy, numerous bioactive substances such as enzymes and nucleic acids can be immobilized directly in plasmas via copolymerization with organic precursors, or by direct entrapment in the organic polymer. Therefore, a dielectric barrier discharge was employed at atmospheric pressure and ambient temperature to deposit organic coatings with reasonable growth rates at power input and frequency values as low as possible. Two promising precursors, acetylene and pyrrole, were selected out of 22 organic monomers for full physicochemical characterization. While the acetylene polymer film shows resemblance with its vacuum plasma analogue, polypyrrole coatings produced in vacuum and atmospheric plasmas differ significantly.magnified image

Effects of surface modification, carbon nanofiber concentration, and dispersion time on the mechanical properties of carbon‐nanofiber–polycarbonate composites

AbstractThe time effect of ultrasonication was investigated for dispersing carbon nanofibers (CNFs) into a polycarbonate (PC) matrix on the mechanical properties of thus‐produced composites. The effects of CNF surface modification by plasma treatment and the CNF concentration in composites on their mechanical properties were also explored. The plasma coating was characterized by HRTEM and FT‐IR. Furthermore, the plasma polymerization (10 w) treatment on the CNF enhanced the CNF dispersion in the polymer matrix. The mechanical properties of the CNF–PC composites varied with the dispersion time, at first increasing to a maximum value and then dropping down. After a long ultrasonic treatment (24 h), the properties increased again. At a high concentration, the CNF‐PC suspension became difficult to disperse. Additionally, the possible mechanisms for these behaviors are simply proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3792–3797, 2007

Surface modification and ultrasonication effect on the mechanical properties of carbon nanofiber/polycarbonate composites

The effect of plasma surface modification and ultrasonication time on the mechanical properties of multi-wall carbon nanofiber polycarbonate composites were investigated. The study showed that plasma polymerization treatment of multi-wall carbon nanofibers enhanced the dispersion of the nanofibers in the polymer, and hence improved the mechanical properties of the nanocomposite. The study also showed that the mechanical properties of the nanocomposite depended on the ultrasonic dispersion time. Long term dispersion damaged the surfaces of both untreated and plasma polymerized carbon nanofibers. The interface behavior and strengthening mechanisms are discussed.

Plasma deposition of thin carbonfluorine films on aligned carbon nanotube

The thin film of carbonfluorine was deposited on the surfaces of aligned carbon nanotubes using a plasma polymerization treatment. High-resolution transmission electron microscopy images revealed that a thin film of the polymer layer (20nm) was uniformly deposited on the surfaces of the aligned carbon nanotubes. Time-of-flight secondary ion mass spectroscopy and Fourier transform infrared experiments identified the carbonfluorine thin films on the carbon nanotubes. The plasma deposition mechanism is discussed.

プラズマ重合による有機薄膜合成とその機能化

Plasma polymerization and plasma treatment are useful methods for modifying the surface characteristics of organic materials. Plasma polymerization forms homogeneous organic thin films on material surfaces, and plasma treatment modifies chemically the surfaces of organic materials. These plasma processings give a hydrophilic or hydrophobic (water-repellent) property to the surfaces of materials

Plasma coating of carbon nanofibers for enhanced dispersion and interfacial bonding in polymer composites

Ultrathin films of polystyrene were deposited on the surfaces of carbon nanofibers using a plasma polymerization treatment. A small percent by weight of these surface-coated nanofibers were incorporated into polystyrene to form a polymer nanocomposite. The plasma coating greatly enhanced the dispersion of the nanofibers in the polymer matrix. High-resolution transmission-electron-microscopy (HRTEM) images revealed an extremely thin film of the polymer layer (∼3 nm) at the interface between the nanofiber and matrix. Tensile test results showed considerably increased strength in the coated nanofiber composite while an adverse effect was observed in the uncoated composites; the former exhibited shear yielding due to enhanced interfacial bonding while the latter fractured in a brittle fashion.

Plasma Coating and Enhanced Dispersion of Carbon Nanotubes

ABSTRACTUltrathin polymer films have been deposited on both multi-wall and aligned carbon nanotubes using a plasma polymerization treatment. TEM experimental results showed that a thin film of polystyrene layer (several nanometers) was uniformly deposited on the surfaces of the nanotubes including inner wall surfaces of the multi-wall nanotubes. The coated multi-wall nanotubes were mixed in polymer solutions for studying the effects of plasma coating on dispersion. It was found that the dispersion of multi-wall carbon nanotubes in polystyrene composite was significantly improved. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Plasma deposition of Ultrathin polymer films on carbon nanotubes

Ultrathin films of pyrrole were deposited on the surfaces of carbon nanotubes using a plasma polymerization treatment. High-resolution electron transmission microscopy images revealed that an extremely thin film of the polymer layer (2∼7 nm) was uniformly deposited on the outer and inner surfaces of the nanotubes. The nanotubes of all sizes exhibited equally uniform ultrathin films, indicating well-dispersed nanotubes in the fluidized bed reactor during the plasma treatment. In particular, the inner wall of the nanotube was also coated with a uniform ultrathin film of only ∼1–3 nm. Time-of-flight secondary ion mass spectroscopy experiments confirmed the highly branched and cross-linked polymer thin films on the carbon nanotubes. The plasma deposition mechanism is discussed in this letter.

Plasma deposition and characterization of acrylic acid thin film on ZnO nanoparticles

Acrylic acid polymer thin films were deposited on the surfaces of nanoparticles of ZnO using a plasma polymerization treatment. The average size of nanoparticles was on the order of 50 nm in irregular shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the acrylic acid layer (15 nm) was uniformly deposited on the surfaces of the nanoparticles. The HRTEM results were confirmed by time-of-flight secondary ion mass spectroscopy. The effect of plasma power on the polyacrylic thin film was studied by Fourier transform infrared experiments. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Interfacial Particle Bonding Via an Ultrathin Polymer Film on Al2O3 Nanoparticles by Plasma Polymerization

To study interfacial particle-to-particle bonding mechanisms, an ultrathin film of pyrrole was deposited on alumina nanoparticles using a plasma polymerization treatment. High resolution transmission electron microscopy experiments showed that an extremely thin film of the pyrrole layer (2 nm) was uniformly deposited on the surfaces of the nanoparticles. In particular, the particles of all sizes (10–150 nm) exhibited equally uniform ultrathin films indicating well-dispersed nanoparticles in the fluidized bed during the plasma treatment. Time-of-flight secondary ion mass spectroscopy experiments confirmed the nano-surface deposition of the pyrrole films on the nanoparticles. The pyrrole-coated nanoparticles were consolidated at a temperature range (approximately 250 °C) much lower than the conventional sintering temperature. The density of consolidated bulk alumina has reached about 95% of the theoretical density of alumina with only a few percent of polymer in the matrix. After low-temperature consolidation, the micro-hardness test was performed on the bulk samples to study the strength that was related to particle-particle adhesion. The underlying adhesion mechanism for bonding of the nanoparticles is discussed.

Coating of Ultrathin Polymer Films on Carbon Nanotubes by a Plasma Treatment

ABSTRACTUltrathin polymer films have been deposited on both single- and multi-wall carbon nanotubes using a plasma polymerization treatment. HRTEM experiments showed that an extremely thin film of the pyrrole layer (2–7 nm) was uniformly deposited on the surfaces of the nanotubes including inner wall surfaces of the multi-wall nanotubes. Time-of-Flight Secondary ion mass spectroscopy (TOFSIMS) experiments confirmed the nanosurface deposition of polymer thin films on the nanotubes. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Deposition of Polymer Thin Films on ZnO Nanoparticles by a Plasma Treatment

ABSTRACTUltrathin acrylic acid polymer films have been deposited on the surfaces of nanoparticles of ZnO using a plasma polymerization treatment. The average size of nanoparticles is on the order of 50 nm in irregular shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the acrylic acid layer (15 nm) was uniformly deposited on the surfaces of the nanoparticles. In particular, the particles of all sizes exhibited equally uniform ultrathin films indicating a well-dispersed nanoparticles in the fluidized bed during the plasma treatment. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Multi-Layer Coating of Ultrathin Polymer Films on Nanoparticles of Alumina by a Plasma Treatment

AbstractMulti-layer ultrathin polymer films have been deposited on the surfaces of nanoparticles of alumina using a plasma polymerization treatment. The nanoparticles ranged from 10-150 nm in spherical shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the pyrrole layer (10-20 Å) was uniformly deposited on the surfaces of the nanoparticles. In particular, the particles of all sizes (10-150 nm) exhibited equally uniform ultrathin films indicating well-dispersed nanoparticles in the fluidized bed during the plasma treatment. After single layer coating, hexamethyldisiloxane (HMDSO) was coated again as a second layer onto the surface of pyrrole. Subsequently, a third layer of pyrrole was coated on the top of HMDSO film completing the multi-layer coating process. Time-of-Flight Secondary ion mass spectroscopy (TOFSIMS) experiments confirmed the deposition of these multi-layer thin films on the nanoparticles. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

The competitive ablation and polymerization (CAP) principle and the plasma sensitivity of elements in plasma polymerization and treatment

The competitive ablation and polymerization (CAP) principle relates the ablation of materials in plasma to the deposition of materials in plasma. Plasma polymerization and plasma treatment cannot be elucidated without consideration of the fragmentation of molecules in both the gas and solid phases. The general fragmentation tendency follows a plasma sensitivity series of the elements involved that is based on element electronegativity. When consecutive plasma treatments, sequential plasma polymerization, or a combination of plasma treatment and plasma polymerization are carried out in the same reactor, factors that are often not considered in an ordinary individual process become crucial. The CAP principle and the concept of a plasma sensitivity series of the elements explain the rather complicated and interrelated influences of fragmented elements in the plasma deposition of materials. Plasma polymers should be considered a mixture of oligomers and polymeric networks. The oligomer content in a plasma-polymerized layer is vitally important to the adhesion of the plasma polymer to the substrate as well as to any subsequent coating applied to the layer of the plasma polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 943–953, 2000