Glow Discharge Plasma Polymerization Research Articles

Plasma Polymerized HMDSO Coatings For Syringes To Minimize Protein Adsorption.

Current parenteral containers used for the storage and delivery of protein-based drugs, contain silicone oil which may seep into the protein solution and can result in adsorption, aggregation and denaturation of the protein. Tightly adherent surface coatings prepared by radio frequency glow-discharge (RFGD) plasma polymerization are described in this paper. Using this robust technique, methacrylic acid (MA) (hydrophilic), hexamethyldisiloxane (HMDSO) (hydrophobic), tetraglyme (TG) (hydrophilic) were plasma polymerized onto glass. In addition, HMDSO and MA were copolymerized to create a plasma polymerized HMDSO-MA (hydrophobic) surface. Untreated glass and glass dip-coated in PDMS were used as controls. TG and MA plasma coatings adsorbed the least amount of protein in all pH conditions. Interestingly HMDSO-MA retained significantly lesser protein compared to HMDSO and dip-coated PDMS samples. In the presence of Polysorbate 80 (PS80) all plasma polymerized coatings adsorbed and retained negligible amounts of protein, compared to controls. Furthermore, the peak glide force of plasma coated syringes did not significantly increase compared to syringes without plasma coating. Due to the versatility of RFGD plasma, this process is scalable and could potentially be used for the treatment of hypodermic syringes used for the storage and delivery of protein-based therapeutics.

Tumble Polishing of Faster-Coated Glow Discharge Polymer Capsules

CH capsules fabricated by glow discharge plasma polymerization have been used as the capsule point design for the National Ignition Facility (NIF). The coating time ranges from 6 to 8 weeks. We have reduced the fabrication time by improving the coating rate. The faster coating rate results in an increased surface roughness in high-spatial-frequency modes >100. We employed the tumble finishing process developed for NIF capsules to improve the high mode roughness. Material properties such as surface finish, density, and relative oxygen uptake rate were examined for the faster-coated plastic. The reduction of glow discharge polymer (GDP) capsule production time without significant deviation from benchmarked capsule properties is discussed.

Towards improving mechanical properties of basalt fiber/polylactic acid composites by fiber surface treatments

Attempting to improve reinforcement effect on basalt fiber/polylactic acid composites, this study evaluates the effects of silane treatment, atmospheric glow discharge plasma polymerization, desizing, and addition of maleic anhydride coupling agent. The treated fibers were characterized, in terms of surface morphology and existing molecular bonds, and the mechanical properties of the composites were tested (i.e. strength, stiffness, and elongation at yield). Among the fiber surface treatments and the addition of coupling agent, improved mechanical properties were only shown by the silane treated and the atmospheric plasma polymerized composites by having 26 and 22% higher strength, respectively, as compared with the untreated one.

Changes in the optical properties of as-deposited plasma polymerized 2,6-diethylaniline thin films by iodine doping

In this study, plasma polymerized 2, 6-diethylaniline (PPDEA) thin films of different thicknesses were synthesized using a glow discharge plasma polymerization method. Scanning electron microscopy showed that the surface morphology of an as-deposited PPDEA thin film was comparatively smooth after iodine doping. The iodine-doped PPDEA was found to be thermally stable up to ca about 560K, which was slightly lower than that observed for as-deposited PPDEA. Ultraviolet-visible spectroscopic analyses demonstrated that iodine doping resulted in a significant decrease in the optical energy gap. As the doping period increased, the direct optical transition energy gap was reduced from 3.56 to 2.79eV and the indirect optical transition energy gap was decreased from 2.23 to 1.97eV. Thus it is observed that, the optical parameters of as-deposited PPDEA thin films with different thicknesses can be modified with different iodine doping periods.

Atmospheric pressure glow discharge plasma polymerization for surface treatment on sized basalt fiber/polylactic acid composites

This study evaluates the effects of atmospheric pressure glow discharge plasma polymerization on basalt fiber to the properties of basalt fiber/polylactic acid composite. Plasma exposure time was the object of interest so the basalt fiber was exposed to the glow for 0.5, 1.5, 3, 4.5, and 6min, respectively. Characterization was conducted on the plasma polymerized fibers by identifying the molecular bonds and surface morphology. Properties (mechanical and thermal) and water absorption behavior of the fabricated composites were tested. Plasma exposure time on BF affected mechanical properties of its BF/PLA composite, showing a decline in mechanical properties until the BF was plasma polymerized beyond 1.5min. Optimum plasma polymerization on BF was for 4.5min of plasma exposure time where the composite’s strength and modulus were 45% and 18% higher, respectively, compared to those of untreated one.

In vitro biocompatibility of plasma-aided surface-modified 316L stainless steel for intracoronary stents

316L-type stainless steel is a raw material mostly used for manufacturing metallic coronary stents. The purpose of this study was to examine the chemical, wettability, cytotoxic and haemocompatibility properties of 316L stainless steel stents which were modified by plasma polymerization. Six different polymeric compounds, polyethylene glycol, 2-hydroxyethyl methacrylate, ethylenediamine, acrylic acid, hexamethyldisilane and hexamethyldisiloxane, were used in a radio frequency glow discharge plasma polymerization system. As a model antiproliferative drug, mitomycin-C was chosen for covalent coupling onto the stent surface. Modified SS 316L stents were characterized by water contact angle measurements (goniometer) and x-ray photoelectron spectroscopy. C1s binding energies showed a good correlation with the literature. Haemocompatibility tests of coated SS 316L stents showed significant latency (t-test, p < 0.05) with respect to SS 316L and control groups in each test.

One-Step Method for Generating PEG-Like Plasma Polymer Gradients: Chemical Characterization and Analysis of Protein Interactions

In this work we report a one-step method for the fabrication of poly(ethylene glycol) PEG-like chemical gradients, which were deposited via continuous wave radio frequency glow discharge plasma polymerization of diethylene glycol dimethyl ether (DG). A knife edge top electrode was used to produce the gradient coatings at plasma load powers of 5 and 30 W. The chemistry across the gradients was analyzed using a number of complementary techniques including spatially resolved synchrotron source grazing incidence FTIR microspectroscopy, X-ray photoelectron spectroscopy (XPS) and synchrotron source near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Gradients deposited at lower load power retained a higher degree of monomer like functionality as did the central region directly underneath the knife edge electrode of each gradient film. Surface derivatization experiments were employed to investigate the concentration of residual ether units in the films. In addition, surface derivatization was used to investigate the reactivity of the gradient films toward primary amine groups in a graft copolymer of poly (L-lysine) and poly(ethylene glycol) (PLL-g-PEG copolymer) which was correlated to residual aldehyde, ketone and carboxylic acid functionalities within the films. The protein adsorption characteristics of the gradients were analyzed using three proteins of varying size and charge. Protein adsorption varied and was dependent on the chemistry and the physical properties (such as size and charge) of the proteins. A correlation between the concentration of ether functionality and the protein fouling characteristics along the gradient films was observed. The gradient coating technique developed in this work allows for the efficient and high-throughput study of biomaterial gradient coating interactions.

Plasma polymer thin film depositions to regulate gas permeability through nanoporous track etched membranes

Deposition of thin polymeric films on nanoporous membranes is shown to provide a mechanically simple and inexpensive approach to regulate trans-membrane gas flows. For this purpose, polymeric films were deposited on polycarbonate track-etched (PCTE) membranes of 50 nm and 100 nm pore size. The films were generated by low-pressure glow discharge plasma polymerization of vinyl acetic acid (CH 2 CHCH 2COOH) or perfluorohexane ( n-C 6F 14) monomers. The plasma discharge was operated under pulsed conditions to provide better control of the polymeric film chemistry along with improved control of film thickness. The gradual reduction in average membrane pore sizes with increasing film thickness resulted in controlled decreases in the permeation rates of O 2 and CO 2 gases. In addition to film thickness, the permeation rates were observed to be functions of the specific composition and cross-link density of the polymer films deposited, as well as the nature of the permeant gases. It was determined that the plasma deposition process employed provides sufficient permeation control for use in applications requiring fine modulation of gas permeation rate such as those encountered in development of a blood oxygenator, a major motivation for the present study.

Surface chemistry influences implant‐mediated host tissue responses

Implant-mediated fibrotic reactions are detrimental to the performance of encapsulated cells, implanted drug release devices, and sensors. To improve the implant function and longevity, recent research has emphasized the need for inducing alterations in cellular responses. Although material surface functional groups have been shown to be potent in affecting cellular activity in vitro and short-term in vivo responses, these groups appear to have little influence on long-term in vivo fibrotic reactions, possibly as a result of insufficient interactions between recruited host cells and functional groups on the implants. To maximize the influence of functionality on cells, and to mimic drug release microspheres, functionalized micron-sized particles were created and tested for their ability in modulating tissue responses to biomaterial implants. In this work, the surfaces of polypropylene particles were controllably coated with four different functional groups, specifically -OH, -NH(2), -CF(x), and -COOH, using a radio frequency glow discharge plasma polymerization technique. The effect of these surface functionalities on host tissue responses were then evaluated using a mice subcutaneous implantation model. Major differences were observed in contrasting tissue response to the different chemistries. Surfaces with -OH and -NH(2) surface groups induced the thickest fibrous capsule accompanied with the greatest cellular infiltration into the implants. In contrast, surfaces with -CF(x) and -COOH exhibited the least inflammatory/fibrotic responses and cellular infiltrations. The present results clearly demonstrate that, by increasing the available functionalized surface area and spatial distribution, the effect of surface chemistry on tissue reactivity can be substantially enhanced.

Modification of a Nafion® ion exchange membrane by a plasma polymerization process

Abstract An ultra-thin anionic exchange layer was deposited on the surface of a Nafion® membrane. This layer was deposited from ethylene and ammonia using a glow–discharge plasma polymerization technique. The scanning electron microscopy (SEM), Fourier transform infrared attenuated total reflection (FTIR-ATR) spectra and X-ray photoelectron spectroscopy (XPS) showed that the resulting plasma film containing amine and amide was about 0.5 μm thick. The ion selectivity coefficient for H+ of the plasma modified Nafion® membrane was measured and the results showed that a linear Nernst response was exhibited and the selectivity of proton was enhanced. The resistance of modified Nafion® was only slightly higher than that of the Nafion® membrane.

Preparation of Thin Cation‐Exchange Membranes Using Glow Discharge Plasma Polymerization and Its Reactions

Thin cation‐exchange films with fixed sulfonic acid groups were prepared by plasma polymerization followed by hydrolysis of sulfonyl halide groups using benzenesulfonyl fluoride and benzenesulfonyl chloride as starting materials. For benzenesulfonyl fluoride, sulfonyl fluoride groups were introduced into the plasma‐formed polymers, whereas benzenesulfonyl chloride tended to decompose during plasma polymerization. The difference between the reaction in the glow discharge plasma of benzenesulfonyl fluoride and that of benzenesulfonyl chloride is discussed based on results obtained by in situ mass spectrometry and molecular orbital calculations. For benzenesulfonyl fluoride, the parent ion is the major species which introduces the sulfonic fluoride groups into the plasma polymer because S‒F bond cleavage is difficult. However, the parent ion of benzenesulfonyl chloride is unstable in the glow discharge plasma, and cleavage of the S‒Cl bond is facile and produces Cl radicals. The plasma polymer formed at 3.5 W using benzenesulfonyl fluoride exhibits a cation‐exchange capacity of after hydrolysis, which is comparable to the capacities of commercially available cation‐exchange membranes. © 2000 The Electrochemical Society. All rights reserved.

Fibrinogen adsorption and host tissue responses to plasma functionalized surfaces.

The physical and chemical characteristics of material surfaces are thought to play important roles in biomaterial-mediated tissue responses. To understand the importance of discrete biomaterial chemical characteristics in modifying host tissue responses, we constructed surfaces bearing different functional groups using radio frequency glow discharge plasma polymerization. Surfaces evaluated included those having high concentrations of -OH, -NH2, -CF3, and siloxyl groups. These surfaces and polyethylene terephthalate controls were used to assess the importance of particular physicochemical characteristics in surface:protein:cell interactions both in vitro and in vivo. The results obtained show that surface functionalities do significantly affect both the adsorption and "denaturation" of adsorbed fibrinogen (which is an important mediator of inflammatory responses to biomaterial implants). In addition, these surfaces provoke different degrees of acute inflammatory responses. Interestingly, the amounts of "denatured" fibrinogen that spontaneously accumulate on the individual surfaces correlate closely with the extent of biomaterial-mediated inflammation. These results suggest that surfaces that tend to "irreversibly" bind fibrinogen prompt greater acute inflammatory responses. Unexpectedly, all test surfaces except those bearing a siloxyl group engender relatively similar biomaterial-mediated fibrotic responses. Thus surface functionalities alone may not be sufficient to affect subsequent fibrotic responses.

The chemiluminescence response of neutrophils on polymer surfaces made by glow discharge plasma polymerization.

Polypropylene tubes were coated with different polymers made by glow discharge plasma polymerization. Isolated human blood neutrophils were allowed to interact with the polymer surface and the chemiluminescence response of the cells was recorded as a measure of oxidative activation. The polymers represented surfaces that differed markedly with respect to charge, hardness, and wettability. We found that all polymers stimulated the chemiluminescence response in neutrophils differently; when preincubation with human serum albumin (HSA) there was a general reduction of the chemiluminescence response particularly on one of the positively charged surface 1,2-diamino-cyclohexane (DACH). Addition of a soluble stimulus, the chemoattractant formylmethionyl-leucylphenylalanine (FMLP), to the cells caused a dramatic increase in the response on one of the hydrophobic surface hexamethylene-disiloxane (HMDSO). However, there was also a pronounced reduction in the response on polymers with acrylic acid (AA). The response was normalized after addition of HSA. Taken together, the chemiluminescence response of the neutrophils interacting with the polymer surfaces differed with regard to the type of surfaces. When HSA and FMLP were added a larger difference in the response was found. Our results showed that the activation of human neutrophil granulocytes influenced by different polymer surfaces, followed unspecific different patterns which were someway related to the specific characteristics of the polymer and from this point we came to similar conclusions made by Kaplan et al. (J. Biomater. Res. 28, 377 (1994)), that it is difficult to extrapolate any activation mechanisms from one material to another.(ABSTRACT TRUNCATED AT 250 WORDS)

A hydrophilic plasma polymerized film composite with potential application as an interface for biomaterials

A hydrophilic polymer composite film (approx. 420 nm thick), with potential application as an interface for biomaterials has been prepared on nonorganic substrates, which include glass, silicon, and aluminum foil, using a glow discharge plasma polymerization technique. A thin film (110 nm thick) polymerized from hexane provided an adherent protective coating for the substrate material, and covalent bonding sites for the outer layer polymerized from N-vinyl-2-pyrrolidone. This outer layer provided the hydrophilic surface or interface. The two layers were copolymerized for a short period during transition between monomers to provide an intimate covalently bonded diffuse interphase. Preliminary in vitro and in vivo biocompatibility studies indicate that the hydrophilic film is non-cytotoxic, and does not increase the inflammatory response when compared with negative controls.

Ionically Conductive Thin Polymer Film Prepared by Plasma Polymerization: I . Hybrid Film of Plasma Polymer Formed from Octamethylcyclotetrasiloxane, Poly(propylene oxide), and Lithium Perchlorate

Ultrathin polymer membranes are prepared by polymerizing octamethylcyclotetrasiloxane in glow discharge. Membranes formed by glow discharge (plasma) polymerization are uniform and pinhole‐free. Polymeric solid electrolyte membranes are prepared by hybridization of plasma polymer formed from octamethylcyclotetrasiloxane, poly(propylene oxide), and lithium perchlorate. The films are about 1 μm thick and show high ionic conductivity of the order of 10−6S · cm−1 (10 Ω cm2 resistance per unit area of solid polymer electrolyte) at 60°C. The conductivity depends on the content of lithium perchlorate, and its temperature dependence fits with the WLF‐type equation rather than the Arrhenius equation.

Preparation and electrical properties of plasma- polymerized copper acetylacetonate thin films

Thin films of polymeric copper acetylacetonate were prepared by means of glow discharge plasma polymerization. The films thus obtained showed a variety of colours such as colourless transparent, yellow, green, blue, red and gold as well as a wide range of electroconductivities from insulating (10 -10 S cm -1 or less) to metallic (10 4 S cm -1 or more) depending on the plasma conditions. With increasing total plasma energy, e.g. by increasing the plasma power, and/or the plasma duration, the film became more conductive. The films with a conductivity between 10 -5 and 10 -2 S cm -1 showed bistable switching characteristics corresponding to high resistance (OFF) and low resistance (ON) states. The structure of the films was investigated using Fourier transform IR spectroscopy, X-ray photoelectron spectroscopy, electron diffraction and electron microscopy, and a texture of dispersed metal islands within the polymer matrix was found.

Preparation and electrical properties of polymeric copper phthalocyanine thin films by plasma polymerization

Polymeric copper phthalocyanine (CuPc) thin films (600–3000 Å thick) were prepared for the first time by glow-discharge plasma polymerization. The film largely maintained the original structure of CuPc. The films obtained were interposed between aluminum and ITO electrodes (Al/polymeric CuPc/ITO) and the electrical properties of the sandwich cells have been studied. These cells were found to exhibit good rectification, photovoltaic, photoreduction, and electrochromic characteristics.

The rate of adhesion of melanoma cells onto nonionic polymer surfaces

The rates of adhesion of melanoma cells (carcinogenic) onto nonionic polymer surfaces were studied by using radioactively labeled cells and measuring the fraction of cells which adhered to the surface in a given time. Glow discharge (plasma) polymerization of 1,1,3,3-tetramethyldisiloxane and of nitrogen-acetylene-water (mole ratio 0.4:1.0:0.2) was used to modify the surface energy of the substrate. The cell adhesion rate was found to be given by Y = 1 - exp [-k0(gammas - gamma0)t], where Y is the fraction of cells adhered, -k0 is a characteristic rate constant, gammas is the total surface energy of the substrate, gamma0 is the threshold surface energy of cell adhesion, and t is time.

Some aspects of plasma polymerization investigated by pulsed R.F. discharge

AbstractThe polymerization of organic compounds in glow discharge (plasma polymerization) was investigated by using pulsed R.F. discharge (100 μsec on, 900 μsec off). The effects of pulsed discharge on polymer deposition rate, pressure change in plasma, ESR signals of free spins in both plasma polymer and substrate, and the contact angle of water on the plasma polymer surface were investigated for various organic compounds. The results are correlated to the mechanisms of polymer formation in plasma (plasma polymerization) which has been postulated as repeating processes of stepwise (propagation) reactions. The effect of the pulse is different from one group of organic compounds to another depending on whether or not they contain an olefinic double bond and/or a triple bond. The main difference seems to be the addition polymerization which can occur exclusively during the off‐period of pulsed discharge. Ultraviolet emission from pulsed discharge is much less than from continuous discharge. Consequently, the fragmentation of the monomer and the free‐radical formation in the substrate are less with the pulsed discharge. Properties of polymers from some organic compounds formed in continuous and in pulsed discharge were found to be significantly different, and the differences were postulated from the changes of polymerization mechanisms in the pulsed discharge.