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Comparison of argon plasma-induced surface changes of thermoplastic polymers

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Comparison of argon plasma-induced surface changes of thermoplastic polymers

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Abstract

Modification of high-density polyethylene (PE), polytetrafluoroethylene (PTFE), polystyrene (PS), polyethyleneterephthalate (PET) and polypropylene (PP) by Ar plasma was studied. The amount of the ablated material was determined by gravimetry. Wettability of polymers after the plasma treatment was determined from the contact angle measurement. The changes in the surface morphology of polymers were observed using atomic force microscopy (AFM). Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Surface changes were also studied by the determination of electrokinetic potential (ζ-potential). It was found that under the plasma treatment the polymers are ablated and their surface morphology and roughness are changed dramatically. XPS measurements indicate an oxidation of the polymer surface. The plasma treatment results in a dramatic increase of the ζ-potential. EPR data show different radical amount present on the treated surface of all polymers. Most significant changes due to the degradation of polymer chains are observed on PTFE.

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... As a result of plasma activation, the surface topography changes and surface roughness is usually observed to increase significantly [40,57,75,80], although sometimes there may also be a slight decrease [81]. In addition, it has been observed that the increase in activation time and power increase leads to further increases in roughness [10,14,19,46,59,78]. ...
... The influence of exposure time on wettability and, thus, the improvement of plastic printing capacity depends, among other things, on the type of activated material and plasma type used.Řezníčková et al. [81] observed a greater effect of activation time on the change of water contact angle with PTFE than HDPE, PS, PET, and PP. Regardless of the activation time and type of material, however, they found that plasma activation with Ar had a beneficial effect on the wettability of all materials, significantly lowering the contact angle even when using the shortest duration of activation. ...
... However, numerous studies have reported that the increase in activation time has further improved wettability [19,34,46,77,81]. Vesel et al. [34], using low pressure oxygen and nitrogen plasma on PET, observed a beneficial effect of the activation time extension on the wettability of the material (further reduction of contact angle). ...
Chapter
This chapter describes an application of plasma in printed substrates and the influence of plasma treatment on polymers and polymeric composites, their printability and prints quality. Plasma is one of physical methods of surface modification that includes among others corona, flame and laser treatment. Contrary to the corona treatment, plasma activation enables very uniform modification. Due to attributes of polymers, their thermal sensitivity, their modification is almost exclusively done using cold plasma, described in depth in this chapter. Additionally, the changes induced in the material are explained. Especially substrate wettability and its roughness are of paramount importance, impacting significantly printability. Moreover, the influence of selected parameters of plasma treatment on surface modification is presented. Due to the fact, that changes induced in the material surface are not permanent, the chapter goes also into more detail about aging process in relation to the type of polymer, conditions of plasma activation and storage.
... The prepared samples were stored at laboratory conditions. More detailed description of the plasma treatment and gold deposition techniques can be found in [12,13]. ...
... In the plasma treated samples, the carbon content decreased from 88.8 at.% (pristine PEEK) to 60.1 at.% (PEEK 240 s). This was probably caused by an ablation of the surface layer [12]. Conversely, concentration of gold increases with the formation of a thicker gold layer. ...
... As reported in bibliography also for other kinds of substrates, the wettability increase is caused by creation of polar groups, exhibiting enhanced hydrophilicity, on the polymer surface [34] and by the surface roughness modification [35]. This is related to the contact angle, which is mostly affected by the chemical structure and morphology of the polymer surface layer, especially by the presence of oxidized degradation products [34,36] and by the texturing of the surface [35]. ...
... As reported in bibliography also for other kinds of substrates, the wettability increase is caused by creation of polar groups, exhibiting enhanced hydrophilicity, on the polymer surface [34] and by the surface roughness modification [35]. This is related to the contact angle, which is mostly affected by the chemical structure and morphology of the polymer surface layer, especially by the presence of oxidized degradation products [34,36] and by the texturing of the surface [35]. ...
Article
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... Thus, in the present work, the highest hydrophilicity values are those for O 2 discharge. In addition, once the discharge ends, C• on the surface can react with atmospheric O 2 [30], and when removed from the reaction chamber, they oxidize the material and increase the presence of (C=O), (C=O-OH), esters (C=O-O-R) and (-OH) [14,37]. . Letters correspond to heterogeneous groups obtained by Tukey post hoc test, where letter a corresponds to the best treatment, followed by letters ab and bc. ...
... Thus, in the present work, the highest hydrophilicity values are those for O2 discharge. In addition, once the discharge ends, C• on the surface can react with atmospheric O2 [30], and when removed from the reaction chamber, they oxidize the material and increase the presence of (C=O), (C=O-OH), esters (C=O-O-R) and (-OH) [14,37] Abou Rich et al. [30] describe LDPE exposed to the environment after plasma discharge generates O• and hydroxyl radicals (OH•) that tend to take secondary hydrogens from the LDPE chains, resulting in the formation of alkyl radicals (CH3•) [30]. These radicals can react with atomic oxygen (O2) or ozone (O3), allowing the formation of alkoxy (C-O•). ...
Article
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... Ti surfaces were preactivated in the oxygen-plasma reactor, then were polymerized with allylamine film. The surface charges of this modified Ti surfaces were verified with zeta potential using the solution of 0.001 M KCI (see Fig. 16), showing increased positive potential up to 9 mV over the plasma-treated Ti surfaces [235][236][237]. This amino-functionalized Ti surfaces showed increased cellular adhesion and spreading, even better than control surface coated with the ECM protein collagen and not modified Ti. ...
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... Furthermore, the water contact angles were further reduced at 80 W when compared to 10 and 50 W, down to 29.4° ± 3.0 and 15.2° ± 4.0 for 1 and 30 min of duration respectively. The hydrophilicity increase detected by the reduced water contact angles can be attributed to chemical reconfigurations with polar species as previously discussed within the XPS and streaming potential sections 55 . However, the hydrophilicity enhancement promoted by plasma treatment, showed to be influenced by smooth surfaces 56 . ...
Article
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... In many cases, after modification with aim to increase the surface free energy this process is explained by the formation of new functional groups on a surface (-OH, -COOH, etc.). A characteristic feature of this method is that it influences the polymer surface to a small depth (up to 10 nm), and so the bulk of the polymer and its bulk properties (toughness, strength) remain unchanged [15,16]. ...
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... Plasma treatment does not produce toxic waste in contrast to the treatments using chemicals. The plasma is capable to exert four major effects (Chen, 2001;Reznickova et al., 2011) surface cleaning, surface ablation or etching, surface cross-linking, and modification of the surface chemical structure, occurring both in situ or after subsequent exposure to the atmosphere. These effects depend on a presence of the active species in plasma (electrons, ions, radicals, photons) which interact with polymer surfaces and modify their chemical and physical properties. ...
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... The rise of oxygen concentration is generated by newly created polar oxygen groups, such as, carbonyl, carboxyl and hydroxyl. 31 The morphological changes of the PEEK surface induced by the Ar plasma treatment were assessed by AFM method. Fig. 1 illustrates a dramatic change in morphology of the PEEK surface before and aer plasma treatment for varying treatment times (0-480 s). ...
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Despite the extensive use of polyetheretherketone (PEEK) in biomedical applications, information about cell adhesion on this biomaterial is limited. This study focuses on PEEK tuned by argon plasma treatment with the aim to enhance its wettability and cytocompatibility. Changes in surface properties of the plasma treated surface were studied in relation to the adhesion, proliferation and metabolic activity of mouse fibroblasts (L929) and human osteoblast (U-2 OS) in vitro. Moreover, the expression profiles of two proteins (talin 1 and vinculin) responsible for cell adhesion, were determined at 2 time points in dependence on the PEEK treatment. Plasma treatment increased the surface wettability of PEEK and led to changes in its surface morphology and chemistry. The XPS method showed a decrease in carbon content and augmentation of oxygen concentration with increasing effect of the plasma. Plasma treatment of PEEK significantly enhanced cell adhesion, proliferation and metabolic activity of both cell lines when compared to pristine PEEK. Moreover, special attention was devoted to filopodia of L929 cell adhered on PEEK studied by means of scanning electron microscopy. The most abundant filopodia were present on PEEK plasma treated for “longer” times.
... By applying these principals, polymer materials treated with plasma can be drastically altered in terms of their chemical structure and surface properties. In addition, plasma treatment (Fig. 6) is a simple, effective, and versatile technique for stabilization or surface treatment in the plasma zone [15,[118][119][120][121]. ...
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The process of oxidizing polyacrylonitrile (PAN)-based carbon fibers converts them into an infusible and non-flammable state prior to carbonization. This represents one of the most important stages in determining the mechanical properties of the final carbon fibers, but the most commonly used methods, such as thermal treatment (200°C to 300°C), tend to waste a great deal of process time, money, and energy. There is therefore a need to develop more advanced oxidation methods for PAN precursor fibers. In this review, we assess the viability of electron beam, gamma-ray, ultra-violet, and plasma treatments with a view to advancing these areas of research and their industrial application.
... Layer-by-layer selfassembly of NPs has also been demonstrated, but this method could be sensitive to environmental conditions [29,30]. Surface modification techniques that allows covalent attachment of NPs to surfaces, such as plasma treatment, have been explored, but this approach usually requires several post-processing steps after plasma activation of the surface in order to attach NPs [31][32][33]. ...
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... 27.5% (after 240 s). The rise of oxygen concentration is generated by newly created polar oxygen groups, such as, carbonyl, carboxyl, and hydroxyl [42]. The sample surface after 240 s of plasma treatment was ablated and disrupted to larger extent than that of 60 s, therefore the oxygen concentration was higher for samples treated by plasma for longer periods. ...
Article
We have investigated the application of Ar plasma for creation of nanostructured ultra high molecular weight polyethylene (PE) surface in order to enhance adhesion of mouse embryonic fibroblasts (L929). The aim of this study was to investigate the effect of the interface between plasma-treated and gold-coated PE on adhesion and spreading of cells. The surface properties of pristine samples and its modified counterparts were studied by different experimental techniques (gravimetry, goniometry and X-ray photoelectron spectroscopy (XPS), electrokinetic analysis), which were used for characterization of treated and sputtered layers, polarity and surface chemical structure, respectively. Further, atomic force microscopy (AFM) was employed to study the surface morphology and roughness. Biological responses of cells seeded on PE samples were evaluated in terms of cell adhesion, spreading, morphology and proliferation. Detailed cell morphology and intercellular connections were followed by scanning electron microscopy (SEM). As it was expected the thickness of a deposited gold film was an increasing function of the sputtering time. Despite the fact that plasma treatment proceeded in inert plasma, oxidized degradation products were formed on the PE surface which would contribute to increased hydrophilicity (wettability) of the plasma treated polymer. The XPS method showed a decrease in carbon concentration with increasing plasma treatment. Cell adhesion measured on the interface between plasma treated and gold coated PE was inversely proportional to the thickness of a gold layer on a sample.
... Different types of biomaterials may be used, i.e. simple polyolefins (Kasálková et al., 2010;Slepička et al., 2012a;Řezníčková et al., 2011), biodegradable polymers (Novák et al., 2012;Synytsya et al., 2009Synytsya et al., , 2012 or materials based on special additional treatments (Grausova et al., 2009;Vandrovcova et al., 2008;Pařízek et al., 2013). ...
... Rezinckova et al. studied surface modification of polyethylene (PE), PTFE, PS, PET and PP treated by Ar plasma. They inferred that under the plasma treatment, the polymers are ablated and their surface morphology and roughness were changed dramatically [51]. Khorasan et al. used radio frequency (RF) plasma treatment in which O 2 was applied to modify the surface of poly (L-lactic acid) (PLLA) and poly (d, I-lactic acid-coglycolic acid) (PLGA). ...
Article
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... The surface morphology of treating polymers was affected by the plasma power, exposure time, and type of working gas [148]- [150]. In terms of surface morphology, carbonyl, carboxyl, and hydroxyl are the possible polar groups introduced in the outermost layers of the surface by reactions with plasma species. ...
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... The samples were treated in Ar + plasma on a Balzers SCD 050 device: the exposure time was 120 s, and the discharge power was 8.3 W. The plasma treatment was accomplished at room temperature. More detailed description of the plasma modification can be found in [13]. ...
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Selected polymers (polyethylene-PE, polypropylene-PP, polytetrafluoroethylene-PTFE, polystyrene-PS and polyethylenterephthalate-PET) were irradiated with the linearly polarized light of a pulsed 157 nm F2 laser. The irradiation results in degradation of polymers and ablation of polymer surfaces. Contact angle, measured by goniometry, was studied as a function of the number of laser pulses. The volume of the ablated polymer layer was determined by gravimetry. Changes in surface morphology and roughness were observed using atomic force microscopy. Surface chemistry of the samples was investigated by electrokinetic analysis and by XPS. While PET and PE exhibit small ablation, the ablation of PS and PTFE is more significant, and the most pronounced ablation is observed on PP. Contact angle of all polymers, with the only exception of PP, is a decreasing function of the number of laser pulses up to 2000 pulses. Laser irradiation leads to a refinement of the polymer surface morphology and a decrease of their surface roughness. Electrokinetic analysis and PS show changes in the surface chemistry of polymers after the laser treatment. Copyright © 2011 John Wiley & Sons, Ltd.
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This paper is focused on characterization of surface properties of PMP (poly-4-methyl-1-pentene) after the modification of its upper layer. PMP is a thermoplastic polyolefine, which is used e.g. in medicine for its mechanical and thermal stability, for medical and laboratory equipment. Modification was carried out by Ar plasma, KrF excimer laser beam, thermal annealing and their combinations. The changes in physico-chemical properties of surface layer, such as wettability, ablation, morphology, roughness and chemical composition, were determined. Finally, the tests of adhesion and proliferation of cells were carried out on the selected samples. PMP seems a very resistant material, but plasma exposure can affect its surface properties, e.g. wettability or atomic concentrations of elements, which cause improvement of VSMC cells ability to adhere and proliferate. All used methods have just minor effect on morphology. Except under extreme conditions, a KrF excimer laser beam has only insignificant influence on PMP changes. Because of that, PMP could be suitable as a resistant carrier for materials for the further laser modification.
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Electrokinetic potential (zeta potential) is a characteristic parameter for description of the surface chemistry of solid flat materials and it can be used for a fast analysis of materials modified by different chemical or physical methods. Due to its sensitivity, zeta potential is able to distinguish surface modified by coating with monolayers of various materials or nanostructures created after plasma treatment. Also metal nanostructures deposited on surfaces can be characterized by zeta potential. It can also be used for isoelectric point determination of materials. We present data on zeta potential in 0.001 mol/dm3 KCl at constant pH7.0 and also in pH range (2.5-7.0) for isoelectric point determination for pristine polymers PET, PTFE, PS, LDPE, HDPE, PLLA, PVF, PVDF, PMP and polyimides (Upilex R, Upilex S, Kapton). The zeta potential of selected polymers, modified by plasma and by chemical coatings (e.g. by biphenyldithiol or polyethyleneglycol) or by gold deposition was measured too. Zeta potentials of these modified materials were also studied to confirmation that electrokinetic analysis is acceptable method for their fast description.
Article
High-value recycling petroleum-based polyethylene (PE) can effectively reduce carbon emissions and promote a circular economy. This study proposed a new method for functionalisation of low density polyethylene (LDPE) matrix at gas-liquid interface. The controlled functionalisation of LDPE at molten state was successfully achieved using ozone by altering reaction parameters. After ozone treatment, functionalised groups such as ketone (C=O), ether (C-O-C) and carboxyl groups (-COOH) were generated in ozonized PE (OPE) confirmed by FTIR and XPS. The contact angle with water dropped from 99 º of pristine PE to 85.4 º of OPE, which demonstrated that the hydrophilicity of OPE was improved significantly. The degree of ozonation was sensitive to temperature. A slight degradation of PE predominantly occurred under the mild condition (below 220 ℃ within 2 h) while the cross-linking structure was primarily generated after further oxidation (beyond 240 ℃ over 4 h), which revealed that functionalisation of OPE could be controllably achieved. Due to the formation of cross-linking structure, the crystallinity of OPE decreased from 33.8 % to 11.0 %. Meanwhile, the residue weight of OPE had a slight increase while its activation energy of thermal degradation reduced. Therefore, the functionalisation of PE using ozone is a promising technical and environmental-friendly approach to upcycle PE in the future.
Article
This study focuses on high density polyethylene (HDPE) activated by Ar plasma treatment, subsequently grafted with copper sulfonated phthalocyanine (CuPc) especially pointing out to the surface and magnetic properties of those composites. Properties of pristine PE and their plasma treated counterparts were studied by different experimental techniques: X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, zeta potential and by electron spin resonance (ESR). XPS analysis confirmed the successful grafting of phthalocyanine. The highest absorption was found for the sample grafted with bCuPc for 1 h. Electrokinetic analysis also confirmed the plasma treatment and also subsequent CuPc grafting influence significantly the surface chemistry and charge. These results correspond well with XPS determination. ESR studies confirmed the presence of CuPc grafted on HDPE. It was found, that grafting is mediated by magnetically inactive functional groups, rather than radicals. Magnetic properties of CuPc do not seem to change significantly after grafting CuPc on polyethylene surface.
Article
The modification of polymer surfaces with fluorine–oxygen mixtures has been studied with wide variations in the process duration and percentage ratio between these gases in the mixture. The modification increases the hydrophilicity of the polymer surface, and, the higher the fraction of oxygen in the gas mixture and the longer the oxyfluorination time, the greater the increase in the hydrophilicity. The physicochemical properties of polymers, such as wettability, surface energy, and adhesion, may be regulated within rather wide ranges by varying oxyfluorination conditions. For example, in the case of polyolefins, the water contact angle changes from 78°‒87° for initial polymers to 49°‒60° for modified ones. For heterochain polymers, this range may be even wider and is for, e.g., poly(ethylene terephthalate) from 67° to 4°; i.e. almost complete water spreading over the polymer surface is achieved. The contribution of the polymer surface roughness to the observed values of the water contact angle has been determined before and after the chemical treatment. It has been shown that an increase in the wettability of the polymer surface as a result of oxyfluorination may be used to obtain polymer films capable of altering their wettability under subsequent tensile deformation.
Article
Octenidine dihydrochloride (OCT) has a wide spectrum of antibacterial, antifungal and virucidal activity. OCT is also newly used in tissue engineering. The aim of this work was to create a new nanocomposite consisting of OCT‐grafted polymer with (i) antibacterial effect and/or (ii) surface for better cell adhesion and proliferation. The polymer foils were chemically activated with Piranha solution and subsequently grafted with OCT. Changes in surface properties before and after modifications were detected by electrokinetic analysis, goniometry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The final nanocomposite polymer/OCT exhibits antibacterial activity against Staphylococcus epidermidis (S. epidermidis). The new nanocomposite material has also been shown to support the growth of B14 cell culture on the substrate and to form cell multilayers, which could lead to the formation of spheroids. This behaviour strongly depends on the concentration of OCT grafted onto the polymer surfaces. This new nanocomposite could be used in medicine, for bioapplications, environmental protection.
Article
Polymeric biomaterials play an important role in medicine as catheters, stents, vascular grafts, or artificial heart valves. For example, PTFE has superb thermal stability, low dielectric constant, dissipation factor, excellent chemical inertness and exceptionally low frictional coefficient. However, its applicability is hampered in many cases due to its poor wettability and adhesion to other materials. In our study, we present simple technique of altering surface properties of PTFE by plasma treatment at increased temperature (from 37 °C – body temperature to 121 °C – temperature of sterilization). We have studied the effect of the modification process parameters on surface properties and biological response of the material. For biological tests we have selected vascular smooth muscle cells (VSMC) as a model line for application of our samples for applications where rapid cell growth is undesirable, such as artificial heart valves. The results have shown that proliferation of VSMC on plasma treated PTFE for 480 s at 121 °C is significantly lower compared to standard of tissue culture polystyrene (TCPS). Based on this result the risk of negative response of biological system such as inflammation, immune reactions and coalescence of VSMC in heart valve is minimized.
Article
A low power low frequency (50 Hz) argon plasma was used to treat the surface of polystyrene (PS) films. Plasma treatment for 3 min produced the best hydrophilic enhancement and it corresponded to doubling of the surface energy. At 45 Pa and flowrate of 44 sccm, a ‘saturation’ region in terms of lowest water contact angle (WCA) attained (WCA = 21°±3°), occurred at low discharge power of 0.15-0.25 W (applied power of 3-8 W). The induced hydrophilicity was attributed mainly to the oxygen-containing functional groups incorporated on the PS surface during the plasma treatment. Oxygen was speculated to be sourced from the dissociation of residual water vapour in the reactor chamber. Upon exposure to the laboratory environment, rapid hydrophobic recovery of the treated samples occurred but WCA stabilized after 72 h and remained at more than 30° below its value at pristine condition.
Chapter
Polyolefins are well-known and the most commonly used polymers worldwide. Advantages like outstanding mechanical properties, chemical resistance, low cost, and processability are neighboring with some drawbacks like relatively high gas and vapor permeability, low surface energy. This chapter introduces surface plasma modification as an environmentally friendly, fast, and versatile technique. Details regarding different plasma reactor designs, generation methods, working parameters suitable for treating polyolefins are presented. Furthermore, plasma activation, grafting, and etching are described as the most commonly used techniques for surface energy modification to enhance polyolefins' biocompatibility, printability, adhesion to materials, and other parameters. For instance, plasma activation cross-linking of the polymer chains can be achieved, which leads to gas and vapor permeability improvement. Choice of working conditions allows controlling the degree of cross-linking, the type, and the concentration of the incorporated functional groups on the surface. Plasma polymerization is introduced as a technique for coating deposition with different properties and functionality depending on the operating parameters and monomer selection. Improvement of barrier layer performance and modification of the surface energy are the main applications of plasma polymerization of polyolefins.
Chapter
Polypropylene membrane with the base of polyolefin exhibits promising applications such as packaging, medical tools, and especially in the filtration industry, due to its outstanding properties such as well mechanical features, recyclability, acceptable resistance to temperature and chemicals, and reasonable price. However, its applications are restricted by its hydrophobic nature. To amend the surface physical and chemical properties of polypropylene and broaden its usage, well-known methodologies such as laser modification and plasma irradiation have been investigated more than the other methods. Herein, in this chapter, the investigations on the surface refinement of polypropylene using laser and plasma are discussed. Furthermore, a comparison between the effectiveness of both methods (i.e. laser modification and plasma irradiation) is presented.
Article
Plasma surface treatment has a wide range of applications in biomedicine. In the present study, flat polylactic acid (PLA) films were treated with oxygen and nitrogen, low-pressure, non-thermal plasma. The water contact angle of the PLA films dramatically decreased from 67° in the untreated surface to 34° and 38° in surfaces treated with nitrogen and oxygen plasma, respectively. Conversely, after the plasma treatment, the surface free energy of the films increased considerably from 45.73 mN/m to 66.51 mN/m. The hydrophilicity potential variations following the plasma treatment were measured by the x-ray photoelectron spectroscopy examination of polar functional groups. Furthermore, surface changes after plasma treatment were examined using atomic force microscopy. The MTT assay showed no changes in cell viability cytotoxicity following the PLA films’ plasma treatment. Moreover, as evidenced by SEM analysis, plasma treatment was found to promote cell growth and adhesion to polymer surfaces. The results were suggestive of modifications due to the PLA’s plasma treatment that may enhance the biological properties of PLA as a scaffold.
Thesis
Depuis la nuit des temps, l’homme a fabriqué et utilisé des produits cosmétiques. De la Gauleà l’Egypte, en passant par l’Empire Romain et la Grèce antique, les hommes et les femmess’appliquaient sur le visage et le corps des produits naturels ou transformés (huiles, poudres,mixtures, laits, etc.) afin de s’embellir, de se soigner ou de se laver [1]. Ce rituel, aujourd’huiquotidien, représente un marché de 425 milliards d’euros, où la France se positionne enleader, en détenant environ 25% de parts de marché [2]. Si le geste existe toujours, lesproduits ont beaucoup changé, leurs formulations et leurs actions ont su s’adapter à lademande des consommateurs. Cette demande s’oriente actuellement vers une diminution del’utilisation des additifs, notamment lorsque leur innocuité est remise en cause. La loiLachaud, adoptée en 2011 à l’Assemblée Nationale, en est le parfait exemple, en proposantl’interdiction d’utiliser les phtalates, parabènes et alkyphénols dans les produits cosmétiques,généralement utilisés comme conservateurs dans les formulations, pour limiter la proliférationmicrobienne (bactéries, champignons, etc.) [3]. Dans ce contexte, et en dépit de la liste deconservateurs autorisés dans les produits cosmétiques établie par la Commission Européenne,où l’on retrouve par exemple le Triclosan ou le Zinc Pyrithione [4], la fabrication de produitssans conservateurs est actuellement une tendance forte dans l’industrie cosmétique, enréponse à une demande forte du marché.
Article
The immobilization of Ag-TiO2 nanoparticles (NPs) on polymer fabrics creates many additional functions for conventional fabrics such as water purification, self-cleaning, UV blocking and antibacterial properties and has been of increasing interest to researchers. However, it is difficult to load functional NPs on some fabrics with low surface energy; therefore, an environmentally friendly and effective technology is urgently needed to address this problem. In this work, dual DBD plasma treatment was applied to synthesis of Ag-TiO2 functionalized polypropylene (PP) fabrics for the first time. Compared with other methods of loading Ag NPs on the fiber cloth substrates such as chemical reduction, UV reduction and melt mixing, the technique utilized in this work has the characteristics of being environmentally friendly, of high efficiency, firm loading and economical. Air DBD plasma treatment was applied to introduce polar groups onto PP fiber surfaces for the subsequent hydrothermal reaction to load TiO2 NPs on the PP fabric surface. Ag NPs with the desired particle size and homogeneously distribution were then in situ reduced by H2 DBD plasma treatment. The corresponding experimental mechanisms are also discussed.
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Modification of the surface layer of polyurethane with plasma-immersion ion implantation (PIII) and studying its physical and chemical changes have been discussed in this paper. The goal of the research was to obtain carbonized layer allowing creating biocompatible polyurethane implants. The experiments of PIII treatment in various modes were performed. The investigation of the modified surface characteristics was carried out by observing the kinetics of free surface energy for two weeks after treatment. The regularities between treatment time and the level of free surface energy were detected. The explanation of high energy level was given through the appearance of free radicals in the surface layer of material. The confirmation of the chemical activation of the polyurethane surface after PIII treatment was obtained.
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Polytetrafluoroethylene (PTFE) is widely used for constructing tissue replacements, particularly clinically used vascular prostheses, and is also applied in dental and orthopedic surgery, thanks to its non‐toxicity, high chemical resistance, low surface energy and excellent thermal stability. We report here on a comparative study in which PTFE is modified with the use of DC argon plasma (8 W, 240 s) and is coated with hydrogenated or oxidized nanodiamonds (mean size 5 nm), with a view to achieving improved body acceptance of the bio‐inert pristine material. The surface morphology characterized by scanning electron microscopy reveals a microscale and nanoscale structuring of the PTFE foils with comparable roughness among all samples (analyzed by atomic force microscopy). The water contact angle remains in the highly hydrophobic range (above 100°). However, the proliferation and metabolic activity of primary human hFOB 1.19 osteoblasts (studied for up to 7 days) are significantly enhanced by the plasma and/or by hydrogenated nanodiamond treatment (rather than by oxidized nanodiamond treatment) of the PTFE foil.
Article
To employ advantageous tunable magnetic properties of metal phthalocyanines (Pcs) in practical devices it is necessary to bind them to solid substrates. A simple method to bind Cu(II) and Fe(III) sulfonated phthalocyanines on plasma treated surface of polyethylene (PE) is proposed. Formation of reactive centers (radicals) on the PE surface after the plasma treatment was observed in electron-spin resonance (ESR) spectra at 330 mT and 350 mT. The signal at 350 mT disappears after grafting of the Pcs, which suggests the radical is spent on formation of a chemical bond. Successful grafting of Pcs was also confirmed by X-ray photoelectron spectroscopy and SEM-EDS measurements. In UV-Vis spectra Q and B bands typical for the π-π interaction in Pcs were observed at 620 and 340 nm, respectively. Splitting of the Q band occured due to reduction in symmetry of the peripherally substituted Pcs. Interestingly, lower concentration of CuPc solution during grafting process lead to higher amount grafted to the surface. In the case of FePc the optimum grafting concentration is higher. The ESR spectra of PE samples with grafted FePc were similar to the bulk Pcs with the high-spin state (S=5/2) of d⁵ Fe(III) ions.
Article
This review covers the use of plasma technology relevant to the preparation of dressings for wound healing. The current state of knowledge of plasma treatments that have potential to provide enhanced functional surfaces for rapid and effective healing is summarized. Dressings that are specialized to the needs of individual cases of chronic wounds such as diabetic ulcers are a special focus. A summary of the biology of wound healing and a discussion of the various types of plasmas that are suitable for the customizing of wound dressings are given. Plasma treatment allows the surface energy and air permeability of the dressing to be controlled, to ensure optimum interaction with the wound. Plasmas also provide control over the surface chemistry and in cases where the plasma creates energetic ion bombardment, activation with long-lived radicals that can bind therapeutic molecules covalently to the surface of the dressing. Therapeutic innovations enabled by plasma treatment include the attachment of microRNA or antimicrobial peptides. Bioactive molecules that promote subsequent cell adhesion and proliferation can also be bound, leading to the recruitment of cells to the dressing that may be stem cells or patient-derived cells. The presence of a communicating cell population expressing factors promotes healing.
Article
The main objective of the study is to investigate the effects of argon low temperature plasma on PLA film properties and determine the effect of storage time on the value of surface free energy and its polar and dispersive components. The effects of the different treatment time on PLA film are analyzed. The contact angle measurements and subsequent SFE calculation have been done immediately after the treatment as well as after 1, 7, 14, 30, and 60 days. Furthermore, the chemical changes have been studied using XPS and surface topography has been analyzed with confocal microscopy. The results show a significant improvement in the film wettability. This improved wettability is manifested by a 40% reduction in the contact angle of the water and a 43% increase in SFE values. Moreover, the highest values of surface free energy are noted after 6 min plasma treatment, but results for shorter treatment time such as 2–4 min are more stable over time. The SFE increases from 40.1 mJ/m² to 57.4 mJ/m² after 6 min activation, however after 60 days storage SFE value decreases to 44.8 mJ/m², compared to decrease from 56.7 mJ/m² to 50.1 mJ/m² for 2 min activation.
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A Surface Enhanced Raman Spectroscopy (SERS) system with the coupling between surface plasmon polaritons (SPPs) supported by a gold grating and localized surface plasmons (LSPs) excited on grafted copper nanoparticles (CuNPs) was designed and characterized. The excitation of copper nanoparticles–molecules–gold layer sandwich structures was studied under 633 nm wavelength irradiation. Rhodamine 6G (R6G) molecules were added onto SERS substrates and located above and between the CuNPs. Prepared samples were studied by several experimental techniques: goniometry, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrokinetic analysis. Aging of the modified PE and PET was accompanied by an increase in the contact angle, which was due to a reorientation of the molecular polar segments produced during the plasma treatment. XPS and zeta potential measurements indicated that the thiols were chemically bonded to the gold coated polymer surfaces and that the thiols mediate subsequent grafting of Cu nanoparticles. Both XPS and EDS analyses revealed that a higher concentration of grafted copper nanoparticles was achieved on the PET substrate. EDS showed that Cu nanoparticles are homogeneously distributed over the whole polymer surface. The enhancement factor was higher for PE (1.7 × 10³) compared to PET (0.9 × 10²).
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The field of material surface modification with aim of biomaterials construction involves several approaches based on surface treatments that allow to prepare materials, which support the cell adhesion and proliferation and thus aid and improve the tissue formation. Modified materials have a surface composition and morphology intended to interact with biological systems and cellular functions. Not only surface chemistry has an effect on material biological response, surface structures of different morphology can be constructed to guide a desirable biological outcome. Nano-patterned material surfaces have been tested with aim to determine how surface geometry, physical and chemical properties on a micro- and nano-scale can affect cellular response and influence cell adhesion and proliferation. Surface physico-chemical properties (e.g. chemistry, morphology, wettability, electrical conductivity, optical and mechanical properties) of treated surfaces were determined. The enhancement in cell adhesion and proliferation on modified substrates was studied in vitro. Bactericidal action of noble metal nano-particles (e.g. Au, Ag) on polymers was characterized. The influence of metal nano-particles grafting by using metal nano-particle suspension prepared by "green" methods was determined. © 2016. Published by Manufacturing Technology. All rights reserved.
Article
As space exploration moves further and further into deep space, it is a big challenge to develop antistatic inorganic thermal control coating with lightweight and strong adhesion to substrates. Herein, this work reported an inorganic antistatic AZO/Al2O3-ZnO-Y2O3 composite coating fabricated by PEO combined with ALD methods. The results show that when the Zn/Al ratio of deposited AZO film is 24:1, its overall performance is the optimal, and the emissivity, absorptivity and resistivity are 0.892, 0.409 and 1.15 × 10–3 Ω·cm, respectively, which can meet thermal control application requirements of spacecraft. Furthermore, the AZO/Al2O3-ZnO-Y2O3 composite coating shows a good electron-resistance irradiation performance, which is because AZO conductive film is easy to generate free carriers, speed up some electron transport and make electrons better disperse and conduct, thus reducing the penetration depth of electron irradiation. This work provides a material basis for thermal control system of spacecraft with long life and high reliability.
Article
Autohesion (direct-bonding or self-bonding) is the formation of bonds between two surfaces of an identical polymer at elevated temperature (usually just above Tg). It is an emerging technique that has the potential to cleanly and precisely join/bond polymers without the need for adhesives. Autohesion is particularly useful for applications that require hermetic and precise polymer bonding, such as in microfluidics, MEMS, and in the encapsulation of active medical implants. This article discusses the latest debate on the main mechanisms proposed to explain autohesion of polymers such as diffusion, crystalline growth, thermodynamic and chemical bonding. Surface activation techniques that are used to facilitate autohesion such as plasma treatment, chemicals, UV and ozone treatments are explored. In addition, topics such as molecular characteristics of polymers that influence autohesion, limits to bonding strength and hermetic bonding are critically discussed. Methods for evaluating autohesion strength of polymers are also described. Comparisons between prediction models from different research groups with experimental values for authohesive bonding strength are shown. Finally, conclusions and suggestions for further research are presented.
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This review surveys methods for the fabrication, by plasma surface treatments or plasma polymerization, of polymeric surfaces and thin plasma polymer coatings that contain reactive chemical groups useful for the subsequent covalent immobilization, by solution chemical reactions or vapor phase grafting, of molecules or polymers that can exert bio-specific interfacial responses. Surfaces containing amine, carboxy, hydroxy, and aldehyde groups are the subject of this review. Aminated surfaces have been fabricated using various plasma vapors or mixtures and have found wide use for biointerface applications. However, in many cases the amine surfaces have a rather limited shelf life, with post-plasma oxidation reactions and surface adaptation leading to the disappearance of amine groups from the surface. Aging is a widespread phenomenon that often has not been recognized, particularly in some of the earlier studies on the use of plasma-fabricated surfaces for bio-interfacial applications, and can markedly alter the surface chemistry. Plasma-fabricated surfaces that contain carboxy groups have also been well documented. Fewer reports exist on hydroxy and aldehyde surfaces prepared by plasma methods. Hydroxy surfaces can be prepared by water plasma treatment or the plasma polymerization of alkyl alcohol vapors. Water plasma treatment on many polymer substrates suffers from aging, with surface adaptation leading to the movement of surface modification effects into the polymer. Both hydroxy and aldehyde surfaces have been used for the covalent immobilization of biologically active molecules. Aging effects are less well documented than for amine surfaces. This review also surveys studies using such surfaces for cell colonization assays. Generally, these surface chemistries show good ability to support cell colonization, though the effectiveness seems to depend on the process vapor and the plasma conditions. Carboxylate co-polymer surfaces have shown excellent ability to support the colonization of some human cell lines of clinical interest. Immobilization of proteins onto plasma-carboxylated surfaces is also well established.
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Polyethylene (PE) was irradiated with inert Ar plasma, and the chemically active PE surface was grafted with Au nanoparticles. The composition and the structure of the modified PE surface were studied using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Changes in the surface wettability were determined from the contact angle measured in a reflection goniometer. The changes in the surface roughness and morphology were followed by atomic force microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMC) or mouse NIH 3T3 fibroblasts, and their adhesion and proliferation were studied. We found that plasma discharge and Au grafting lead to dramatic changes in the surface morphology and roughness of PE. The Au nanoparticles were found not only on the sample surface, but also in the sample interior up to the depth of about 100 nm. In addition, plasma modification of the PE surface, followed with grafting Au-nanoparticles, significantly increased the attractiveness of the PE surface for the adhesion and growth of VSMC, and particularly for mouse embryonic 3T3 fibroblasts. (C) 2009 Elsevier B.V. All rights reserved
Article
We present a technique to fabricate polymer substrates with locally structured surfaces in the nanometer scale. By ion projection direct cross-linking the surface of a stretched polymer is locally cross-linked and afterwards annealed above the glass transition temperature to induce surface rippling. The rippling periodicity depends on the thickness of the cross-linked surface layer, formed through hydrogen vacancies, which are generated by the ion bombardment. We systematically studied the effect of the projectile mass on the hydrogen vacancy distribution in polystyrene (PS) samples. Simulations revealed a decreasing depth of the maximum hydrogen vacancy numbers by increasing projectile mass. This value can be correlated to the thickness of the cross-linked PS layer, which directly determines the ripple periodicity. An additional Au capping layer was used to further reduce the cross-linked layer thickness to a few nanometers. By this, defined structures with a ripple periodicity of 250 nm were fabricated. In addition, the technique allows inferring the Young’s modulus of thin cross-linked PS layers.
Article
AFM, XRD, zeta (ζ) potential measurement and spectroscopic ellipsometry were used for characterization of thin (20nm) Au films sputtered onto polyethyleneterephthalate (PET). Sputtered Au film shows significantly different surface morphology and roughness in comparison with pristine PET. From XRD measurement of 20nm thick sputtered Au layers it was found that Au crystalizes preferentially in (111) direction with lattice parameter of a=0.40769nm, density of ρ=19.338gcm−3 and lattice stress of about 230MPa. Higher surface conductance of Au/PET by ζ-potential measurement was found. Au layer thickness of 19.4nm determined from spectroscopic ellipsometry was in good agreement with the AFM estimated value of 20nm.
Article
The chemical bonding at metal–polymer interface is believed to play an important role in adhesion. The interfacial bonding and consequently adhesion are directly influenced by the way in which the interface is formed. Modification of a polytetrafluoroethylene surface (PTFE) has developed into an attractive way to chemically alter a polymer. Such synthetic approaches potentially can maintain a polymer's desirable bulk properties but can provide new different interfacial properties. There are many methods by which polymer surfaces can be chemically modified. Most common examples of this chemistry are reactions that introduce a single metal atom, a single type of functional group or mixture of functional groups. This paper briefly summarizes some existing as well as some newer examples from our laboratory of an alternative metal coating chemistry by which PTFE surface has covered with a thin and uniform metal sodium layer. In order to study the nature of the bond formation at metal/polymer interface, we have investigated the interaction of sodium atoms with a polytetrafluoroethylene fragment. Our results suggest that sodium bound to a PTFE polymer chain is energetically favorable. The compound formation is accompanied by charge transfer between sodium and polymer. PTFE with new interfacial properties is well recognized in many areas. Requirements to join dissimilar materials are more and more frequent in new technologies. The paper also deals with a study of a joint between aluminium pieces and polytetrafluoroethylene (PTFE) pieces. The way of their joining is described. The joint was performed through soldering with adhesive that covered the joining surfaces of the pieces, processed at a certain roughness, in a well established thickness layer. The joint was achieved through particular procedure of soldering, simultaneous with plastic deformation of the metal. Various tests of the joint were carried out under conditions simulating service conditions. A piece joint was tested in terms of its strength, thermal resistance and tightness. The tests showed a very good tightness of the joint at high vacuum (1.333×10−9mbar), in conditions of repeated thermal shocks, in the range of temperatures between −195.5 and 270°C. The study took into account the requirements of the particular tests and relevant foreign standards, including ASTM and DIN.
Article
Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108–58° and 65.2°, respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction.
Article
Polypropylene samples were exposed to argon plasma discharge and the changes of the PP surface properties were studied by different methods. Surface wettability was derived from contact angle measured by standard goniometry and chemical structure of the plasma modified PP was studied using X-ray photoelectron spectroscopy (XPS) and by Rutherford backscattering spectroscopy (RBS), surface morphology and roughness of samples using AFM. Zeta potential of pristine and modified PP was determined with the SurPASS. The presence of incorporated oxygen in the PP surface layer, about 60nm thick, was observed in RBS spectra. Oxygen concentration is a decreasing function of the depth. With progressing aging time the oxygen concentration on the PP surface decreases. Plasma treatment results in a rapid decrease of the contact angle, which increases again with increasing aging time. In XPS measurement the oxygen containing structures, created by the plasma treatment, were found on the very surface of the modified PP and the zeta potential being changed too. The significant difference in zeta potential between pristine and plasma treated PP clearly indicates that the plasma treatment leads to a more hydrophilic PP surface.
Article
Polyethylene (PE) surface was modified by Ar plasma discharge. The changes of surface morphology and surface wettability (characterized by contact angle) were followed using AFM microscopy and standard goniometry, respectively. The changes of chemical structure of PE polymeric chain were characterized by FTIR and XPS techniques. A nanoindenter was used to study mechanical properties (microhardness, elasticity module and microscratch test) of modified PE. After exposition to the plasma discharge a fast decline of the contact angle is observed. The decline depends on the discharge power and the time elapsed from the plasma exposition. FTIR and XPS measurements indicate an oxidation of degraded polymeric chains and creation of hydroxyl, carbonyl, ether, ester and carboxyl groups. Surface morphology of modified PE depends on the plasma discharge power and exposure time. Maximum microhardness and elastic module, observed on PE specimens exposed to plasma discharge for 240s, may be connected with PE crosslinking initiated by plasma discharge.
Article
Structural changes induced by Ar plasma discharge in low and high density polyethylene (LDPE and HDPE) were studied by different techniques. AFM and SEM methods were used to determine surface morphology, the changes in chemical structure were followed using FTIR and UV–vis spectroscopy. The content and the depth profile of incorporated oxygen was determined by RBS method. The degree of polymer ablation was determined gravimetrically. Standard goniometry was used to determine contact angle and to follow aging of plasma modified polymer. As a result of plasma treatment a lamellar structure or spherulites appear on the surface of HDPE and LDPE, respectively. Pronounced increase of the surface roughness is observed on HDPE contrary to LDPE. Plasma treatment for 400s leads to the ablation of the surface layer of about 0.6 and 1μm thick for LDPE and HDPE, respectively. Plasma treatment results in oxidation of the polymer surface layer which is more pronounced in HDPE. Concentration maximum of incorporated oxygen lies 25nm beneath the sample surface in both polymer types. After exposure to plasma discharge carbonyl, carboxyl and amide groups were detected in the polymer surface layer together with CC bonds either in aromatic or in aliphatic structures. Immediately after the plasma treatment strong decline of the contact angle is observed, the decline being larger in HDPE. Later, in aged specimens the contact angle increases rapidly. The increase, which may be due to rearrangement of degraded structures, is stronger in the specimens exposed to plasma for longer times.
Article
The effects of remote nitrogen plasma and nitrogen plasma on medical PVC's surface modification are studied. The surface properties are characterized by the contact angle measurement, X-ray photoelectron spectroscopy and scanning electron microscopy. Results show that the remote nitrogen plasma treatments modify the PVC surface in both morphology and composition and the treatment by the remote nitrogen plasma in PVC surface modification is more effective than that by the nitrogen plasma. Remote nitrogen plasma can modify the surface more uniformly. After the PVC surface is treated for 2 min by remote nitrogen plasma, the [w(O)+ w(N)]/w(C)] value increases from 0.13 to 0.51 and the water contact angle decreases from 89o to 18o.
Article
Ablation and water etching of high density polyethylene (PE) exposed to Ar plasma for 240s at 8.3W power were studied. Gravimetry was used to determine the ablated and etched layer thicknesses. The surface topography and roughness were observed via AFM. The chemical composition and structure of modified surface layer were studied by FTIR, XPS, RBS, and EPR techniques. It was found that under the experimental conditions ca. 30nm thick layer is ablated, the surface topography changes dramatically and surface roughness increases. The cleavage of macromolecular chains is proved by the presence of surface free radicals. Oxygen containing groups known to enhance surface solubility are detected. Under present laboratory conditions ca. 20nm thick surface layer is dissolved during 24h. After water dissolution of the surface, the roughness increases.
Article
Polytetrafluoroethylene (PTFE) films were treated by non-equilibrium microwave plasma of a mixture of water vapor and argon at low pressure. The properties of the PTFE surface were evaluated by means of contact angle measurements, adhesion strength measurements, attenuated total reflectance infrared spectrometry (ATR IR), and X-ray photoelectron spectrometry (XPS). The influence of some plasma parameters, such as microwave power and treatment time, has been studied. H2O/Ar plasma treatment led to a significant decrease of the water contact angle from 110.0° to 23.6° under the optimal condition, which resulted from the substantial surface defluoration and the introduction of an unusual amount of oxygen and polar functions as revealed by XPS and ATR IR spectra. When the treated samples were kept in air at room temperature, the contact angles increased markedly within a few days probably due to the evolution of chemical composition and structure of the treated PTFE surface during storage. Nevertheless, after the contact angle had reached a constant value of 60°, the plasma-treated PTFE still exhibited significantly improved wettability. Adhesion strength was improved from 26.7 to 583Ncm−2, a factor of 22, after plasma treatments.
Article
The means by which plasma treatment enhances the adhesion of polymer materials, remains obscure. Thus far, two possible mechanisms have been proposed: an increase in surface energy, and the anchor effects imparted by plasma etching. Independently from these mechanisms, reactions between free radicals, generated by plasma irradiation and adhesives are also likely to affect the adhesive properties of polymer materials. Free radicals generated on polyethylene (PE) by glow-discharge plasma were exposed to air and converted to peroxide. The peroxides were converted back to free radicals with the application of heat, and then graft polymerization was initiated, by adding a hydrophilic monomer such as acrylic acid. The peroxides formed by the reaction between free radicals and the oxygen in air was detected by chemiluminescence (CL). In this work, plasma-treated PE surfaces were bonded to aluminum boards, using epoxy resin as an intermediate adhesive and then subjected to a series of peeling tests. The sample with the highest peeling strength also had the highest level of CL-detected peroxides. These findings suggest that the free radicals generated by plasma treatment influence the adhesive properties of the polymer materials.
Article
X-ray photoelectron spectroscopy (XPS) has been used to study the chemical effects of both inert (argon) and reactive (oxygen, nitrogen, and mixed gas) plasma treatments done in situ on a variety of polymer surfaces. Inert gas plasma treatments introduce no new detectable chemical species onto the polymer surface but can induce degradation and rearrangement of the polymer surface. However, plasma treatments with reactive gases create new chemical species which drastically alter the chemical reactivity of the polymer surface. These studies have also shown that the surface population of chemical species formed after plasma treatment is dependent on both the chemical structure of the polymer and the plasma gas. The effects of direct and radiative energy-transfer processes in a plasma have also been studied. Polymers containing certain functional groups were found to be more susceptible to damage via radiative energy transfer. Ageing studies of plasma-modified polymer surfaces exposed to the atmosphere have shown that the ageing process consists of two distinct phases. The initial phase, which occurs rapidly, involves adsorption of atmospheric contaminants and, in some cases, specific chemical reactions. The second phase, which occurs slowly, is due to surface reorganization.
Article
Plasma treatment of polymers encompasses a variety of plasma technologies and polymeric materials for a wide range of applications and dates back to at least the 1960s. In this article we provide a brief review of the United States patent literature on plasma surface modification technologies and a brief review of the scientific literature on investigations of the effects of plasma treatment, the nature of the plasma environment, and the mechanisms that drive the plasma–surface interaction. We then discuss low‐radio‐frequency capacitively coupled nitrogen plasmas and their characteristics, suggesting that they provide significant plasma densities and populations of reactive species for effective plasma treatments on a variety of materials, particularly when placing the sample surface in the cathode sheath region. We further discuss surface chemical characterization of treated polymers, including some results on polyesters treated in capacitively coupled nitrogen plasmas driven at 40 kHz. Finally, we connect plasma characterization with surface chemical analysis by applying a surface sites model to nitrogen uptake of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) treated in a 40 kHz nitrogen plasma. This example serves to suggest an interesting practical approach to comparisons of plasma treatments. In addition, it suggests an approach to defining the investigations required to conclusively identify the underlying treatment mechanisms.
Article
Argon plasma treatment and subsequent atmospheric exposure have been used to incorporate new oxygen functionalities at the surface of polystyrene (PS) and polypropylene (PP). High-energy resolution X-ray photoelectron spectroscopy (XPS) has yielded molecular information regarding the site of modification in both polymers. Core level and valence band spectra have been interpreted. We have adopted a simple subtraction process to highlight the changes occurring in the valence band spectra upon treatment. In the case of PS, modification is found to be occurring at ring sites. In PP, modification is thought to be occurring at two sites. We propose that modification at the tertiary carbon site leads to chain scission and subsequent etching, while modification at the methyl side group results in functionalities being incorporated at the polymer surface. These data help to substantiate mechanisms that were previously proposed, based on the accepted mechanisms of cross-linking vs chain scission for these polymers.
Article
The surface of oxygen-plasma-treated polystyrene (PSox) was investigated using X-ray photoelectron spectroscopy (XPS), streaming potential measurements and a dynamic study of the wetting properties at different pH (Wilhelmy plate method). The PSox surface is functionalized with various oxygen-containing groups, including carboxyl functions, and must be viewed as covered by a polyelectrolyte which swells depending on pH. The wetting hysteresis, its evolution upon repeated cycles and the influence of pH are controlled by the dissolution of functionalized fragments and the retention of water upon emersion; the retained water may evaporate progressively and allow macromolecule compaction and/or reorientation. Modification of the PSox surface upon aging in dry atmosphere, humid atmosphere, and water was studied using XPS and dynamic wetting measurements. Aging in water provoked the dissolution of PSox macromolecular chains, as indicated by adsorption of released fragments on a check PS sample placed nearby. However, the concentration of functionalized molecules at the surface of water-aged PSox was still sufficient to allow swelling at pH 5.6 and 11.0. Hydrophobicity recovery was faster in humid air (R. H. 95%) compared to dry air (R. H. 5%), due to the plasticizing effect of water. Hydrophobicity recovery upon aging in air was reversed quickly by immersion at pH 5.6 or 11.0, due to deprotonation and swelling.
Article
Surface modification of polymers by pulsed plasma has been investigated to minimize degradation reactions occurring at the same time as the surface modification reactions. The hydrogen radical, ion, and electron concentrations in the hydrogen plasma were simulated as a function of the elapsed time after turning off the discharge. The contact angle measurement showed that hydrogen plasma treatment, regardless of pulsed or continuous plasma, led to degradation reactions as well as defluorination and oxidation on PTFE surfaces. The degradation reactions of PTFE chains initiated by the pulsed hydrogen plasma were not as vigorous as those by the continuous hydrogen plasma. A combination of the on-time/off-time of 30/270μs in the pulsed hydrogen plasma was efficacious in modifying PTFE surfaces. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 340–348, 2002
Article
Atomic force microscopy (AFM), contact-angle measurements, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize biaxially oriented poly(propylene) (PP) films modified by exposure to a corona discharge. Surface analysis was performed on PP filmsmodified at various corona energies to explore the changes in surface topography, wettability, and oxidation state resulting from the corona treatment. Even at low corona energies, water-soluble low-molecular-weight oxidized materials (LMWOM) are formed. These LMWOM products agglomerate into small topographical mounds that are visible in the AFM images. For the detection of LMWOM on corona-treated surfaces, AFM appears to be at least as sensitive as contact-angle measurements or ESCA. A major advantages of AFM relative to the other surface analytical techniques used to confirm the presence of the LMWOM is that no washing of the surface with water is required in conjunction with the AFM analysis.
Article
This paper reports, in a comparative method, the effect of dielectric barrier discharge (DBD) plasma and radio frequency (RF) plasma on the surface wettability, chemistry and microstructure changes of the surface of polytetrafluroethylene (PTFE). Both types of plasma could improve the PTFE surface wettability significantly owing to the changes in surface chemistry and surface microstructure. The high-energy species in high-vacuum (HV) plasma cause the PTFE surface severely etched and causing decomposition of outmost layer of PTFE, results in the evolution of tetrafluoroethylene via scission of the (CF 2) n chain to yield oligomeric segments. In comparison, few heavy species in DBD plasma have high enough energy to cause the scission of the (CF 2) n chain to yield oligomeric segments, thus less etching effect. The contact angle variation with energy dose on RF plasma-treated surface demonstrated a two-stage decrease behaviour: an initial fast decrease stage followed by a levelled-off stage. In comparison, three stages of behaviour are evident for DBD plasma-treated surface. A drastic decrease of the contact angle was recorded during early DBD plasma treatment (at low energy dose), followed by a steady stage and then a slow recovery stage.
Article
Little information has been published concerning the interaction of gold with polymers. In the context of this lack of information, we decided to investigate the effect of Ar plasma treatment on the surface properties of poly(ethylene terephthalate) (PET) in order to examine its possible application for metal-polymer adhesion improvement. The plasma treatment leads to an immediate increase of the PET's surface wettability, which however significantly depends on the sample aging, more specifically on the time elapsed after the treatment. X-ray photoelectron spectroscopy (XPS) measurements revealed that the oxygen concentration in the surface-near layers increases as a result of the treatment, but that it also changes with time for the samples in contact with the atmosphere, probably as a result of polar group rearrangements. Plasma initiated ablation and Au sputtering increases the surface roughness. The nanoindenter measurements revealed that the treatment increases the microhardness of treated PET. Contrary to hardness, the elastic modulus decreases. Scratch tests showed that the deformation of samples consisting of Au coatings deposited on both pristine and treated PET was elastic rather than plastic. We conclude from the nanoindenter data that the plasma modification does not affect the adhesion of gold on PET, but the X-ray diffractometry (XRD) analysis showed that the Au film deposited on the as-treated PET, and on PET aged for 14 d are the most stable.
Article
Polytetrafluoroethylene (PTFE) was treated in a low-power plasma using a series of feed gases (O2, Ar, N2 and NH3) and the resulting surface modifications were evaluated by x-ray photoelectron spectroscopy, static secondary ion mass spectroscopy, dynamic contact angle measurements and atomic force microscopy. All plasma treatments caused light etching, but the nature and extent of chemical modification varied considerably. Fluorine depletion of the surface was affected most efficiently by Ar and least effectively by O2 plasma. New functionalities were introduced to the surface either from plasma derivatives of the feed gases or by post-treatment exposure to moist air; Ar, N2 and NH3 were more effective than O2 in this respect. The wettability of virgin and plasma-treated materials in phosphate-buffered saline solution (PBS) and 1-bromonaphthalene was studied, and the observations are discussed in a framework that correlates contact-angle hysteresis with surface chemistry in a semi-quantitative manner. In Part II of this work, further changes of the surface chemistry and wettability of virgin and plasma-treated materials arising due to storage in PBS or air are described. Copyright © 2001 John Wiley & Sons, Ltd.
Article
In this work it was investigated the effect of the exposure to different plasmas on the wettability of silicone samples. We have observed that oxygen. argon, and hydrogen glow discharges are quite effective in reducing the water contact angle of such polymer. However, indifferently to efficiency of the treatment, practically all the modified surfaces recovered great part of their original hydrophobicity. We have investigated this hydrophobic recovery using surface energy measurements and theoretical simulations based on the exponential decay of the population of polar groups on the surface. According to our results such recovery can be attributed to the decrease of polar species at the interface water–polymer surface.
Article
The graft polymerization of acrylic acid (AAc) was carried out onto poly(tetrafluoroethylene) (PTFE) films that had been pretreated with remote argon plasma and subsequently exposed to oxygen to create peroxides. Peroxides are known to be the species responsible for initiating the graft polymerization when PTFE reacts with AAc. We chose different parameters of remote plasma treatment to get the optimum condition for introducing maximum peroxides (2.87 × 10−11 mol/cm2) on the surface. The influence of grafted reaction conditions on the grafting degree was investigated. The maximum grafting degree was 25.2 μg/cm2. The surface microstructures and compositions of the AAc grafted PTFE film were characterized with the water contact angle meter, Fourier-transform infrared spectroscopy (ATR–FTIR) and X-ray photoelectron spectroscopy (XPS). Contact angle measurements revealed that the water contact angle decreased from 108° to 41° and the surface free energy increased from 22.1 × 10−5 to 62.1 × 10−5 N cm−1 by the grafting of the AAc chains. The hydrophilicity of the PTFE film surface was greatly enhanced. The time-dependent activity of the grafted surface was better than that of the plasma treated film.
Article
Persistent surface morphologies in extruded polymer substrates can be generated in a first step by projecting a mask with argon ions and, secondly, by a consecutive exposure to solvent. In the first step, the polymer is locally cross-linked as a consequence of the interaction of the Ar-ions with –C–H-groups. During the second step, protrusions occur owing to swelling, which persist after removal of the solvent. The morphology of the protrusions can be tuned by choosing the right set of the experimental parameters, i.e. the ion dose, the size and distance of the holes in the mask, and their height by the duration of swelling.
Article
Polyethylene (PE) was treated in Ar plasma discharge and then grafted from methanol solution of 1,2-ethanedithiol to enhance adhesion of gold nano-particles or sputtered gold layers. The modified PE samples were either immersed into freshly prepared colloid solution of Au nano-particles or covered by sputtered, 50 nm thick gold nano-layer. Properties of the plasma modified, dithiol grafted and gold coated PE were studied using XPS, UV-VIS, AFM, EPR, RBS methods and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain, creation of excessive free radicals and conjugated double bonds. After grafting with 1,2-ethanedithiol the concentration of free radicals declined but the concentration of double bonds remained unchanged. Plasma treatment changes PE surface morphology and increases surface roughness too. Another significant change in the surface morphology and roughness was observed after deposition of Au nano-particles. The presence of Au on the sample surface after the coating with Au nano-particles was proved by XPS and RBS methods. Nanoindentation measurements shown that the grafting of plasma activated PE surface with dithiol increases significantly adhesion of sputtered Au nano-layer. (C) 2009 Elsevier B.V. All rights reserved
Article
The irradiation of polymer surfaces with ion beams leads to pronounced chemical and physical modifications when the ions are scattered at the atoms in the polymer chain. In this way, different products of decomposition occur. Here we show that by changing the ion fluence and the mass of the ion the local mechanical properties as Young's modulus of a polystyrene surface layer can be tailored. By annealing prestretched irradiated PS near the glass transition, surface rippling occurs in the irradiated areas only, which can be described with an elastic model. The moduli obtained from rippling periodicities and elastic model assumptions are in the range between 8 and 800 MPa at the glass transition and characterize the irradiated PS as rubberlike. From these values the network density and the molar mass of entanglement are quantified. The obtained network density equals the density of hydrogen vacancies generated through the scattered ions, as confirmed by simulations of the atomic scattering and displacement processes. The obtained molar mass of entanglement reveals that the PS locally was densely cross-linked. Our results show that even for nondiscrete layered polymer systems relevant polymer parameters can be derived from the well-known surface rippling without the need for costly chemical analysis.
Article
Plasma treatment of polymer surfaces is used to control the generation of topological surface structures: stripes, starlike morphologies, and pinnacles in the range from 100 nm up to several micrometers. These protrusions arise when the plasma-treated polymer surface is exposed to an organic solvent (liquid or vapor phase). The distribution density and the height of the observed structures on the surface are functions of the power density of the plasma reactor and the exposure time to the plasma, the duration of the development process, the type of the polymer, and its manufacturing. We suggest that the structures are generated by selective swelling of less cross-linked areas within the polymer surface and not by rearrangement or dissolution of polymer chain fragments created by plasma, or by amphiphilic moieties due to oxidation as a consequence of plasma treatment.
Article
A general drawback observed with plasma treatment is the limited stability of the hydrophilic-treated surfaces toward washing, storage, or heating. It has recently been found that oxygen, air, or argon radiofrequency plasmas with higher intensities than normally used can give hydrophilic surfaces having good wash stability. High intensity oxygen plasma treatment of polystyrene and polycarbonate surfaces was therefore carried out using two different capacitively coupled RF reactors with internal shelf electrodes. The obtained surface characteristics and stability were evaluated using contact angle measurements, XPS, AFM, and nanoindentation. For both materials, low water contact angles were found to correlate with high surface oxygen content. Only the surfaces exposed to relatively intense treatments, with self-bias voltages above 140 V (polystyrene) or 240 V (polycarbonate), could withstand washing in ethanol and remain highly hydrophilic. Substantial amounts of nonsoluble material were observed on the plastic substrates after treatment. Furthermore, for polycarbonate Young's modulus of the surface was found to increase with increasing intensity of the plasma. These observations were taken as an indication that extensive cross-linking of the surface layer took place. After more than 6 months of storage, the samples treated with the most intense plasmas (self-bias voltages in the range of 480-600 V) still had water contact angles around 20 degrees .
Conference Paper
Chip multiprocessors (CMP) are a convenient way of leveraging from the technological trends to build high-end and embedded systems that are performance and power efficient, while exhibiting attractive properties such as scalability, reliability and ease of design. However, the onchip interconnect for moving the data between the processors, and between the processors and memory subsystem, plays a crucial role in CMP design. We present a novel approach to optimizing its power by exploiting the value locality in data transfers between processors. A communicating value cache (CVC) is proposed to reduce the number of bits transferred on the interconnect, and simulation results with several parallel applications show significant energy savings with this mechanism. Results show that the importance of our proposal will become even more significant in the future.