File Name: plasma deposition treatment and etching of polymers .zip
Plasma polymers are unconventional organic thin films which only partially share the properties traditionally attributed to polymeric materials.
- Optics Express
- Plasma Processing for Tailoring the Surface Properties of Polymers
- Plasma polymerization and plasma modification of polymer surfaces
- Optics Express
Plasma polymers are unconventional organic thin films which only partially share the properties traditionally attributed to polymeric materials. For instance, they do not consist of repeating monomer units but rather present a highly crosslinked structure resembling the chemistry of the precursor used for deposition.
Due to the complex nature of the deposition process, plasma polymers have historically been produced with little control over the chemistry of the plasma phase which is still poorly understood.
Yet, plasma polymer research is thriving, in par with the commercialisation of innumerable products using this technology, in fields ranging from biomedical to green energy industries.
Here, we briefly summarise the principles at the basis of plasma deposition and highlight recent progress made in understanding the unique chemistry and reactivity of these films. We then demonstrate how carefully designed plasma polymer films can serve the purpose of fundamental research and biomedical applications. We finish the review with a focus on a relatively new class of plasma polymers which are derived from oxazoline-based precursors. This type of coating has attracted significant attention recently due to its unique properties.
Plasma in its natural state can be seen as the polar lights and lightning. Humans artificially induce plasmas using a variety of energy sources including strong magnetic fields, lasers, radiofrequency, electric fields and microwaves.
Man-made plasmas are nowadays seen everywhere from commodities such as TV screens, toys and low energy lighting to nuclear reactors and aircraft propulsion turbines. What may be less obvious for some are all industrial uses of plasmas, not as a finished product, but as a manufacturing tool for material surface modification [ 1 ].
Plasmas are constituted of highly energetic molecules, molecular fragments, ions, radicals and free electrons. As a result, when plasmas come in contact with solid surfaces, may it be metal, plastic or any other material, they cause important changes to the material surface properties. In this way, it is possible to use plasma-assisted processes to modify a material surface energy, wettability, chemistry and even topography to suits a variety of applications with the added advantage that the properties of the bulk materials are preserved.
Plasma-assisted surface modifications encompass a range of techniques which Chu et al. Yet, plasma-induced surface treatments processes are used to create novel materials with unique electronic, optical, mechanical and biological properties for many different fields of applications.
When the excited species present in the plasma generated from inert Ar, Ne, He … or reactive O 2 , N 2 , NH 3 , CO 2 … gases collide with the solid, enough energy may be acquired by the atoms on the surface layer of the solid for them to detach from the surface. When the physical degradation of the bulk material is limited to the outermost layer, the plasma process is called sputtering, Figure 1 a [ 3 ]. This is the process used in plasma cleaners to remove impurities from contaminated surfaces.
If further deeper loss of the exposed material occurs, however, the process is referred to as plasma etching, Figure 1 b. Plasma etching is a process in which the adsorption of energetic species is followed by product formation, prior to product desorption [ 4 ].
Combination processes have also been reported where anisotropic chemical etching is accelerated by ion sputtering [ 5 ]. In biomaterials engineering, plasma is generally used for surface cleaning and sterilisation but at its extreme, plasma etching can also be used for surface roughening and nanopatterning, and even generating novel nanostructures [ 6 , 7 , 8 , 9 ]. It is also possible for excited species present in the plasma phase to directly react with the substrate and induce surface modification including the grafting of new chemical functions, such as amine or hydroxyl groups [ 10 ].
This process is often referred to as plasma ion implantation. The downside of modifying a surface via plasma sputtering or implantation is that the modification is short lived because reorientation of the surface functional group occurs overtime [ 11 , 12 , 13 , 14 ]. Surfaces with lasting properties that completely differ from those of the bulk materials can be generated via plasma polymer deposition.
It differs from the other plasma-assisted surface modification in the fact that a thin organic coating is formed over the surface of the original material Figure 1 d. Figure 1 provides an simplified visual representation of the main class of plasma surface modification processes, in which the effect of plasma-wall interaction and particle distribution in the sheath region have not been represented.
Important phenomena occurring in this region are still under fervent investigation [ 15 , 16 ]. The figure also does not represent the influence of reactor geometry on the plasma deposition process. The interested reader can refer to an article by Whittle et al. Plasma-assisted surface modification processes a sputtering b etching c implantation and d polymer deposition. In this review, we highlight the versatile nature of organic thin films deposited from plasma.
We then provide specific examples where carefully designed plasma polymers are used to generate model substrates with controlled surface properties to elucidate fundamental research questions from nanowetting mechanisms to protein adsorption.
We illustrate the most recent advances in plasma polymer applications to novel technologies ranging from the development of prosthetic materials, diagnostic devices and even hydrocarbon recovery technologies. Finally, we discuss a new class of plasma polymers that are based on oxazoline precursors pioneered recently by our team.
We should stress that this review is not intended to cite all papers published in this exciting field. It is rather intended to summarise recent advances while referring the reader to reviews published by others where a particular aspect of the field is described. Plasma-assisted deposition is a coating technique used to form thin polymer-like films on surfaces. Plasma-enhanced chemical vapour deposition PECVD is one of the most common plasma polymerization techniques.
It uses plasmas of volatile organic precursors to create polymeric films at low or atmospheric pressure [ 18 ]. While plasma polymerization can be performed by a variety of others means such as magnetron sputtering, liquid-assisted deposition, plasma-assisted thermal evaporation, etc. One intrinsic advantage of PECVD is that it is a dry technique which only uses a minimal amount of precursors and does not produce liquid organic waste. As such, the method is cost effective and environmentally friendly [ 19 , 20 , 21 ].
The great advantage of plasma polymer deposition compared to conventional techniques for thin film deposition is the capacity to deposit the same surface chemistry with the same conditions on practically any type of substrate material [ 22 , 23 , 24 , 25 ]. This is because after the initial deposition of a few angstroms of material, the film growth becomes substrate independent [ 22 , 23 ]. In contrast, techniques for surface modification such as layer-by-layer L-b-L and Self Assembled Monolayers SAMs require substrates with highly specific properties, which narrows opportunities for applications [ 26 ].
The films generated are commonly referred to as plasma polymers although they do not formally classify as polymers because they do not consist of repeating monomer units. Instead, they are formed of a variety of precursor fragments and recombination products, and are generally highly crosslinked.
Historically, such films have been produced with little control over the chemistry of the plasma phase. Despite the use of advanced techniques directly in the plasma phase such as Mass Spectroscopy, Langmuir probes and Optical Emission Spectroscopy, the mechanisms of plasma polymerization remain poorly understood [ 27 , 28 , 29 , 30 ]. However, advances in surface characterization techniques and the pull for applications have fueled much progress in this area, and it is now possible to control deposition conditions in many ways so that chemistry and functionality of the resulting coating can be finely tailored to suit specific applications ranging from wearable electronics [ 31 ] and solar cells [ 32 ] all the way to water treatment [ 33 ].
It is also possible to deposit plasma polymers onto micro and nanomaterials as well as powders. This approach has been used to create adsorbents for water treatment purposes. Silica or magnetic nanoparticles can be coated with a hydrophobic plasma polymer layer to remove hydrocarbon residue from waste water [ 33 , 34 ].
Thiophene-coated particles are able to isolate heavy metals [ 35 ], and allylamine-coated powders successfully remove dyes from waters which is relevant for the leather, textile, paper, pharmaceuticals, paper and food industries [ 36 ]. Plasma polymers coatedmagnetic nanoparticles were even recently used to remove haze proteins from wines [ 37 , 38 ].
The first degree of freedom when designing a plasma polymer is the monomer choice amongst a wealth of precursors [ 39 ]. Plasma polymers can be deposited from practically any compound volatile enough to be introduced into the reaction chamber. Table 1 provide examples of organic precursors commonly used to produce thin polymeric films from their plasma phase. This list includes monomers like ethanol which are difficult to polymerise via conventional means but can be deposited into a polymeric film using plasma processes [ 29 , 40 ].
It also includes examples of precursors containing sulfur and fluoro heteroatoms which can provide very interesting reactivity and wetting properties. Another interesting example is that of oxazolines.
Following classic organic chemistry routes, oxaolines are polymerized via ring opening polymerization which results in a linear polymer with amide repeating units. Several works have demonstrated that the plasma deposition of oxazolines generates surface chemistries that are not achievable via conventional means, including the formation of isocyanate and nitrile groups but also the retention of the oxazoline ring itself.
The presence of intact oxazoline rings provides unique opportunities to conduct binding reactions of biomolecules, nanoparticles and various ligands that carry carboxyl acid groups in their structures [ 41 , 42 ]. Other groups have investigated the plasma deposition of other ring-containing monomers with heteroatoms including pyrrole [ 43 ], furfuryl [ 44 ], thiophene [ 45 ], aniline [ 46 ] and even essential oils [ 47 , 48 , 49 ].
Plasma polymers prepared from non-synthetic monomers are a particularly hot topic because they combine desirable optical and physical properties with biocompatibility and environmental sustainability [ 50 , 51 ].
However, as the complexity of the monomer increases, so does the importance of carefully tuning the plasma deposition condition to tailor the amount of functionality retention to suit any specific application [ 52 , 53 ] and ensure that film reactivity can be maintained for relevant aging time [ 54 ]. Examples of common organic precursors used to prepare plasma-deposited film with different surface chemistry.
Plasma polymers are a coating of choice for biomedical applications. The topic has been extensively reviewed elsewhere [ 76 , 77 ]. Plasma polymer deposition enables the generation of surfaces where the entire spectrum of surface properties including chemistry, wettability, stiffness and nanotopography can be precisely tailored.
The technique is rapid and reproducible; thus, it is possible to create large quantities of model surfaces with well-controlled properties for the investigation of many complex processes, ranging from protein binding, to immune response through to the fundamentals of nano-wetting. They are also underpinning new biosensing platforms [ 78 ] and novel cell guidance surfaces. We used a capacitively coupled parallel plate plasma chamber [ 22 ] to generate films from a variety of organic precursors including allylamine, octadiene, aldehyde, ethanol, acrylic acid or even perfluorooctane.
The resulting coatings present distinctive chemical functions, namely, amines, hydroxyls, carboxylic acids, ketones, etc. These plasma polymers have been used as a utility to investigate the systematic effect of surface chemistry on many biological processes including the biofunctionality of surface-adsorbed proteins [ 40 ], the differentiation of embryonic [ 79 ], kidney [ 80 ], dental pulp [ 81 ], mesenchymal [ 82 ] and human adipose-derived stem cells [ 83 , 84 ] as well as the deposition of collagen by primary human dermal fibroblasts [ 85 ].
Using the reactivity of the chemical groups created, it is also possible to bind ligands and even proteins to create diagnostic tools [ 40 , 86 , 87 , 88 , 89 ]. Fine-tuned chemical functionality facilitated by plasma polymers also allowed binding to surfaces of gold and silver nanoparticles to generate model surface nanotopography to study biological phenomena or solve environmental challenges [ 25 , 90 , 91 , 92 , 93 ], and nanoengineered surfaces with controlled nanofeatures size and density [ 94 ].
In this manner, uniform and gradient nanotopography can be generated using electrostatic binding of gold or silver nanoparticles capped with mercapto succinic acid to allylamine plasma polymers or covalent binding to oxazoline-based coatings [ 95 ]. A thin layer of plasma polymer can then be deposited on top of the surface nanotopography to control the outermost surface chemistry while preserving nanotopography. This is a unique approach that can be achieved only by plasma polymerization or iCVD.
An important application of this approach was to derive understanding of the influence of surface nanotopography and chemistry on inflammatory responses [ 96 , 97 ]. Such knowledge is vital for the utilization of plasma polymers in implantable devices [ 98 , 99 ]. When plasma polymers are combined with nanotexturing, remarkable wetting states such as superhydrophobicity and superhydrophilicity can be achieved [ , , ]. We nanoengineered model gradient substrates with intrinsic wettability ranging from hydrophilic to hydrophobic to investigate the mechanisms governing wetting at the nanoscale.
While classical theories could not account correctly for the water contact angles measured on nanorough surfaces, we were able to develop an empirical model that effectively captures the experimental data. The model, which is now known as the Vasilev-Ramiasa equation [ ], further enables us to predict the water contact angle on the nanorough surfaces, using as the only known parameter the number density and size of the spherical nanofeatures and the contact angle on the smooth substrate itself.
A range of other biomedical applications have also been facilitated by plasma polymers including in drug delivery allowing to achieve controlled release rate of synthetic therapeutics or biomolecules [ , , ]. Another particularly useful application of plasma polymers is in antibacterial technologies [ , , ].
Infections are a well-studied subject and it is now well-known that the attachment of individual planktonic bacterial cells to the device surface is just the first step, followed by colonization and infection.
It is also well understood that once a biofilm is formed, it protects the bacterial cells from the immune system and enormously up to times increases the dose of antibiotics required to clear the infection. This overuse of antibiotics leads, on the one hand, to development of antibiotic resistance by bacteria and, on the other hand, causes systemic toxicity to organs such as the kidneys and liver. For these reasons, the purpose of antibacterial coatings is to disturb the initial stage of bacterial adhesion [ , ].
This can be achieved through one of four distinct mechanisms of action: contact killing, bacterial repellence, killing in solution or stimuli responsive killing [ ]. Plasma polymers have been used to generate contact killing surfaces on several occasions [ , ].
Plasma Processing for Tailoring the Surface Properties of Polymers
Plasma Deposition, Treatment, and Etching of Polymers takes a broad look at the basic principles, the chemical processes, and the diagnostic procedures in the interaction of plasmas with polymer surfaces. This recent technology has yielded a large class of new materials offering many applications, including their use as coatings for chemical fibers and films. Additional applications include uses for the passivation of metals, the surface hardening of tools, increased biocompatibility of biomedical materials, chemical and physical sensors, and a variety of micro- and optoelectronic devices. Appeals to a broad range of industries from microelectronics to space technology Discusses a wide array of new uses for plasma polymers Provides a tutorial introduction to the field Surveys various classes of plasma polymers, their chemical and morphological properties, effects of plasma process parameters on the growth and structure of these synthetic materials, and techniques for characterization Interests scientists, engineers, and students alike. Posting Komentar. Plasma Deposition, Treatment, and Etching of Polymers PDF By:Riccardo d'Agostino Published on by Elsevier Plasma Deposition, Treatment, and Etching of Polymers takes a broad look at the basic principles, the chemical processes, and the diagnostic procedures in the interaction of plasmas with polymer surfaces. Appeals to a broad range of industries from microelectronics to space technology Discusses a wide array of new uses for plasma polymers Provides a tutorial introduction to the field Surveys various classes of plasma polymers, their chemical and morphological properties, effects of plasma process parameters on the growth and structure of these synthetic materials, and techniques for characterization Interests scientists, engineers, and students alike This Book was ranked at 4 by Google Books for keyword Depositions.
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Plasma polymerization and plasma modification of polymer surfaces
Morosoff, An Introduction to Plasma Polymerization. Cramarossa, F. Fracassi, and F. Illuzzi, Plasma Polymerization of Fluorocarbons.
New Methods of Polymer Synthesis pp Cite as. A plasma partially ionized gas can be utilized to form polymeric materials. The former case represents the synthesis of a new polymeric material by plasma polymerization, and in the latter case a new polymeric material is synthesized by means of plasma modification of a polymer surface.
This chapter details how plasma treatments can be used to tailor the wettability of polymers. A plasma is an excited gas, and exposure of a polymer to a plasma discharge generally results in an enhancement in surface energy and associated with this is an increase in wettability. The effect however can be short lived due to hydrophobic recovery. In this review the use of both low and atmospheric plasmas for the activation of polymers will be discussed, as will the use of these plasmas for the deposition of plasma polymerised coatings. The latter can be used to produce polymer surfaces with tailored functionalities, thus achieving stable water contact angles ranging from superhydrophilic to superhydrophobic, as required.
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