Search

This work aims to provide new insights into the link between the growth mechanisms of functionalized plasma polymer films (PPFs) and the substrate temperature (TS). By means of AFM‐based techniques, it has been demonstrated that the mechanical behavior of the coatings is dramatically affected by TS and the precursor employed (i.e., 1‐propanethiol or 1‐propylamine). While propylamine‐based PPFs behave as hard elastic materials regardless of TS, propanethiol‐based PPFs evolve from viscous liquids to elastic solids with increasing TS. This behavior can be understood considering the glass transition temperature of PPF. For both precursors, the latter is correlated to the cross‐linking density controlled through the energy density brought by positive ions to the growing film. [ABSTRACT FROM AUTHOR]

A new plasmonic biosensor was developed in a planar chip-based format by coupling the plasmonic properties of gold nanoparticles (Au NPs) with the mechanical and bioadhesive features of unconventional organic thin films deposited from plasma, namely primary amine-based plasma polymer films (PPFs). A self-assembled layer of spherical Au NPs, 12 nm in diameter, was electrostatically immobilized onto optically transparent silanised glass. In the next step, the Au NP layer was coated with an 18 nm polymeric thick PPF layer via the simultaneous polymerization/deposition of a cyclopropylamine (CPA) precursor performed by radio frequency discharge, both in pulsed and in continuous wave modes. The CPA PFF surface plays the dual role of an adsorbent towards negatively charged chemical species as well as an enhancer of plasmonic signals. The biosensor was tested in a proof-of-concept series of experiments of human serum albumin physisorption, and chosen as a model system for blood serum. The peculiar surface features of CPA PPF, before and after the exposure to buffered solution of fluorescein isothiocyanate-labelled human serum albumin (FITC-HSA), were investigated by a multi-technique approach, including UV-visible and X-ray photoelectron spectroscopies, atomic force microscopy, scanning electron microscopy, contact angle and surface free energy measurements. The results showed the very promising potentialities from both bioanalytical and physicochemical points of view in scrutinizing the macromolecule behavior at the biointerface. [ABSTRACT FROM AUTHOR]

In this work, nanobiohybrids of plasmonic gold nanoparticles (AuNP, anti-angiogenic) and a peptide mimicking the vascular endothelial growth factor (VEGF, pro-angiogenic) were assembled and scrutinized in terms of physicochemical characterization, including optical properties, surface charge, surface chemical structure and morphology of the bioengineered metal nanoparticles, for their potential application as multifunctional theranostic (i.e., therapy + sensing) nanoplatform (AuNP/VEGF). Specifically, a peptide sequence encompassing the VEGF cellular receptor domain 73–101 (VEGF73–101) and its single point cysteine mutated were immobilized onto AuNP by physi- and chemi-sorption, respectively. The new hybrid systems were characterized by means of a multitechnique approach, including dynamic light scattering (DLS) analyses, zeta potential (ZP), spectroscopic (UV-Vis, FT-IR, XPS), spectrometric (TOF-SIMS) and microscopic (AFM, SEM) techniques. Proof-of-work cellular experiments in human umbilical vein endothelial cells (HUVEC) upon the treatment with AuNP/VEGF samples, demonstrated no toxicity up to 24 h (MTT assay) as well an effective internalization (laser confocal microscopy, LSM). [ABSTRACT FROM AUTHOR]

In the context of protecting Mg‐based nano‐objects for potential hydrogen storage applications, the potential of C:H layer as a barrier polymer material deposited by the plasma‐enhanced chemical vapor deposition process is examined. Corrosion tests reveal (a) good barrier properties of the C:H layer and (b) suggest an increase in the internal stress with the power dissipated in the plasma. The latter is attributed to an increase in the cross‐linking density of the coatings accompanied by an increase in the stiffness as shown by nanoindentation measurements. Finally, for a given set of plasma parameters, Mg‐based nanowires were successfully enrobed by the C:H coatings as evidenced by scanning electron microscopy measurements. [ABSTRACT FROM AUTHOR]

Hybrid materials consisting of nanocrystalline metal oxide films coated with molecules have considerable implications for the development of optoelectronic devices. We report on a straightforward and versatile procedure to engineer stable layers made of molecules chemisorbed on the surface of mesoporous inorganic metal oxides. The procedure is based on a thermal copper-free Huisgen reaction, which is directly conducted on TiO2 or NiO nanocrystalline films, between already bound diketopyrrolopyrrole sensitizers substituted by two azido groups and a crosslinking agent consisting of a tetrapropiolate ester. The procedure is mild and simple and does not require a catalyst, since quantitative conversion is obtained by a simple heating of the photoelectrode into a solution of the crosslinking agent. The photoelectrodes were characterized by ToF-SIMS, femtosecond transient absorption spectroscopy, electrochemistry and were finally used to fabricate dye-sensitized solar cells with iodide/triiodide and cobalt trisbipyridine complexes as redox mediators. Important increased stability of the crosslinked films was demonstrated by desorption and cyclic voltammetry experiments. Transient absorption spectroscopy and photovoltaic measurements showed that the dyes keep their initial photoelectrochemical properties upon crosslinking. This bottom-up approach is certainly broadly applicable and opens the possibility to make "chemistry on the electrode" to functionalize and crosslink dyes with any component. [ABSTRACT FROM AUTHOR]

It is accepted that the macroscopic properties of functional plasma polymer films (PPF) are defined by their functional density and their crosslinking degree ( χ ) which are quantities that most of the time behave in opposite trends. If the PPF chemistry is relatively easy to evaluate, it is much more challenging for χ . This paper reviews the recent work developed in our group on the application of principal component analysis (PCA) to time-of-flight secondary ion mass spectrometric (ToF-SIMS) positive spectra data in order to extract the relative cross-linking degree ( χ ) of PPF. NH 2 -, COOR- and SH-containing PPF synthesized in our group by plasma enhanced chemical vapor deposition (PECVD) varying the applied radiofrequency power ( P RF ), have been used as model surfaces. For the three plasma polymer families, the scores of the first computed principal component (PC1) highlighted significant differences in the chemical composition supported by X-Ray photoelectron spectroscopy (XPS) data. The most important fragments contributing to PC1 (loadings > 90%) were used to compute an average C/H ratio index for samples synthesized at low and high P RF . This ratio being an evaluation of χ , these data, accordingly to the literature, indicates an increase of χ with P RF excepted for the SH-PPF. These results have been cross-checked by the evaluation of functional properties of the plasma polymers namely a linear correlation with the stability of NH 2 -PPF in ethanol and a correlation with the mechanical properties of the COOR-PPF. For the SH-PPF family, the peculiar evolution of χ is supported by the understanding of the growth mechanism of the PPF from plasma diagnostic. The whole set of data clearly demonstrates the potential of the PCA method for extracting information on the microstructure of plasma polymers from ToF-SIMS measurements. [ABSTRACT FROM AUTHOR]

Plasma polymer films are more and more used in numerous applications such as the day-to-day packaging, which requires a good mechanical resistance of the coating. Since mechanical properties are function of the cross-linking degree of the thin films, it is important to understand the relationship between the two. In this work, plasma polymer films were studied in terms of cross-linking degree and mechanical properties, measured by means of ToF-SIMS coupled to PCA and depth-sensing nanoindentation, respectively. The data reveal that when the power increases, the films are more cross-linked and show higher hardness, higher elastic recovery, lower creep strain and an increased ability for self-healing. As the plasma polymer films are more cross-linked, the plasticity drops and the viscoelasticity and hardness increase. [ABSTRACT FROM AUTHOR]

Nanostructured niobium oxide (NO) semiconductors are gaining increasing attention as electronic, optical, and electro-optic materials. However, the preparation of stable NO nanofilms with reproducible morphology and behavior remains a challenge. Here we show a rapid, well-controlled, and efficient way to synthesize NO films with self-organized columnlike nanostructured morphologies and advanced functional properties. The films are developed via the growth of a nanoporous anodic alumina layer, followed by the pore-directed anodization of the Nb underlayer. The columns may grow 30–150 nm wide, up to 900 nm long, with an aspect ratio of up to 20, being anchored to a thin continuous oxide layer that separates the columns from the substrate. The as-anodized films have a graded chemical composition changing from amorphous Nb2O5 mixed with Al2O3, Si-, and P-containing species in the surface region to NbO2 in the lower film layer. The post-anodization treatments result in the controlled formation of Nb2O5, NbO2, and NbO crystal phases, accompanied by transformation from nearly perfect dielectric to n-type semiconductor behavior of the films. The approach allows for the smooth film growth without early dielectric breakdown, stress-generated defects, or destructive dissolution at the respective interfaces, which is a unique situation in the oxide films on niobium. The functional properties of the NO films, revealed to date, allow for potential applications as nanocomposite capacitor dielectrics and active layers for semiconductor gas microsensors with the sensitivity to ethanol and the response to hydrogen being among best ever reported. [ABSTRACT FROM AUTHOR]

In this work, the plasma polymerization of propanethiol is investigated with the aim to control the thiol density [SH] in the coatings. The results reveal a nearly constant evolution of [SH] regarding the mean power dissipated in the discharge. This peculiar behavior is explained considering (i) mass spectrometry data revealing a similar relative concentration of condensable SH-bearing species in the plasma and (ii) similar energetic conditions at the growing film/plasma interface. Finally, it is observed that the low 〈 P〉 synthesized films are not chemically stable in solution likely due to the release of H2S molecules trapped in the material network. The whole set of our data allows to provide a deeper understanding of the growth mechanism of propanethiol plasma polymer, essential for future development. [ABSTRACT FROM AUTHOR]

In this work, we report on the synthesis of ethyl lactate-based plasma polymer film (ELPPF) by plasma enhanced chemical vapour deposition (PECVD). Using a design of experiments, it appears that, among other, the injected power ( PRF) is the key parameter affecting the ELPPF features. Indeed, we observe a strong decrease of the COO-C/H functionalities (from 12 to 2 at.%) within a limited PRF domain. A more precise analysis of the film chemistry by combining XPS and chemical derivatization reveals that up to 95% of these carboxyl-based functions are esters. On the other hand, we show that the cross-linking degree of the ELPPF can be increased by a factor of two as a function of PRF. This work paves the way for the tailoring of the barrier properties of ELPPF by controlling the ester content and the cross-linking degree of the PPF. [ABSTRACT FROM AUTHOR]

ABSTRACT This work aims to investigate the influence of the substrate temperature on low‐pressure plasma polymerization processes. Emphasis is placed on the mechanical properties and growth mechanism of the plasma polymer films (PPFs). For this purpose, two precursors are considered, differing only by their unsaturation degree: 2‐propen‐1‐ol (CH2═CH–CH2–OH) and propan‐1‐ol (CH3–CH2–CH2–OH). Although propan‐1‐ol‐based PPFs behave like hard elastic solids, 2‐propen‐1‐ol‐based coatings evolve from a liquid film to an elastic solid on increasing the substrate temperature. This behavior is understood considering the evolution of the glass transition temperature of PPFs. The latter is correlated with the cross‐linking degree of the polymeric network governed by the energy density of bombarding ions on the growing film. [ABSTRACT FROM AUTHOR]

This paper presents a methodology to quantify oxidizing and reducing gases using n-type and p-type chemiresistive sensors, respectively. Low temperature sensor heating with pulsed UV or visible light modulation is used together with the application of the fast Fourier transform (FFT) to extract sensor response features. These features are further processed via principal component analysis (PCA) and principal component regression (PCR) for achieving gas discrimination and building concentration prediction models with R2 values up to 98% and RMSE values as low as 5% for the total gas concentration range studied. UV and visible light were used to study the influence of the light wavelength in the prediction model performance. We demonstrate that n-type and p-type sensors need to be used together for achieving good quantification of oxidizing and reducing species, respectively, since the semiconductor type defines the prediction model's effectiveness towards an oxidizing or reducing gas. The presented method reduces considerably the total time needed to quantify the gas concentration compared with the results obtained in a previous work. The use of visible light LEDs for performing pulsed light modulation enhances system performance and considerably reduces cost in comparison to previously reported UV light-based approaches. [ABSTRACT FROM AUTHOR]

Back Cover: This paper aims at identifying the mechanisms controlling the evolution of the thiol content and the chemical stability in aqueous solution of propanethiol plasma polymers. A detailed description combining film analysis and plasma diagnostic assisted by a theoretical approach is provided. Further details can be found in the article by Damien Thiry et. al. on page 606. [ABSTRACT FROM AUTHOR]

Abstract This work aims at presenting an innovative method for tailoring the morphology of functionalized plasma polymer films (PPF). The approach is based on the formation of a plasma polymer bilayer system in which the two layers differ by their chemical composition and cross-linking degree. As a case study, propanethiol-based plasma polymer films have been investigated. As revealed by a much higher S/C ratio than in the propanethiol precursor (i.e. 0.83 vs 0.33), it has been demonstrated that the bottom layer contains a large fraction of trapped sulfur-based molecules (e.g. H 2 S). When further covered by a denser PPF formed at higher energetic conditions, a three-dimensional morphological reorganization takes place giving rise to the micro/nano structuration of the organic material. The shape, the dimensions as well as the density of the generated structures are found to depend on the thickness of both coatings involved in the bilayer structure, offering a great flexibility for surface engineering. Annealing experiments unambiguously confirm the major role played by the sulfur-based trapped molecules for inducing the reshaping process. The whole set of data clearly paves the way for the development of an innovative approach for finely tailoring the morphology of functionalized PPF at the micro/nano scale. Highlights • Synthesis of a bilayer system formed by two different propanethiol plasma polymers • Formation of micro/nano structured sulfur-based plasma polymers • Study of the reshaping mechanism [ABSTRACT FROM AUTHOR]

The actual surface termination and lateral size of a nanomaterial is crucial in its interaction with biomolecules at the aqueous interface. Graphene oxide (GO) nanosheets have been demonstrated as promising nanoplatform for both diagnostic and therapeutic applications. To this respect, ‘smart’ GO nanocarriers have been obtained by the surface functionalisation with polymers sensitive, e.g., to pH, as the polyacrylate (PAA) case. In this work, hybrid GO/PAA samples prepared respectively at low (GOPAA thin ) or high (GOPAA thick ) monomer grafting ratio, were scrutinised both theoretically, by molecular dynamic calculations, and experimentally by a multitechnique approach, including spectroscopic (UV–visible, fluorescence, Raman, Attenuated-total reflectance-Fourier transformed infrared and X-ray photoelectron spectroscopies), spectrometric (time-of-flight secondary ion and electrospray ionisation mass spectrometries) and microscopic (atomic force and confocal microscopies) methods. The actual surface termination, evaluated in terms of the relative ratio between polar and dispersive groups at the surface of the GO/polymer systems, was found to correlate with the average orientation of hydrophilic/hydrophobic domains of albumin, used as model protein. Moreover, the comparison among GO, GO-PAA thin and GO-PAA thick in the optical response at the interface with aqueous solutions, both at acid and at physiological pH, showed that the hybrid GO-polymer platform could be suitable not only to exploit a pH-triggered drug release but also for a modulation of the GO intrinsic emission properties. Energy transfer experiments on the GO/polymer oxide/fluorescein-labelled albumin/doxorubicin assembly showed significant differences for GO and GO-PAA samples, thus demonstrating the occurrence of different electronic processes at the hybrid nano-bio-interfaces. Confocal microscopy studies of cellular uptake in neuroblastoma cells confirmed the promising potentialities of the developed nanoplatform for applications at the biointerface. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication of sensors based on tungsten trioxide nanowires decorated with osmium oxide nanoparticles using the aerosol-assisted chemical vapor deposition (AACVD) technique. This methodology allows the obtention of different osmium oxide decoration loadings on the tungsten oxide nanowires. The morphological and chemical characteristics; and the structural properties of the sensing layers of the sensors were studied using different techniques such as FESEM, HR-TEM, and ToF-SIMS. The gas sensing properties were analyzed for pure tungsten trioxide sensors and tungsten trioxide loaded with osmium exposed to nitrogen dioxide, hydrogen, and ethanol, thus assessing the impact of the loading on the sensor response. A sensor array comprising pure and osmium-loaded tungsten oxide devices coupled to multivariate pattern recognition techniques is shown to perform well in gas identification and quantification tasks, offering promising implications in the field of gas sensing technology., Competing Interests: The authors declare no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

New nanostructured metasurfaces capable change the composition and physical properties upon pulse laser excitation recently received a marked attention for nanophotonic technologies. In this study, well adherent to the metal substrate and significantly thicker nanoplatelet-shaped MoS 2 -based arrays were synthesized by one pot hydrothermal way via addition of ethanolamine in the synthesis solution containing ammonium heptamolybdate and thiourea. It was shown that the lightening of this material with green light ns-laser pulses at a suitable fluencies results in the detachment of organic species and compositional transformations to significantly pure MoS 2 material. For characterization the synthesized products scanning electron microscopy (SEM), glancing angle X-ray diffraction (GA-XRD), diffuse reflection, Raman, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) methods before and following green light picosecond laser pulse illumination were applied. We envisaged that these films can be successfully used as metamaterial for laser writing.

Nowadays, the development of synthetic methods regarding the fabrication of -SH containing organic coatings continues to attract a considerable attention. Among the potential techniques, the plasma polymerization appears as one of the most promising method but the difficulty to control the chemical composition of the layers is highly limiting. In this context, in this work, we report on an original method combining dry and wet chemistry approaches in view of selectively incorporating -SH functions in organic coatings. Our strategy is based on the (i) synthesis of a bromine-containing plasma polymer film, followed by (ii) a selective grafting of dithiol-based molecule on C-Br bond. Investigating the plasma polymerization process has revealed that, in our experimental window, the load of energy in the discharge has little influence on the chemical composition as well as on the cross-linking degree of the layers. This behavior is explained by considering the concomitant influence of the gas-phase reactions and the supply of energy to the growing film through ion bombardment. With regard to the functionalization strategy, based on comparative X-ray photoelectron spectroscopy measurements, it has been unambiguously demonstrated that a selective reaction between propanedithiol and the C-Br bond acting as the reactive center takes place resulting in the removing of the bromine atom and the incorporation of -SH groups in the PPF. Depending on the grafting reaction duration, the relative proportion of carbon bearing the -SH group is found to evolve from 4 to 6%. On the other hand, the dissolution of unbounded bromine-based species in the liquid medium during the grafting procedure is also evidenced. The whole set of our results clearly demonstrates the attractiveness of our strategy paving the way for new development in the fabrication of -SH-rich-containing organic thin films.

Plasma polymer films (PPF) have increasing applications in many fields due to the unique combination of properties of this class of materials. Among notable features arising from the specifics of plasma polymerization synthesis, a high surface reactivity can be advantageously used when exploited carefully. It is related to the presence of free radicals generated during the deposition process through manifold molecular bond scissions in the energetic plasma environment. In ambient atmosphere, these radicals undergo autoxidation reactions resulting in undesired polymer aging. However, when the reactivity of surface radicals is preserved and they are put in direct contact with a chemical group of interest, a specific surface functionalization or grafting of polymeric chains can be achieved. Therefore, the control of the surface free radical density of a plasma polymer is crucially important for a successful grafting. The present investigation focuses on the influence of the hydrocarbon precursor type, aromatic vs aliphatic, on the generation and concentration of free radicals on the surface of the PPF. Benzene and cyclohexane were chosen as model precursors. First, in situ FTIR analysis of the plasma phase supplemented by density functional theory calculations allowed the main fragmentation routes of precursor molecules in the discharge to be identified as a function of energy input. Using nitric oxide (NO) chemical labeling in combination with X-ray photoelectron spectroscopy analysis, a quantitative evaluation of concentration of surface free radicals as a function of input power has been assessed for both precursors. Different evolutions of the surface free radical density for the benzene- and cyclohexane-based PPF, namely, a continuous increase versus stabilization to a plateau, are attributed to different plasma polymerization mechanisms and resulting structures as illustrated by PPF characterization findings. The control of surface free radical density can be achieved through the stabilization of radicals due to the proximity of incorporated aromatic rings. Aging tests highlighted the inevitable random oxidation of plasma polymers upon exposure to air and the necessity of free radical preservation for a controlled surface functionalization.

The improvement of the (bio)adhesive properties of elastomeric polydimethylsiloxane (PDMS) coatings is reported. This is achieved by a surface modification consisting of the incorporation of block copolymers containing a PDMS block and a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block in a PDMS matrix, followed by matrix cross-linking and immersion of the obtained materials in water. Contact angle measurements (CA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) showed the presence of the PDMAEMA block at the surface, drastic morphology changes, and improved adhesion properties after immersion in water. Finally, underwater bioadhesion tests show that mussels adhere only to block copolymer-filled coatings and after immersion in water, i.e., when the PDMAEMA blocks have been brought to the coating surface. These observations highlight the significant role of hydrophilic groups in the surface modification of silicone coatings.

Thiol-supported surfaces draw more and more interest in numerous fields of applications from biotechnology to catalysis. Among the various strategies to generate such surfaces, the plasma polymerization of a thiol-containing molecule appears to be one of the ideal candidates. Nevertheless, considering such an approach, a careful characterization of the material surface chemistry is necessary. In this work, an original chemical derivatization method aiming to quantitatively probe the -SH functions in plasma polymers was established using N-ethylmaleimide as a labeling molecule. The method was qualitatively and quantitatively validated on self-assembled monolayers of 3-mercaptopropyltrimethoxysilane exhibiting a -SH-terminated group used as "model" surface. For a quantitative determination of the -SH content in propanethiol plasma polymers, the kinetics of the reaction was investigated. The latter is described as a two-step mechanism, namely a fast surface reaction followed by a diffusion-limited one. The density of -SH groups deduced from the derivatization method (~4%) is in good agreement with typical values measured in some other plasma polymer families. The whole set of our data opens up new possibilities for optimizing the -SH content in thiol-based plasma polymer films.

Two strategies were used for the preparation of hyperbranched polymer brushes with a high density of functional groups: (a) the cathodic electrografting of stainless steel by poly[2-(2-chloropropionate)ethyl acrylate] [poly(cPEA)], which was used as a macroinitiator for the atom transfer radical polymerization of an inimer, 2-(2-bromopropionate)ethyl acrylate in the presence or absence of heptadecafluorodecyl acrylate, (b) the grafting of preformed hyperbranched poly(ethyleneimine) onto poly(N-succinimidyl acrylate) previously electrografted onto stainless steel. The hyperbranched polymer, which contained either bromides or amines, was quaternized because the accordingly formed quaternary ammonium or pyridinium groups are known for antibacterial properties. The structure, chemical composition, and morphology of the quaternized and nonquaternized hyperbranched polymer brushes were characterized by ATR-FTIR reflectance, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The peeling test confirmed that the grafted hyperbranched polymer films adhered much more strongly to stainless steel than the nongrafted solvent-cast films. The quaternized hyperbranched polymer brushes were more effective in preventing both protein adsorption and bacterial adhesion than quaternary ammonium containing poly(cPEA) primary films, more likely because of the higher hydrophilicity and density of cationic groups.

A two-step "grafting from" method has been successfully carried out, which is based on the electrografting of polyacrylate chains containing an initiator for the atom transfer radical polymerization (ATRP) of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) or copolymerization of TBAEMA with either monomethyl ether of poly(ethylene oxide) methacrylate (PEOMA) or acrylic acid (AA) or styrene. The chemisorption of this type of polymer brushes onto stainless steel surfaces has potential in orthopaedic surgery. These films have been characterized by ATR-FTIR, Raman spectroscopy, atomic force microscopy (AFM), and measurement of contact angles of water. The polymer formed in solution by ATRP and that one detached on purpose from the surface have been analyzed by size exclusion chromathography (SEC) and (1)H NMR spectroscopy. The strong adherence of the films onto stainless steel has been assessed by peeling tests. AFM analysis has shown that addition of hydrophilic comonomers to the grafted chains decreases the surface roughness. According to dynamic quartz crystal microbalance experiments, proteins (e.g., fibrinogen) are more effectively repelled whenever copolymer brushes contain neutral hydrophilic (PEOMA) co-units rather than negatively charged groups (PAA salt). Moreover, a 2- to 3-fold decrease in the fibrinogen adsorption is observed when TBAEMA is copolymerized with either PEOMA or AA rather than homopolymerized or copolymerized with styrene. Compared to the bare stainless steel surface, brushes of polyTBAEMA, poly(TBAEMA-co-PEOMA) and poly(TBAEMA-co-AA) decrease the bacteria adhesion by 3 to 4 orders of magnitude as revealed by Gram-positive bacteria S. aureus adhesion tests.

Novel copolymer brushes have been synthesized by a two-step "grafting from" method that consists of the electrografting of poly(2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethylacrylate) onto stainless steel, followed by the nitroxide-mediated radical polymerization of 2-(dimethylamino ethyl)acrylate and styrene or n-butyl acrylate, initiated from the electrografted polyacrylate chains. The grafted copolymers were quaternized in order to endow them with antibacterial properties. Peeling tests have confirmed the strong adhesion of the grafted copolymer onto the stainless steel substrate. Quartz crystal microbalance experiments have proven that fibrinogen adhesion is lower on the hydrophilic quaternized films compared to the nonionic counterpart. Such quaternized copolymers exhibit significant antibacterial activity against the Gram-positive bacteria S. aureus and the Gram-negative bacteria E. coli.