Patterned and layered hydrophilic/phobic coatings were deposited on multiple surfaces using nonfluorinated precursors (AA, acrylic acid; PMA, propargyl methacrylate) with an atmospheric pressure dielectric barrier discharge operating in open air. Water contact angles of the resulting films could be tuned from <5°(superhydrophilic) to >135°(very hydrophobic) by adjusting the AA/PMA feed ratio and/or via postdeposition exposure of films to an Ar/O 2 plasma treatment. Coatings could be applied to any surface and were seen to be water stable, due in large part to cross-linking induced from the reactivity of the PMA pendant groups. Hybrid hydrophilic/phobic patterns at submillimeter length scales, and philic/phobic/philic laminates were produced using a shadow mask and sequential deposition, respectively. Chemical heterogeneity of films was assessed using XPS, SIMS, and micro-IR imaging and suggest that localization of COOH and OH groups are primarily responsible for hydrophilicity. Overall, this work demonstrates that atmospheric pressure plasma polymerization is a simple and scalable method for robust and tunable control of wettability of surfaces of all kinds.
The electrochemical nucleation and growth (EN&G) on active surface sites has been a concept of fundamental and technological interest for several decades. Here, we have studied the EN&G of Cu on glassy carbon with a new perspective using scanning electrochemical cell microscopy (SECCM), in combination with scanning electron microscopy, atomic force microscopy, and X‐ray photo-electron spectroscopy. Unlike the conventional macroscopic approach, we leveraged the spatial resolution of the SECCM to probe individual sites on the same surface, independently from each other, revealing regions with different energy barriers for nucleation and a distribution of activities for EN&G at the microscopic scale. This site-dependent activity can be modified with common surface pretreatments (i. e., polishing and preanodization). We addressed the electrochemical diversity through multiple descriptors and used them to conduct statistical analysis, supported by surface characterization techniques, bringing forward information that is simply unavailable with the conventional macroscopic approach. This work serves as a departure point to conceive new analysis strategies and address the real nature of active sites for nucleation.
Many papers dealing with the surface analysis of plasma polymers or plasmamodified polymers report the use of X-ray photoelectron spectroscopy (XPS) to quantify the surface composition. However, most of the time, quantification is performed using software that includes an equation based on the assumption that the sample is homogeneous in composition. However, for plasma-treated samples, this is often not the case. The usual analysis of XPS spectra does not allow the exact quantification in the case of an inhomogeneous sample. In this paper, we show that it is possible to obtain a depth profile of the composition, and a more accurate surface composition by using another mathematical approach for surface quantification, being QUASES Tougaard.depth profile, plasma-polymerized propargyl methacrylate, QUASES Tougaard, water contact-angle (WCA), XPS
Textile industry is constantly searching for easy and rapid ways to improve the properties of textiles. In this matter, plasma treatments have already proven to be an efficient and green solution, as they proceed in a dry environment and require minimal use of chemicals. To date, most of the work on the subject has been performed with low‐pressure plasmas. Recently, atmospheric plasmas have received increasing interest, especially for industrial applications. Indeed, the possibility to avoid the use of pumping systems makes this technology easily implementable in continuous in‐line processes. For many applications, the treatment aims at modifying the textile surface to increase the overall hydrophilicity. The latter is often probed by the water contact angle, but this does not always reflect the global hydrophilic behavior of the textile as a three‐dimensional material. A complementary study of the wicking properties is important to better reflect the penetration of liquids into the textile, but it is poorly reported in the literature. The present work aims at increasing the water uptake of polyethylene terephthalate (PET) textile by direct or remote plasma treatment, which are the two main trends in this field. For this purpose, a dielectric barrier discharge (DBD) and a radiofrequency plasma torch at atmospheric pressure are used, respectively. Different plasma parameters are varied and their respective effect on the wicking properties of the fabric, assessed by an absorbency test developed ad hoc, are correlated to their surface chemical composition determined by X‐ray photoelectron spectroscopy. These results are compared with the possible changes in wetting of the fiber surface witnessed by water contact angles measured on PET foil samples submitted to the same plasma treatments. Complete wicking of water in PET textile can be obtained after 20 or 10 s of torch treatment with pure Ar plasma or Ar/O2 mixture, respectively. However, a comparable effect is detected, after 30 s of DBD Ar plasma treatment, under the used experimental conditions. Besides, the addition of O2 to the discharge has an opposite effect on the fabric wicking. These results are discussed in terms of the peculiar processes in surface activation and modification of the fabric surface triggered by the two different plasma technologies.
In this work, immobilization of the often unwanted filaments in dielectric barrier discharges (DBD) is achieved and used for one‐step deposition of patterned coatings. By texturing one of the dielectric surfaces, a discharge containing stationary plasma filaments is ignited in a mix of argon and propargyl methacrylate (PMA) in a reactor operating at atmospheric pressure. From PMA, hydrophobic and hydrophilic chemical and topographical contrasts at sub‐millimeter scale are obtained on silicon and glass substrates. Chemical and physical characterizations of the samples are performed by micrometer‐scale X‐ray photoelectron spectroscopy and infrared imaging and by water contact angle and profilometry, respectively. From the latter and additional information from high‐speed imaging of the plasma phase and electrical measurements, it is suggested that filaments, denser in energetic species, lead to higher deposition rate with higher fragmentation of the precursor, while surface discharges igniting outwards the filaments are leading to smoother and slower deposition. This work opens a new route for a one‐step large‐area chemical and morphological patterning of surfaces at sub‐millimeter scales. Moreover, the possibility to separately deposit coatings from filaments and the surrounding plasma phase can be helpful to better understand the processes occurring during plasma polymerization in filamentary DBD.
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