Nonthermal Plasma Treatment Improves Uniformity and Adherence of Cyclodextrin-Based Coatings on Hydrophobic Polymer Substrates

Abstract

Low surface energy substrates, which include many plastics and polymers, present challenges toward achieving uniform, adherent coatings, thus limiting intended coating function. These inert materials are common in various applications due to favorable bulk, despite suboptimal surface, properties. The ability to functionally coat low surface energy substrates holds broad value for uses across medicine and industry. Cyclodextrin-based materials represent an emerging, widely useful class of coatings, which have previously been explored for numerous purposes involving sustained release, enhanced sorption, and reversible reuse thereof. In this study, substrate exposure to nonthermal plasma was explored as a novel means to improve uniformity and adherence of cyclodextrin-based polyurethane coatings upon unreceptive polypropylene substrates. Plasma effects on substrates were investigated using contact angle goniometry and X-ray photoelectron spectroscopy (XPS). Plasma impact on coating uniformity was assessed through visualization directly and microscopically. Plasma effects on coating adhesion and bonding were studied with mechanical lap-shear testing and XPS, respectively. Substrate surface wettability and oxygen content increased with plasma exposure, and these modifications were associated with improved coating uniformity, adhesion, and interfacial covalent bonding. Findings demonstrate utility of, and elucidate mechanisms behind, plasma-based surface activation for improving coating uniformity, adherence, and performance on inert polymeric substrates.

Surface Functionalization of Face Masks with Cold Plasma and Its Effect in Anchoring Polyphenols Extracted from Agri-Food

“…Cold plasma treatment is a well-known and widespread technique for increasing the hydrophilicity, wettability, and adhesion characteristics of surfaces with different chemical nature and morphology. Historically, it finds application in textiles [ 1 ] where it is used to increase the dyeability of natural and synthetic fabrics, and, more recently, in the biomedical field for the immobilization of active and functional derivatives (such as cyclodextrins, dopamine, and/or antibiotic drugs) onto the uppermost layer of different substrates [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. With reference to the functionalization of polymer-based surfaces, plasma processing is particularly versatile, safe, inexpensive, and–in the case of cold plasma–capable of significantly modifying the surface energy/features while minimizing negative impacts on the bulk properties of films or fabrics (including Non-Woven-Fabrics NWFs) that can result from high temperatures.…”

“…Therefore, plasma modification is a suitable, easy, cheap, and low environmental cost method to overcome these shortcomings. NWF-PP has been successfully activated and functionalized with cold atmospheric or low-pressure (or vacuum) plasma in order to improve polymer–polymer interactions, wettability, printability, adhesion feature, active molecules, or dyes bonding/exhaustion [ 4 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Plasma treatment of PP surfaces has also been successfully used in bioconjugation to grow and produce microbial cellulose pellicles or to favor the polymerization of allylamine for the following applications in biomaterials [ 23 , 24 , 25 ].…”

“…Therefore, there are few or no works aimed at rating the effect of plasma treatment variables on the changes in surface chemical structure or discussing the results from detailed analytical investigations of achieved functionalities, their distribution on the surface, and their evolution over time. Some data concerning the XPS characterization [ 4 , 14 , 16 , 21 , 22 , 28 , 32 ] elucidate the possible structure of functional groups deriving from oxygen and/or nitrogen addition, roughly confirmed by ATR-FTIR spectra analysis [ 5 , 14 , 19 , 33 ] and with some insights in their stability [ 13 , 15 , 17 ]. SEM microscopy is generally used to highlight the surface morphological variations of fibers following the various treatments [ 3 , 20 , 27 , 29 , 34 ].…”

Plasma Modification of Carbon Coating Produced by RF CVD on Oxidized NiTi Shape Memory Alloy under Glow-Discharge Conditions

“…Plasma treatments, including argon [21], oxygen [21,22,24], and sulfur hexafluoride [25] plasma, are used to modify the chemical state of the outer zones of the coatings, thus affecting its properties such as wettability, surface topography [21], and other mechanical [17] or electrical properties [23]. In addition, other materials such as polymers [25][26][27] have been recently modified using the possibility of simple one-step plasma treatments and obtained promising properties such as superhydrophilicity [26] or increased adhesion and uniformity of the coatings [27]). The production of a-C:N:H coatings on TiO 2 oxide layers made under glow-discharge conditions is beneficial due to the enhanced adhesion of the coatings to an oxidized NiTi substrate [28].…”