Adhesion Properties and Stability of Polar Polymers Treated by Air Atmospheric Pressure Plasma.

This study continues the discussion on the surface modification of polymers using an atmospheric pressure plasma (APP) reactor in air. These results complement prior research focusing on nonpolar polymers. Polymers, such as polyethylene terephthalate, polyetheretherketone, and polymethyl methacrylate, containing structurally bonded oxygen are studied, representing a range of properties such as oxygen content, crystalline/amorphous structure, polarity, functionality, and aliphatic/aromatic structure. APP induces superior wetting properties on the hydrophilic polymer surfaces with rapid and uniform modification within 0.5 s of exposure. The amorphous structures undergo additional modification for longer exposure. Moreover, the aliphatic chain structures require longer plasma exposure to reach surface modification equilibrium. The polar polymers reach a limit level of modification corresponding to a minimum water contact angle of about 50°. The surface polarity increases on average by a factor of approximately two. The equilibrium values of the adhesion work attained after post-processing recovery fall within a limited range of about 100-120 mJ/m2. The enhancement of surface functionality through the creation of oxidized groups primarily depends on the initial oxygen content and reaches a limit of about 40 at.% oxygen. The surface properties of the treated polar surfaces exhibit good stability, comparable to that of the previously tested nonpolar polymers.

Stable Surface Modification by Cold Atmospheric-Pressure Plasma: Comparative Study on Cellulose-Based and Synthetic Polymers.

This study's aim is a comparison of the plasma-induced effects on polymers exposed in helium and argon gaseous environments in a pulsed dielectric barrier discharge at atmospheric pressure. Cellulose-based and synthetic polymers are tested with regard to a range of parameters, such as wettability, adhesion, surface energy and polarity, the oxygen amount in their structure, and surface morphology. The surface properties are analyzed by contact angle measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy images. The results point to the efficient and remarkably stable modifications of the plasma-exposed surfaces, such as their enhanced adhesion, surface energy, and oxygen incorporation. Additionally, plasma provides significant oxygen uptake in cellulose-based materials that bear already prior to treatment a high amount of oxygen in their structure. The comparison between the properties of the non-permeable, homogeneous, smooth-surface synthetic polymer and those of the loosely packed, porous, heterogeneous cellulose-based polymers points to the different rates of plasma-induced modification, whereby a progressive alteration of cellulosic surface properties over much larger ranges of exposure durations is noted. Present experimental conditions ensure mild treatments on such sensitive material, such as paper, and this is without alterations of the surface morphology and the physical degradation of the material over a large range of treatment duration.

Adhesion Properties and Stability of Non-Polar Polymers Treated by Air Atmospheric-Pressure Plasma.

Atmospheric-pressure plasma (APP) has advantages for enhancing the adhesion of polymers and has to provide uniform, efficient treatment, which also limits the recovery effect of treated surfaces. This study investigates the effects of APP treatment on polymers that have no oxygen bonded in their structure and varying crystallinity, aiming to assess the maximum level of modification and the post-treatment stability of non-polar polymers based on their initial structure parameters, including the crystalline-amorphous structure. An APP reactor simulating continuous processing operating in air is employed, and the polymers are analyzed using contact angle measurement, XPS, AFM, and XRD. APP treatment significantly enhances the hydrophilic character of the polymers, with semicrystalline polymers exhibiting adhesion work values of approximately 105 mJ/m2 and 110 mJ/m2 for 0.5 s and 1.0 s exposure, respectively, while amorphous polymers reach approximately 128 mJ/m2. The maximum average oxygen uptake is around 30%. Short treatment times induce the roughening of the semicrystalline polymer surfaces, while the amorphous polymer surfaces become smoother. The polymers exhibit a limit to their modification level, with 0.5 s exposure being optimal for significant surface property changes. The treated surfaces remain remarkably stable, with the contact angle only reverting by a few degrees toward that of the untreated state.

Control of the blood-polymer interface by plasma treatment.

Plasma that is generated using dielectric barrier discharge is used to modify the surface properties of polymers used in medicine, at atmospheric pressure. Treatments are performed on films of polyamide-6, high density polyethylene, polymethylmetacrylate, and polytetrafluorethylene, selected for their medical applications. The plasma treatment conditions are discussed, in relation with relevant parameters for the adhesion properties, like the surface energy components, interfacial tension, surface topography, structural changes, and chemical composition. The interface properties are analyzed using the most important fluids implicated in the interfacial events related to the coagulation process at the interface of blood-polymer surface, respectively, water, whole blood, fibrinogen, and albumin. The physical and chemical modification of the surface is theoretically favorable to the interaction of the polymer with the blood and its components, by means of interfacial tension reduction, polarity increase, cleaning, ordering of molecular chains, functionalization, and stabilization effects.

Impact of silicone-based block copolymer surfactants on the surface and bulk microscopic organization of a biodegradable polymer, poly(epsilon-caprolactone).

Two amphiphilic AB block copolymers, containing a highly compatible poly(epsilon-caprolactone) (PCL) block connected to a poly(dimethylsiloxane) (PDMS) block having a low surface energy, are synthesized and characterized in terms of their dispersion in a presynthesized PCL matrix. X-ray photoelectron spectroscopy, contact angle measurements, atomic force microscopy, and optical microscopy are used to describe the evolution of the surface chemical composition, as well as the surface and bulk morphology of the PCL/copolymer blends as a function of the nature and weight surface free energy and the dispersion of the copolymers in the blends, leading to important modifications of the bulk and the surface morphology. These differences are interpreted in terms of the impact of the block copolymers on the semicrystalline polymer structure and related properties in the prospect of using the surfactants to improve the synthesis of PCL in supercritical CO(2).