Polymer System Based on Polyethylene Glycol and TFE Telomers for Producing Films with Switchable Wettability.

Today a lot of attention is paid to the formation of thermosensitive systems for biomedical and industrial applications. The development of new methods for synthesis of such systems is a dynamically developing direction in chemistry and materials science. In this regard, this paper presents results of the studies of a new synthesized supramolecular polymer system based on polyethylene glycol and tetrafluoroethylene telomers. The films formed from the polymer substance have the property of switching wettability depending on temperature after heating activation. It has been established that the wettability changes at 60 °C. The contact angle of activated hydrophobic polymer film reaches 143°. Additionally, the system exhibits its properties regardless of the pH of the environment. Based on data obtained by the methods of infrared and x-ray photoelectron spectroscopy, differential thermal analysis and thermal analysis in conjunction with wettability and morphology, a model of the behavior of molecules in a polymer system was built that ensures switching of the hydrophilic/hydrophobic surface state. The resulting polymer system, as well as films based on it, can be used in targeted drug delivery, implantation surgery, as sensors, etc.

Composite Coatings of AMg3 Alloy Formed by a Combination of Plasma Electrolytic Oxidation and Fluoropolymer Spraying.

This paper presents the results of an investigation of the changes in the corrosion, wear resistance, and wettability of composite coatings formed on the AMg3 alloy through plasma electrolytic oxidation (PEO) and subsequent spraying with an organofluorine polymer. The evaluation of the electrochemical properties of the composite layers revealed a decrease in the corrosion current density compared with the PEO coating (from 3.8 × 10-8 to 3.1 × 10-11 A/cm2). The analysis of the wear resistance of composite coatings established that the application of this type of coating reduced the wear of the samples by two orders of magnitude when compared with the PEO layer. Using the contact-angle measurement, it was found that with an increase in the number of polymer spray applications, the wettability of coatings decreased, so the contact angle for the composite coating with triple fluoropolymer application increased by 134.3° compared to the base PEO coating.

Features of Composite Layers Created Using an Aqueous Suspension of a Fluoropolymer.

This paper presents a method for the formation of composite-polymer-containing coatings on MA8 Mg alloy by plasma electrolytic oxidation (PEO), followed by the deposition of a fluoropolymer from an aqueous suspension of superdispersed polytetrafluoroethylene. The Scanning Electron Microscope(SEM), Energy Dispersive Spectroscopy(EDS), and X-ray Diffraction(XRD) analyses established morphological features as well as elemental and phase composition of composite coatings. The fact that the pores are filled with a fluoropolymer has been experimentally confirmed. An assessment of the corrosion properties of formed composite coatings revealed a decrease in the corrosion current density by more than four orders of magnitude in comparison with the base PEO layer. The highest resistance to the damaging effects of a corrosive environment, according to the results of long-term exposure tests, was demonstrated by coatings after three treatments with polytetrafluoroethylene. The obtained polymer-containing coatings have antifriction properties, reducing the wear of the coatings by more than 27-fold in comparison with the base PEO layer. It was revealed that composite coatings have superhydrophobic properties: the value of the contact angle reaches 154°, and the hysteresis of the contact angle is less than 10°.

PEO Coatings Modified with Halloysite Nanotubes: Composition, Properties, and Release Performance.

In this work, the properties of the coatings formed on the Mg-Mn-Ce alloy by plasma electrolytic oxidation (PEO) in electrolytes containing halloysite nanotubes (HNTs) were investigated. The incorporation of halloysite nanotubes into the PEO coatings improved their mechanical characteristics, increased thickness, and corrosion resistance. The studied layers reduced corrosion current density by more than two times in comparison with the base PEO layer without HNTs (from 1.1 × 10-7 A/cm2 to 4.9 × 10-8 A/cm2). The presence of halloysite nanotubes and products of their dihydroxylation that were formed under the PEO conditions had a positive impact on the microhardness of the obtained layers (this parameter increased from 4.5 ± 0.4 GPa to 7.3 ± 0.5 GPa). In comparison with the base PEO layer, coatings containing halloysite nanotubes exhibited sustained release and higher adsorption capacity regarding caffeine.

Icephobic Performance of Combined Fluorine-Containing Composite Layers on Al-Mg-Mn-Si Alloy Surface.

This paper presents the results of an evaluation of anti-icing properties of samples obtained by plasma electrolytic oxidation (PEO) with a subsequent application of superdispersed polytetrafluoroethylene (SPTFE) and polyvinylidenefluoride (PVDF). A combined treatment of the samples with SPTFE and PVDF is also presented. It is revealed that impregnation of a PEO layer with fluoropolymer materials leads to a significant increase in surface relief uniformity. Combined PVDF-SPFTE layers with a ratio of PVDF to SPTFE of 1:4 reveal the best electrochemical characteristics, hydrophobicity and icephobic properties among all of the studied samples. It is shown that the decrease in corrosion current density Ic for PVDF-SPFTE coatings is higher by more than five orders of magnitude in comparison with uncoated aluminum alloy. The contact angle for PVDF-SPFTE coatings attain 160.5°, which allows us to classify the coating as superhydrophobic with promising anti-icing performance. A treatment of a PEO layer with PVDF-SPFTE leads to a decrease in ice adhesion strength by 22.1 times compared to an untreated PEO coating.

Bioactive Coatings Formed on Titanium by Plasma Electrolytic Oxidation: Composition and Properties.

Bioactive coatings on VT1-0 commercially pure titanium were formed by the plasma electrolytic oxidation (PEO). A study of the morphological features of coatings was carried out using scanning electron microscopy. A composition of formed coatings was investigated using energy-dispersive spectroscopy and X-ray diffractometry analysis. It was shown that PEO-coatings have calcium phosphate in their composition, which increases the bioactivity of the surface layer. Electrochemical properties of the samples were studied by potentiondynamic polarization and electrochemical impedance spectroscopy in different physiological media: simulated body fluid and minimum essential medium. The data of electrochemical studies indicate more than 15 times decrease in the corrosion current density for the sample with coating (5.0 × 10-9 A/cm2) as compared to the bare titanium (7.7 × 10-8 A/cm2). The formed PEO-layers have elastoplastic properties close to human bone (12-30 GPa) and a lower friction coefficient in comparison with bare metal. The wettability of PEO-layers increased. The contact angle for formed coatings reduced by more than 60° in comparison with bare metal (from 73° for titanium to 8° for PEO-coating). Such an increase in surface hydrophilicity contributes to the greater biocompatibility of the formed coating in comparison with commercially pure titanium. PEO can be prospective as a method for improving titanium surface bioactivity.

Atmospheric and Marine Corrosion of PEO and Composite Coatings Obtained on Al-Cu-Mg Aluminum Alloy.

Wrought Al-Cu-Mg aluminum alloy (D16) was treated by bipolar plasma electrolytic oxidation to create a base plasma electrolytic oxidation (PEO)-coating with corrosion protection and mechanical properties superior to bare alloy's natural oxide layer. Additional protection was provided by the application of polymer, thus creating a composite coating. Electrochemical and scratch tests, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction studies were performed. Degradation of coatings in the marine atmosphere and seawater was evaluated. The composite polymer-containing coating provided better corrosion protection of aluminum alloy compared to the PEO-coating, although seawater affected both. During the atmospheric exposure, the PEO-coating provided reasonably good protection, and the composite coating showed excellent performance.