Electroassisted Functionalization of Nitinol Surface, a Powerful Strategy for Polymer Coating through Controlled Radical Surface Initiation

Coating Nitinol (NiTi) surfaces with a polymer layer has become very appealing in the past few years owing to its increased attraction in the biomedical field. Although its intrinsic properties helped ensure its popularity, its extensive implementation is still hampered by its nickel inclusion, making it sensitive to pitting corrosion and therefore leading to the release of carcinogenic Ni²⁺ ions. Among all recent ways to modify NiTi surfaces, elaboration of self-assembled monolayers is of great interest as their high order confers a reinforcement of the metal surface corrosion resistance and brings new functionalities to the metal for postmodification processes. In this work, we compare the electroassisted and thermally assisted self-assembling of 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) to the classical immersion process on NiTi surfaces initially submitted to a hydrothermal treatment. Among all tested conditions, the electroassisted grafting of BUPA at room temperature appears to be the most promising alternative, as it allows grafting in very short times (5–10 min), thus preventing its degradation. The thus-formed layer has been proven to be sufficient to enable the surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-(dimethylamino)­ethyl methacrylate

Plasma Treatment of Metal Oxide Nanoparticles: Development of Core–Shell Structures for a Better and Similar Dispersibility

Low-pressure plasma polymerization of cyclopropylamine was employed for the surface functionalization of commercial ZnO, Al₂O₃, and ZrO₂ nanoparticles in a homemade hollow cathode plasma reactor. The analysis of the modified nanoparticles by X-ray photoelectron spectroscopy (XPS) revealed the incorporation of reactive functional groups such as primary and secondary amines, which was confirmed by Fourier transform infrared spectroscopy (FTIR). The raw and the plasma functionalized nanoparticles were evaluated in terms of dispersibility. Application of Hansen solubility parameters (HSP) theory showed that the efficient plasma polymerization that led to the deposition of an approximately 5 nm thick plasma polymer film, as determined by transmission electron microscopy (TEM), causes a similar shift toward the Hansen solubility space for the functionalized nanoparticles and changes their physicochemical affinity within selected solvents, regardless of the kind of nanoparticles used. Hence, a combined exploitation of nanoparticles having different cores is feasible in applications such as nanocomposites and bioapplications having certain reactivity after grafting an amine-based plasma polymer film that allows achieving a similar dispersibility