No abstract

The goal of this work was to study the wettability of the recycled polyvinylchloride (PVC) and polyethylene terephthalate (PET) surface, in which was used the technique of Plasma immersion (PI), by means of ionic bombardment using the gas Sulfur Hexafluoride (SF6) with total pressures down to 100 torr. The substrates were confined in a low vacuum reactor, and gas was excited by a radiofrequency discharge source, RF: (13.56 MHz) applied to the lower electrode (sample holder), coupled to a match in box. The surface wettability result of these polymers via "contact angle, ϴ", were compared with parallel studies in the literature. In this case, the technique of Infrared Absorption Spectroscopy (FTIR) was applied in order to analyze the possible physico-chemical changes in the surface of the polymers in the presence of an organic film of Isopropanol, SF 6 , whose values of ϴ were lower than the untreated material, even in the fluorinated atmosphere.Therefore, the parameters pressure, time or discharge power of RF were varied, In all cases, moderate to high fluorine is considered, with contact angles close to 120º are inferior to a similar treatment in literature, in which it was applied, a cooling prototype of the sampled electrode throughout the process; condition that resulted in PVC, ϴ ~ 156º (surface with higher degree of fluorine); and PET in turn reached ϴ ~ 140 °.

Because of its excellent properties, carbon steel is a material widely used in several sectors. However, it is easily corroded when exposed to the environment. Seeking to remedy this problem, the possibility of coating carbon steel with SiO x /SiO x C y H z films generated by deposition and oxidation in low-pressure plasmas was investigated. Specifically, the effects of excitation power of the oxidation plasma on layer thickness, chemical structure, elemental composition, and barrier properties of the obtained coatings were investigated. The coating of the steel with the SiO x C y H z film, generated by plasma in an atmosphere of hexamethyldisiloxane (HMDSO), increased the total resistance to the passage of electric current, measured by electrochemical impedance spectroscopy. However, under the condition of moderate power oxidation (50 W), the results point to the creation of a bilayer system with high resistance to electrochemical attack compared to the SiO x C y H z film, even though its thickness is less than this.

Surface modification techniques based on the grafting of chemical functional groups and immobilization of bioactive molecules have been used to improve biocompatibility and clinical performance of bioabsorbable scaffolds in tissue engineering and medicine regenerative applications. This study aimed at developing and characterizing a biomimetic surface to stimulate bone regeneration by a simple and low-cost method of surface biofunctionalization of the poly (L-co-D,L lactic acid)-PLDLA scaffolds. The method was obtained by grafting reaction of carboxyl groups (-COOH) on their surface via acrylic acid (AAc) polymerization process, followed by immobilization of collagen type I (Col). Such approach resulted in a surface morphology markedly modified after treatment, with increase of pores and roughness on PLDLA-AAc surfaces and a network of fibrillar collagen deposition in nonspecific areas of PLDLA-Col surfaces. The cytocompatibility of collagen-immobilized scaffolds was significantly improved in terms of cellular adhesion, proliferation, collagen synthesis and maintenance of osteoblast-like phenotype, indicating, therefore, the fundamental role of collagen protein over the biological interactions that occur by bio-recognition mimetic mechanisms at biomaterials interface. These results indicate that the surface modification method used here may be useful as a strategy to develop biofunctional scaffolds, which provide a more successful clinical application of biomaterials in the tissue engineering field.

In this work, thin polymer films were prepared from acetylene and argon radiofrequency (13.56 MHz, 80 W) glow discharges. Post-deposition treatment was performed by plasma immersion ion implantation in nitrogen or helium glow discharges (13.56 MHz, 70 W). In these cases, samples were biased with 25 kV negative pulses. Exposure time to the bombardment plasma, t, ranged from 900 to 7200 s. Chemical composition of the film surfaces was investigated by X-ray Photoelectron Spectroscopy and the resistance to oxidation by the etching process, in reactive oxygen plasmas. Oxygen and nitrogen were detected in all the samples. While the concentration of the former continuously changed with t, that of N kept practically constant in small proportions. The film is predominantly formed by sp² states, but the proportion of sp³ hybridization slightly increased with t. The etching rate dropped under certain conditions of nitrogen bombardment whereas helium implantation has not significantly improved it. These results are ascribed to the crosslinking degree of the polymeric chains, ruled by the total amount of energy delivered to the film