Polymer Nanocomposite Surfaces Research Articles

Graphene-Based Antimicrobial Biomedical Surfaces.

Biomedical application of graphene derivatives have been intensively studied in last decade. With the exceptional structural, thermal, electrical, and mechanical properties, these materials have attracted immense attention of biomedical scientists to utilize graphene derivatives in biomedical devices to improve their performance or to achieve desired functions. Surfaces of graphene derivatives including graphite, graphene, graphene oxide and reduce graphene oxide have been demonstrated to pave an excellent platform for antimicrobial behavior, enhanced biocompatibility, tissue engineering, biosensors and drug delivery. This review focuses on the recent advancement in the research of biomedical devices with the coatings or highly structured polymer nanocomposite surfaces of graphene derivatives for antimicrobial activity and sterile surfaces comprising an entirely new class of antibacterial materials. Overall, we aim to highlight on the potential of these materials, current understanding and knowledge gap in the antimicrobial behavior and biocompatibility to be utilized of their coatings to prevent the cross infections.

The impacts of moisture and ultraviolet light on the degradation of graphene oxide/polymer nanocomposites

The extent to which hydrophilic GO nanofillers regulate polymer degradation during exposure to a combination of ultraviolet (UV) radiation and moisture is presently unknown. Accordingly, this study systematically evaluated the effect of GO on polymer degradability under both humid UV and dry UV conditions. Both GO accumulation at the polymer nanocomposite (PNC) surface and GO release following degradation were also investigated. Different mass loadings of GO were incorporated into waterborne polyurethane (WBPU), a commonly used exterior coating, and the resulting GO/WBPU nanocomposites were exposed to precisely controlled accelerated weathering conditions using the NIST Simulated Photodegradation via High Energy Radiant Exposure (SPHERE) device. Thickness loss and infrared spectroscopy measurements indicated GO slightly improved the durability of WBPU under dry UV conditions but not under humid UV conditions. Raman spectroscopy, scanning electron microscopy, and atomic force microscopy modulus measurements indicated that GO accumulation occurred at and near the PNC surface under both conditions but to a more rapid extent under humid UV conditions. Minimal GO release occurred under dry UV conditions as measured with Raman spectroscopy of aqueous run-off from a simulated rain spray applied to degraded PNCs. In contrast, PNC surface transformations under humid UV conditions suggested that GO release occurred.

Analysis of topographical parameters and interfacial interaction of zinc oxide reinforced poly (vinyl alcohol-g-acrylonitrile) nanocomposite film surfaces using atomic force microscopy

Motivated by the significance of surface morphology and topography of polymer nanocomposite surfaces, the present investigation was undertaken to design zinc oxide reinforced nanocomposites of poly(vinyl alcohol)-g-poly(acrylonitrile) and explore their morphological and topographical features. The grafted polymer matrix was prepared by a free radical polymerization method and zinc oxide nanoparticles were impregnated by adopting a simple sequential dipping method that involves alternate dipping of grafted polymer film in the alkali and the metal ions solutions, respectively to allow in situ precipitation of zinc oxide nanoparticles inside the polymer matrix. The as designed nanocomposite films were investigated for their morphology and topography by the atomic force microscopy (AFM) and transmission electron microscopy techniques. Various roughness parameters were calculated and a correlation was established between the morphology, topography and chemical composition of the nanocomposites. Furthermore, the surface compositional analysis was evaluated by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) to confirm the results since there usually remains a difference between the nominal and actual concentration of the prepared sample.

Self-cleaning and wear-resistant polymer nanocomposite surfaces

Superhydrophobic self-cleaning and wear-resistant nanocomposite surfaces were produced by mimicking the hierarchical structure of the lotus leaf using a combination of rapid self-assembly and a UV nano-imprint lithography (UVNIL) process with a silicone master. Two different acrylate formulations containing acrylated silica nanoparticles and an acrylated silicone surfactant were used. The presence of the silicone master did not suppress the spontaneous migration of the surfactant to the polymer surface, which increased its hydrophobic character. Adding acrylated silica particles considerably increased the viscosity of the acrylate suspensions and led to a shear-thinning behavior. However the particles did not prevent the fast migration process of the surfactant and further increased the hydrophobicity of the material, due to increased nanoscale roughness of the nanocomposite surface. The largest increase of hydrophobicity was achieved for the UVNIL printed lotus surfaces using the acrylate formulation with lowest viscosity. These surfaces became superhydrophobic for the highest investigated concentration of silica. These nanocomposite lotus surfaces were, in addition, very hard with a microhardness above 400 MPa and particularly wear-resistant, and were self-cleaning with respect to hydrophobic contamination.

Structure and Friction Behavior of UHMWPE/Inorganic Nanoparticles

We investigated tribological properties and worn surfaces morphology of polymer nanocomposite (PNCs) based on ultrahigh-molecular-weight polyethylene and aluminum and silicon oxide and nitride nanoparticle (NP) fillers by several methods to establish wear mechanisms. Joint mechanical activation in a planetary mill was used for the PNC preparation. PNCs with Al2O3 showed the best wear resistance. Scanning electron microscopy suggests that worn surfaces of PNCs with different fillers had different wear mechanisms. IR-spectroscopy and EDS analysis showed that oxidation processes occurred during friction and wear. Oxides of aluminum and silicon might be catalysts of oxidation processes. Due to tribochemical processes, cross-linked structures were formed on the PNCs surfaces. Probably, these cross-linked structures provide increase of wear resistance.

Interactions of microorganisms with polymer nanocomposite surfaces containing oxidized carbon nanotubes.

In many environmental scenarios, the fate and impact of polymer nanocomposites (PNCs) that contain carbon nanotubes (CNT/PNCs) will be influenced by their interactions with microorganisms, with implications for antimicrobial properties and the long-term persistence of PNCs. Using oxidized single-wall (O-SWCNTs) and multi-wall CNTs (O-MWCNTs), we explored the influence that CNT loading (mass fraction≤0.1%-10%) and type have on the initial interactions of Pseudomonas aeruginosa with O-CNT/poly(vinyl alcohol) (PVOH) nanocomposites containing well-dispersed O-CNTs. LIVE/DEAD staining revealed that, despite oxidation, the inclusion of O-SWCNTs or O-MWCNTs caused PNC surfaces to exhibit antimicrobial properties. The fraction of living cells deposited on both O-SWCNT and O-MWCNT/PNC surfaces decreased exponentially with increasing CNT loading, with O-SWCNTs being approximately three times more cytotoxic on a % w/w basis. Although not every contact event between attached microorganisms and CNTs led to cell death, the cytotoxicity of the CNT/PNC surfaces scaled with the total contact area that existed between the microorganisms and CNTs. However, because the antimicrobial properties of CNT/PNC surfaces require direct CNT-microbe contact, dead cells were able to shield living cells from the cytotoxic effects of CNTs, allowing biofilm formation to occur on CNT/PNCs exposed to Pseudomonas aeruginosa for longer time periods.

Superhydrophobic TiO2–Polymer Nanocomposite Surface with UV-Induced Reversible Wettability and Self-Cleaning Properties

Multifunctional superhydrophobic nanocomposite surfaces based on photocatalytic materials, such as fluorosilane modified TiO2, have generated significant research interest. However, there are two challenges to forming such multifunctional surfaces with stable superhydrophobic properties: the photocatalytic oxidation of the hydrophobic functional groups, which leads to the permanent loss of superhydrophobicity, as well as the photoinduced reversible hydrolysis of the catalytic particle surface. Herein, we report a simple and inexpensive template lamination method to fabricate multifunctional TiO2-high-density polyethylene (HDPE) nanocomposite surfaces exhibiting superhydrophobicity, UV-induced reversible wettability, and self-cleaning properties. The laminated surface possesses a hierarchical roughness spanning the micro- to nanoscale range. This was achieved by using a wire mesh template to emboss the HDPE surface creating an array of polymeric posts while partially embedding untreated TiO2 nanoparticles selectively into the top surface of these features. The surface exhibits excellent superhydrophobic properties immediately after lamination without any chemical surface modification to the TiO2 nanoparticles. Exposure to UV light causes the surface to become hydrophilic. This change in wettability can be reversed by heating the surface to restore superhydrophobicity. The effect of TiO2 nanoparticle surface coverage and chemical composition on the mechanism and magnitude of wettability changes was studied by EDX and XPS. In addition, the ability of the surface to shed impacting water droplets as well as the ability of such droplets to clean away particulate contaminants was demonstrated.

Investigation of surface properties of plasma-modified polyamide 6 and polyamide 6/layered silicate nanocomposites

Polyamide 6 and polyamide 6/layered silicate nanocomposites were treated by oxygen plasma and the resulting surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared-attenuated total reflection (FTIR-ATR). The surface properties were also analyzed by water contact angle measurements and Taber abrasion test. It is found that plasma treatment had different effects on the surfaces of the homopolymer and the polymer nanocomposites. Furthermore, both plasma duration and nanoclay content affect the contact angle and degree of abrasion resistance. In pure polyamide 6, plasma treatment caused the surface to be highly hydrophilic due to the formation of cyclic cis-amide species. Polymer nanocomposites treated with plasma also became more hydrophilic due to oxidation and enrichment of clay at the surface. The abrasion resistance of pure polyamide 6 was increased after exposure to plasma. This is attributed to cross-linking of polymer chains when exposed to plasma. For the polymer nanocomposites, an improvement in abrasion resistance was obtained in samples with low clay content when exposed to plasma for a short time. This is also due to cross-linking as well as the higher abrasion resistance of clay. However, longer exposure to plasma resulted in poorer abrasion resistance due to self-aggregation of clay particles which can be easily removed from the surface. A model was proposed to explain the effect of oxygen plasma on polymer nanocomposite surface.