Natural deep eutectics
solvents (NADES), owing to their high solvation
capacity and nontoxicity, are actively being sought for many technological
applications. Herein, we report a series of novel NADES based on choline
chloride and plant-derived polyphenols. Most of the obtained phenolic
NADES have a wide liquid range and high thermal stability above 150
°C. Among them, small-sized polyphenols, like pyrogallol, vanillyl
alcohol, or gentisic acid, lead to low-viscosity liquids with ionic
conductivities in the order of 10
–3
S cm
–1
at room temperature. Interestingly, polyphenols possess valuable
properties as therapeutic agents, antioxidants, adhesives, or redox-active
compounds, among others. Thus, we evaluated the potential of these
novel NADES for two applications: bioadhesives and corrosion protection.
The mixture of choline chloride-vanillyl alcohol (2:3 mol ratio) and
gelatin resulted in a highly adhesive viscoelastic liquid (adhesive
stress ≈ 135 kPa), affording shear thinning behavior. Furthermore,
choline chloride-tannic acid (20:1) showed an extraordinary ability
to coordinate iron ions, reaching excellent corrosion inhibitive efficiencies
in mild steel protection.
Metal/polymer nanocomposites have attracted much attention in recent years due to their exceptional properties and wide range of potential applications. A key challenge to obtain these materials is to stabilize the metal nanoparticles in the matrix, avoiding uncontrolled aggregation processes driven by the high surface free energy of nanosized particles. Here, we investigate the aggregation mechanism of primary particles in gold−epoxy nanocomposites prepared via light-assisted in situ synthesis, under different irradiation conditions. The growth and aggregation of gold nanoparticles were monitored in situ by time-resolved small-angle X-ray scattering experiments, whereas spectroscopic measurements were performed to interpret how matrix polymerization influences the aggregation process. It was found that light intensity has a greater influence on the reduction rate than on the polymerization rate. Under irradiation, gold nanostructures evolve through five time-defined stages: nucleimass fractalssurface fractalsspherical nanoparticlesaggregates. If the maximum in the polymerization rate is reached before the aggregation step, individual primary nanoparticles will be preserved in the polymer matrix due to diffusional constraints imposed by the reaction medium. Because the light intensity has a different influence on the reduction rate than on the polymerization rate, this parameter can be used as a versatile tool to avoid aggregation of gold nanoparticles into the polymer matrix.
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