Uniform distribution of graphene oxide sheets into a poly-vinylidene fluoride nanoparticle matrix through shear-driven aggregation

Exploring the material and dielectric properties of poly(vinylidene fluoride) composites incorporated with graphene and graphene oxide

This study focuses on enhancing the structural, thermal, and dielectric properties of poly(vinylidene fluoride) (PVDF) nanocomposites loaded with graphene oxide (GO) and graphene (G), synthesized via solution casting. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA), revealed significant enhancements due to the nanofillers. The crystallinity of PG composites increased to 60.39% from 49.21% in neat PVDF, transitioning from α to β phases, which is beneficial for high-performance electronics and energy storage. PG composites showed a dielectric constant (ε') of 10.50, higher than those of neat PVDF (ε' = 7.54) and PGO composites (ε' = 8.56). The dielectric loss (tan δ) for PG was low at 0.15, suitable for electronics. The AC conductivity of PG composites (2.22 × 10-7 S cm-1) was higher than those of neat PVDF (1.09 × 10-7 S cm-1) and PGO (1.65 × 10-7 S cm-1), enhancing their suitability for flexible electronics. Thermal stability assessments showed that PG composites had the highest degradation temperature at 471.04 °C, indicating improved thermal resistance. These enhancements are due to the effective dispersion and interaction of graphene-based nanofillers within the PVDF matrix. This study demonstrates that incorporating nanofillers into polymer composites significantly advances materials science by enhancing the dielectric properties for various industrial applications.

Superhydrophobic nanocomposite coatings with photoinitiated three-dimensional networks based on reactive graphene nanosheet-induced self-wrinkling patterned surfaces

HYPOTHESIS

Bionic superhydrophobicity including high contact angle, low sliding angle and nonstick property, combined with both strong pH and ultraviolet (UV) resistance, is difficult to simultaneously achieve for large-scale preparation of superhydrophobic surfaces by blending polymer with a nonreactive inorganic nanofiller.

EXPERIMENTS

A series of high pH and UV-irradiation-resistant superhydrophobic nanocomposite films were prepared through UV-light-assisted chemical cross-linking among ternary components under nitrogen protection. Ethoxylated bisphenol A diacrylate, 2-(perfluorooctyl) ethyl acrylate, reactive thiol-coupled graphene nanosheets and photoinitiator were evenly mixed, followed by UV-irradiation curing.

FINDINGS

Abundant 3D networks could be formed. A robust self-wrinkling surface morphology was formed due to a UV-curing-induced inner tension in the composites, 2D morphology-induced flexibility for graphene nanosheets and fluorine-bearing component-induced phase separation at the wetted surfaces. High roughness and use of the fluorine element endows the surfaces with superhydrophobicity and oleophobicity. A favorable nonstick performance was obtained. Superhydrophobicity could be maintained despite changing the film-forming substrate, pH of soaking solutions from 1 to 12, or use of a prolonged UV-irradiation time reaching 120 h. Therefore, both superhydrophobicity/oleophobicity and strong pH/UV resistance are finely balanced. This work might open up the way for large-scale fabrication of promising superhydrophobic surfaces.

Effect of SiO₂ Nanoparticles on the Performance of PVdF-HFP/Ionic Liquid Separator for Lithium-Ion Batteries

Safety concerns related to the use of potentially explosive, liquid organic electrolytes in commercial high-power lithium-ion batteries are constantly rising. One promising alternative is to use thermally stable ionic liquids (ILs) as conductive media, which are however, limited by low ionic conductivity at room temperature. This can be improved by adding fillers, such as silica or alumina nanoparticles (NPs), in the polymer matrix that hosts the IL. To maximize the effect of such NPs, they have to be uniformly dispersed in the matrix while keeping their size as small as possible. In this work, starting from a water dispersion of silica NPs, we present a novel method to incorporate silica NPs at the nanoscale level (<200 nm) into PVdF-HFP polymer clusters, which are then blended with the IL solution and hot-pressed to form separators suitable for battery applications. The effect of different amounts of silica in the polymer matrix on the ionic conductivity and cyclability of the separator is investigated. A membrane containing 10 wt.% of silica (with respect to the polymer) was shown to maximize the performance of the separator, with a room temperature ionic conductivity of of 1.22 mS cm - 1 . The assembled half-coin cell with LiFePO 4 and Li as the cathode and the anode exhibited a capacity retention of more than 80% at a current density of 2C and 60 ∘ C.

Generation of Polymer Nanocomposites through Shear-Driven Aggregation of Binary Colloids

Design of polymer nanocomposites has been an intense research topic in recent decades because hybrid nanomaterials are widely used in many fields. Throughout their development, there has often been a challenging issue how one can uniformly distribute nanoparticles (NPs) in a polymer matrix, avoiding their agglomeration. In this short review, we first introduce the theory of colloidal aggregation/gelation purely based on intense shear forces. Then, we illustrate a methodology for preparing polymer nanocomposites where the NPs (as fillers) are uniformly and randomly distributed inside a matrix of polymer NPs, based on intense shear-driven aggregation of binary colloids, without using any additives. Its feasibility has been demonstrated using two stable binary colloids composed of (1) poly-methyl methacrylate fillers and polystyrene NPs, and (2) graphene oxide sheets (fillers) and poly-vinylidene fluoride NPs. The mechanism leading to capturing and distribution of the fillers inside the polymer NP matrix has been illustrated, and the advantages of the proposed methodology compared with the other common methods are also discussed.