Molecular dynamics study of the swelling and osmotic properties of compact nanogel particles

Owing to their great importance in materials science and other fields, we investigate the solution and osmotic properties of uncharged compact nanogel particles over a wide range of solvent quality and particle concentration by molecular dynamics (MD) simulations. We characterize the osmotic pressure by estimating the second and third virial coefficients, and by extension, we identify the θ-point where the second virial coefficient vanishes. Calculations of the structure factor indicate that these particles are similar to macrogels in that the particle-like scattering profile disappears at moderate concentrations. We also find that improving the solvent quality enhances the spatial segmental uniformity, while significant heterogeneous structure arises near the θ-point. Well below the θ-point where the second osmotic virial coefficient vanishes, these heterogeneous structures become less prevalent as the particles tend to collapse. We also investigate the degree of swelling and structure of compact nanogel particles with a variable excluded volume interaction and gel particle concentration. The osmotic modulus and the scaling exponents in good and θ-point conditions of these gels are characteristic of interacting randomly branched polymers, i.e., "lattice animals".

Magnetic Ionic Liquid Nanocatalyst to Improve Mechanical and Thermal Properties of Epoxy Nanocomposites

New magnetic imidazolium ionic liquid (IIL) was synthesized to improve the curing, mechanical, and thermal characteristics of the epoxy/polyamine system. In this respect, 2-(4-minophenyl)-1.3-bis(triethoxysilyl)-1H-imidazol-3-ium acetate as IIL was synthesized and characterized by different spectroscopy tools. The IIL was used as capping to prepare Fe₃O₄ nanoparticles (NPs) as new Fe₃O₄-IIL NPs. The thermal stability, morphology, crystal lattice structures, and magnetic properties were evaluated to confirm the formation of uniform, thermal, stable, and superparamagnetic Fe₃O₄-IIL NPs. The prepared Fe₃O₄-IIL NPs were mixed with an epoxy/polyamine system to improve the curing, thermal, and mechanical properties of epoxy through chemical reactions. The dynamic mechanical analyzer and differential scanning calorimeter were used to investigate the flexibility and storage modulus of the cured epoxy/polyamine system in the absence and presence of Fe₃O₄-IIL NPs. The atomic force microscope and scanning electron microscope were used to evaluate the dispersion and embedding of Fe₃O₄-IIL NPs into epoxy matrix. The thermal, mechanical, and surface morphologies data confirmed that the incorporation of Fe₃O₄-IIL NPs using 3 wt. % during the curing of an epoxy/polyamine system produces superior epoxy films without cracks, holes, and NPs agglomeration.

Synthesis of calcium carbonate microcapsules as self-healing containers

Contemporary studies of self-healing polymer composites are based on microcapsules synthesized using synthetic and toxic polymers, biopolymers, etc. via methods such as in situ polymerization, electrospraying, and air atomization. Herein, we synthesized a healing agent, epoxy (EPX) encapsulated calcium carbonate (CC) microcapsules, which was used to prepare self-healing EPX composites as a protective coating for metals. The CC microcapsules were synthesized using two facile methods, namely, the soft-template method (STM) and the in situ emulsion method (EM). Microcapsules prepared using the STM (ST-CC) were synthesized using sodium dodecyl sulphate (SDS) surfactant micelles as the soft-template, while the microcapsules prepared using the EM (EM-CC) were synthesized in an oil-in-water (O/W) in situ emulsion. These prepared CC microcapsules were characterized using light microscopy (LMC), field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and thermogravimetric analysis (TGA). The synthesized ST-CC microcapsules were spherical in shape, with an average diameter of 2.5 μm and an average shell wall thickness of 650 nm, while EM-CC microcapsules had a near-spherical shape with an average diameter of 3.4 μm and an average shell wall thickness of 880 nm. The ST-CC capsules exhibited flake-like rough surfaces while EM-CC capsules showed smooth bulgy surfaces. The loading capacity of ST-CC and EM-CC microcapsules were estimated using TGA and found to be 11% and 36%, respectively. The FTIR and NMR spectra confirmed the EPX encapsulation and the unreactive nature of the loaded EPX with the inner walls of CC microcapsules. The synthesized CC microcapsules were further incorporated into an EPX matrix to prepare composite coatings with 10 (w/w%), 20 (w/w%), and 50 (w/w%) capsule loadings. The prepared EPX composite coatings were scratched and observed using FE-SEM and LMC to evaluate the release of encapsulated EPX inside the CC capsules, which is analogous to the healing behaviour. Moreover, EPX composite coatings with 20 (w/w%) and 50 (w/w%) of ST-CC showed better healing performances. Thus, it was observed that ST-CC microcapsules outperformed EM-CC. Additionally, the EPX/CC coatings showed remarkable self-healing properties by closing the gaps of the scratch surfaces. Thus, these formaldehyde-free, biocompatible, biodegradable, and non-toxic CC based EPX composite coatings hold great potential to be used as a protective coating for metal substrates. Primary results detected significant corrosion retardancy due to the self-healing coatings under an accelerated corrosion process, which was performed with a salt spray test.

Healing agent, epoxy encapsulated calcium carbonate microcapsules were prepared using a facile method as a self-healing composite for protective metal coatings.

Effect of Montmorillonite Nanogel Composite Fillers on the Protection Performance of Epoxy Coatings on Steel Pipelines

Montmorillonite (MMT) clay mineral is widely used as filler for several organic coatings. Its activity is increased by exfoliation via chemical modification to produce nanomaterials. In the present work, the modification of MMT to form nanogel composites is proposed to increase the dispersion of MMT into epoxy matrices used to fill cracks and holes produced by the curing exotherms of epoxy resins. The dispersion of MMT in epoxy improved both the mechanical and anti-corrosion performance of epoxy coatings in aggressive marine environments. In this respect, the MMT surfaces were chemically modified with different types of 2-acrylamido-2-methyl propane sulfonic acid (AMPS) nanogels using a surfactant-free dispersion polymerization technique. The effect of the chemical structure, nanogel content and the interaction with MMT surfaces on the surface morphology, surface charges and dispersion in the epoxy matrix were investigated for use as nano-filler for epoxy coatings. The modified MMT nanogel epoxy composites showed excellent resistance to mechanical damage and salt spray resistance up to 1000 h. The interaction of MMT nanogel composites with the epoxy matrix and good response of AMPS nanogel to sea water improve their ability to act as self-healing materials for epoxy coatings for steel.