High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates

In Situ Synthesis of Exfoliated Ni(OH)2 Nanosheets and AgNPs-Embedded Functionalized Polyindole-Based Trinary Hybrid Microspheres: A Z-Scheme Photocatalyst for the Sunlight-Driven Degradation of Organic Pollutants with Enhanced Antibacterial Efficacy

Advancing a facile one-pot synthetic approach for the fabrication of a hybrid heterojunction photocatalyst remains a significant challenge in research pursuits. Herein, a microsphere-like trinary hybrid nanocomposite has been synthesized (NH/PIn/MAA/Ag). It comprises exfoliated single- and a few-layered Ni(OH)2 (NH nanosheets), mercaptoacetate-functionalized polyindole (PIn/MAA), and Ag nanoparticles (AgNPs) through an in situ approach. The formation mechanism is based on the exfoliation of stacked Ni(OH)2 multilayers [i.e., Ni(OH)2 microflowers] and stabilization of NH nanosheets through host-guest formation of PIn/MAA, followed by the adsorption-reduction of Ag+ ions in a one-pot reaction at low temperature. Surface morphological analyses of hybrid nanocomposite microspheres have exhibited that highly dense Ni(OH)2 microflowers have been transformed into low-density layered forms (NH nanosheets) within the polymeric platform (PIn/MAA) with deposited AgNPs. An interfacial heterojunction has been developed between the components in the depletion region, leading to an improvement in photocatalytic efficiency through a synergistic effect over the components for charge separation and transfer through the heterojunction interface via solid-state mediator Ag-based Z-scheme charge transfer dynamics. The superior photocatalytic degradation of tetracycline (98.2%) by trinary hybrid microspheres can be attributed to the deteriorated recombination rate of electron-hole pairs with reduced charge transfer resistance of the heterojunction in the photocatalyst, as obvious from photoluminescence, electrochemical impedance spectroscopy, chronoamperometry, and time-resolved photoluminescence (TRPL) analyses. Moreover, the antibacterial properties of microspheres against Bacillus pumilus (Gram-positive) and Escherichia coli (Gram-negative) bacteria have validated their potential as promising materials for the overall purification of aquatic systems.

From the Lab to the Field: Organic Materials for Industrial Applications and Environmental Remediation

Many new developments for different industries have their origin in basic science. In recent years, this trend has gained attention due to the increasing interaction between academic science and industry. This article presents some rational materials for chemical modifications that were developed by the basic science, then transferred to the productive sector. Conducting hydrophobic coatings for aerospace applications, hydrogels for the oil and gas industry, as well as polymers for removal of heavy metal, were some of the topics approached in the lab to solve industrial problems. Many times, nature is a great source of inspiration to produce new materials. In this sense, superhydrophobicity and superhydrophilicity (concepts closely related to our everyday life) were the bioinspiration for the development of membranes. These membranes were able to separate hydrocarbons and water, which found application in the treatment of subterranean water for the oil and gas industry.

Surface Sizing Treated MWCNTs and Its Effect on the Wettability, Interfacial Interaction and Flexural Properties of MWCNT/Epoxy Nanocomposites

A surface-sizing technique was offered to take full advantage of multi-walled carbon nanotubes (MWCNTs) and epoxy resins. Two surface-sizing treated MWCNTs were obtained through a ball-milling treatment of amino-functionalized MWCNTs (MWCNT-NH₂) with n-butyl glycidylether (BuGE) and benzyl glycidylether (BeGE). These were referred to as MWCNT-BuGE and MWCNT-BeGE. The results indicated that the surface sizing effectively enhanced wettability, dispersibility of MWCNTs in the epoxy resin. These ameliorating effects, along with improved interfacial interaction between MWCNT-BeGE containing benzene rings and the epoxy matrix, which can offer a more efficient local load-transfer from matrix to MWCNTs, as observed by a higher G-band shift in Raman spectrum under bending loads than that of MWCNT-BuGE reinforced ones. Correspondingly, MWCNT-BeGE/epoxy nanocomposites exhibited increasing flexural strength and modulus of 22.9% and 37.8% respectively compared with the neat epoxy, and 7.3% and 7.7% respectively compared with MWCNT-BuGE/epoxy nanocomposites with the same MWCNT content.

Carbon nanotubes within polymer matrix can synergistically enhance mechanical energy dissipation

Safe operation and health of structures relies on their ability to effectively dissipate undesired vibrations, which could otherwise significantly reduce the life-time of a structure due to fatigue loads or large deformations. To address this issue, nanoscale fillers, such as carbon nanotubes (CNTs), have been utilized to dissipate mechanical energy in polymer-based nanocomposites through filler-matrix interfacial friction by benefitting from their large interface area with the matrix. In this manuscript, for the first time, we experimentally investigate the effect of CNT alignment with respect to reach other and their orientation with respect to the loading direction on vibrational damping in nanocomposites. The matrix was polystyrene (PS). A new technique was developed to fabricate PS-CNT nanocomposites which allows for controlling the angle of CNTs with respect to the far-field loading direction (misalignment angle). Samples were subjected to dynamic mechanical analysis, and the damping of the samples were measured as the ratio of the loss to storage moduli versus CNT misalignment angle. Our results defied a notion that randomly oriented CNT nanocomposites can be approximated as a combination of matrix-CNT representative volume elements with randomly aligned CNTs. Instead, our results points to major contributions of stress concentration induced by each CNT in the matrix in proximity of other CNTs on vibrational damping. The stress fields around CNTs in PS-CNT nanocomposites were studied via finite element analysis. Our findings provide significant new insights not only on vibrational damping nanocomposites, but also on their failure modes and toughness, in relation to interface phenomena.

Simultaneously improving the mechanical and electrical properties of poly(vinyl alcohol) composites by high-quality graphitic nanoribbons

Although carbon nanotubes (CNTs) have shown great potential for enhancing the performance of polymer matrices, their reinforcement role still needs to be further improved. Here we implement a structural modification of multi-walled CNTs (MWCNTs) to fully utilize their fascinating mechanical and electrical properties via longitudinal splitting of MWCNTs into graphitic nanoribbons (GNRs). This nanofiller design strategy is advantageous for surface functionalization, strong interface adhesion as well as boosting the interfacial contact area without losing the intrinsic graphitic structure. The obtained GNRs have planar geometry, quasi-1D structure and high-quality crystallinity, which outperforms their tubular counterparts, delivering a superior load-bearing efficiency and conductive network for realizing a synchronous improvement of the mechanical and electrical properties of a PVA-based composite. Compared to PVA/CNTs, the tensile strength, Young's modulus and electrical conductivity of the PVA/GNR composite at a filling concentration of 3.6 vol.% approach 119.1 MPa, 5.3 GPa and 2.4 × 10-4 S m-1, with increases of 17%, 32.5% and 5.9 folds, respectively. The correlated mechanics is further rationalized by finite element analysis, the generalized shear-lag theory and the fracture mechanisms.