Advances in Preparation Methods and Conductivity Properties of Graphene-based Polymer Composites

Publisher Copyright: © 2023, The Author(s).Graphene-based polymer composites with improved physical properties are of great interest due to their lightweight, conductivity, and durability. They have the potential to partially replace metals and ceramics in several applications which can reduce energy and cost. The obtained properties of graphene-based polymer composites are often linked to the way graphene is dispersed in the polymer matrix. Preparation techniques like solution mixing, melt blending, and in-situ polymerization have been used to obtain graphene-based polymer composites. Dispersing and aligning graphene fillers within the composite is a key factor in enhancing the thermal and electrical conductivity values of the composites due to graphene’s anisotropic properties. The effect of the preparation methods of these composites on their physical-chemical properties is discussed in this review where we presented the advances that were achieved so far in the preparation techniques used showing the highest values ever achieved for electrical andthermal conductivity for these graphene-based polymer composites. Also, we presented the possible applications where graphene-based composites can be utilized.Peer reviewe

Cellulose Functionalization Using N-Heterocyclic-Based Leaving Group Chemistry

There has been continuous interest in developing novel activators that facilitate the functionalization of cellulosic materials. In this paper, we developed a strategy in which trisubstituted triazinium salts act as cellulose preactivators. As leaving groups, these triazinium salts utilize N-heterocycles (pyridine, imidazole, and nicotinic acid). Initially, we optimized the synthetic route for developing these novel cellulose preactivators (triazinium salts), whose structures were confirmed using NMR spectroscopy. The surface zeta potential of cellulose changed from a negative value to a positive one after preactivation due to the cationic nature of these preactivators. To enhance the scope of the study, we functionalized the cellulose-preactivated materials with a series of amine- or hydroxy-containing aliphatic and aromatic hydrocarbons, nucleophilic amino acids (cysteine), colorants (2-aminoanthraquinone and 2-amino-3-methyl-anthraquinone), and biopolymer (zein protein). The treated samples were analyzed using FTIR, time-gated Raman spectroscopy, and reflection spectroscopy, and the success of the functionalization process was validated. To widen the scope of such chemistries, we synthesized four reactive agents containing N-heterocyclic-based leaving groups (pyridine and nicotinic acid) and successfully functionalized cellulose with them in one step. The proposed single- and two-step functionalization approaches will provide opportunities for chemically linking various chemical compounds to cellulose for different applications

Grafting of Wool with Alginate Biopolymer/Nano Ag as a Clean Antimicrobial and Antioxidant Agent : Characterization and Natural Dyeing Studies

There is a continuous search for green and sustainable materials and processes in textile dyeing and finishing. In the current study, wool yarns were grafted with Sodium Alginate-Silver nanoparticles (SA-Ag NPs) and consecutively dyed with Cochineal or Madder. The weight gain of the samples was measured to find the optimized SA-Ag NPs initial concentration, and Scanning Electron Microscopy (SEM) was used to study their surface morphology. The effects of the initial dye concentration, pH, temperature on the color strength of the dyed samples were investigated. It was found that the pretreatment enhanced the dye-ability, antimicrobial, and antioxidant characteristics of the samples noticeably. Under the same dyeing conditions, the fixation of dyes on the treated wool fibers was noticeably higher than that of the untreated wool fibers. The colorfastness characteristics of the treated samples dyed with Cochineal or Madder were slightly improved. The results clearly showed that the application of SA-Ag NPs on the wool samples could be considered as a green finishing process with promising antioxidant and antimicrobial activities. A very high level of antimicrobial efficiency (99%) was achieved after the pretreatment, which remained as high as 90% even after ten repeated washing cycles.Peer reviewe

Self-Healability of Poly(Ethylene-co-Methacrylic Acid): Effect of Ionic Content and Neutralization

Publisher Copyright: © 2022 by the authors.Self-healing polymers such as poly(ethylene-co-methacrylic acid) ionomers (PEMAA) can heal themselves immediately after a projectile puncture which in turn lowers environmental pollution from replacement. In this study, the thermal-mechanical properties and self-healing response of a library of 15 PEMAA copolymers were studied to understand the effects of the ionic content (Li, Na, Zn, Mg) and neutralization percentage (13 to 78%) on the results. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing were used to study the thermo-mechanical properties of PEMAA copolymers while the self-healing response was studied using the projectile test. Puncture sites were observed using scanning electron microscopy (SEM) and the healing efficiency was quantitatively measured using the water leakage test. Five different self-healing responses were observed and correlated to ionic content and neutralization. At high neutralization, divalent neutralizing ions (Zn and Mg) that have stronger ionic interactions exhibited brittle responses during projectile testing. PEMAA samples neutralized with Mg and Li at low concentrations had a higher healing efficiency than PEMAA samples neutralized with Zn and Na at low neutralization. The PEMAA copolymers with higher tensile stress and two distinct peaks in the graph of loss factor versus temperature that indicate the presence of sufficient ionic aggregate clusters had improved healing efficiency. By increasing the neutralization percentage from 20% to 70%, the tensile strength and modulus of the samples increased and their self-healability generally increased. Among the investigated samples, the copolymer with ~50% neutralization by Li salt showed the highest healing efficiency (100%). Overall, the strength and elastic response required for successful self-healing responses in PEMAA copolymers are shown to be governed by the choice of ion and the amount of neutralization.Peer reviewe