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

pH Sensitive surfactants from lysine: assessment of their cytotoxicity and environmental behavior

The toxicity and environmental behavior of new pH-sensitive surfactants from lysine are presented. Three different chemical structures are studied: surfactants with one amino acid and one alkyl chain, surfactants with two amino acids on the polar head and one alkyl chain, and gemini surfactants. The pH sensitivity of these compounds can be tuned by modifying their chemical structures. Cytotoxicity has been evaluated using erythrocytes and fibroblast cells. The toxic effects against these cells depend on the hydrophobicity of the molecules as well as their cationic charge density. The effect of hydrophobicity and cationic charge density on toxicity is different for each type of cells. For erythrocytes, the toxicity increases as hydrophobicity and charge density increases. Nevertheless, for fibroblasts cationic charge density affects cytotoxicity in the opposite way: the higher charge density, the lower the toxicity. The effect of the pH on hemolysis has been evaluated in detail. The aquatic toxicity was established using Daphnia magna. All surfactants yielded EC50 values considerably higher than that reported for cationic surfactants based on quaternary ammonium groups. Finally, their biodegradability was evaluated using the CO2 headspace test (ISO 14593). These lysine derivatives showed high levels of biodegradation under aerobic conditions and can be classified as"readily biodegradable compounds"