Ternary poly(2-ethyl-2-oxazoline)-polyvinylpyrrolidone-graphene nanocomposites: Thermal, electrical, dielectric, mechanical, and antibacterial profiling

Abstract

Graphene-based poly(2-ethyl-2-oxazoline) (PEOX) and polyvinylpyrrolidone (PVP) blend-matrix nanocomposites were prepared employing different weight percentages of graphene nanoplatelets as filler by ultrasonication assisted solution casting method. These nanocomposites were explored for their thermal, electrical, dielectric, and mechanical properties, and antimicrobial efficiency. Thermogravimetric analysis demonstrated that graphene operates as a barrier to limit thermal diffusion across the PEOX-PVP blend matrix, and hence, improve thermal stability of nanocomposites. The dielectric and electric properties such as dielectric constant, dielectric loss, loss tangent and electrical conductivity of PEOX-PVP-10 wt% graphene nanocomposite were found to increase with temperature. The presence of semi-circles in the Cole-Cole plot indicated the existence of a relaxation process in the conduction mechanism of the nanocomposite. AC electrical conductivity, σAC, of PEOX-PVP-10 wt% graphene nanocomposite was found to obey Jonscher's power law. The temperature-dependent behavior of frequency exponent, s, of σAC discusses the applicability of correlated barrier hopping (CBH) model. The extracted DC conductivity from AC conductivity studies was found to be temperature-dependent and obey Arrhenius relation with activation energy of conduction, Ea, of 0.41 eV and 0.39 eV in the lower and higher temperature regions, respectively. The mechanical properties of nanocomposites were enhanced dramatically when graphene loading was increased, demonstrating that a better interaction exists between graphene and the PEOX-PVP blend matrix. PEOX-PVP-15 wt% graphene nanocomposite showed superior mechanical properties (tensile strength: 9.18 MPa and Young's modulus: 3.19 MPa) among the synthesized nanocomposites. Further, the antibacterial activities of these nanocomposites against Gram-negative (E. coli) and Gram-positive (E. facecalis) bacteria revealed differential action.