Polyethylene and polypropylene adsorption on Ti3C2Tx MXenes: a DFT study

Abstract

Polyolefins form a large class of polymers extensively used in industry. An approach to improve the properties of polyolefins to expand their applications is the incorporation of nanofillers. A new and promising family of nanofillers with potential to produce polyolefin-based nanocomposites with enhanced properties are MXenes, which comprise 2D transition-metal carbides and/or nitrides. In this work, a comprehensive series of Density Functional Theory (DFT) calculations was conducted to examine the interaction of the two most widely used polyolefins, polyethylene (PE) and polypropylene (PP), with Ti₃C₂T_x MXenes (T_x = O₂, F₂, S₂, Cl₂, and (OH)₂). The model systems consisted of single chains of either PE or PP adsorbed on the MXene surface in different configurations. The polymer-MXene binding energies, calculated as a function of MXene terminations, revealed that both polymers adhered more strongly to the O₂-terminated MXene, while adsorption on Ti₃C₂(OH)₂ was the weakest. In all cases, the relatively large polymer/MXene separation (ranging from 2.2 to almost 3 Å) implies that weak interactions (van der Waals with a hydrogen bonding component) predominate. It is also observed that PE/MXene binding energies were much higher than those of PP/MXene, thus indicating stronger interfacial adhesion is expected in PE/MXene composites. Consistent with the overall weak nature of the polymer/MXene interaction, electronic structure analysis shows that the metallic character of MXene was preserved regardless of surface termination or adsorbed polymer.