Influence of Noncovalent Modification of Carbon Nanotubes by Polyethylene Glycol on Their Distribution in the Polymer Matrix

Abstract

In polymer nanocomposites filled with carbon nanotubes, it is very difficult to ensure uniform distribution of nanotubes in the polymer matrix, as well as the stability of this dispersion over time. Therefore, in such systems, over time, due to the strong van der Waals forces of attraction between individual nanotubes, aggregation of filler particles takes place. It leads to a transition from the nano to the micro level of their structural organization. This transition significantly affects the complex of functional properties of polymer nanocomposites filled with carbon nanotubes (CNTs). Therefore, the development of new approaches to the stabilization of nanoparticles in order to prevent their aggregation to create nanocomposite materials with improved functional characteristics is an actual task. The work is devoted to the study of the influence of non-covalent modification of carbon nanotubes on the degree of their distribution in the polymer matrix of polyethylene glycol. The peculiarities of CNT distribution of two types were studied: unmodified and non-covalently modified nanotubes. It was found that unmodified CNTs contained hydroxyl, carboxyl and lactone groups on the surface. The presence of these groups on the surface of CNTs allowed for their noncovalent modification. The analysis of microscopic images revealed that the modified CNTs are more evenly distributed in the polymer matrix than the unmodified nanotubes, which can be explained by the different nature of the interaction between the polymer matrix and the CNT. It is shown that for systems containing modified CNTs, a higher value of fractal dimension is observed, which indicates the formation of more fluffy aggregates with CNTs, while unmodified CNTs tend to form denser aggregates. Modification of CNTs with PEG is a promising method to increase the degree of distribution of nanotubes in the polymer matrix, which will significantly improve the properties of such nanocomposite materials.