Dendrimer Assisted Dispersion of Carbon Nanotubes: A Molecular Dynamics Study

TL;DR

This molecular dynamics study investigates how PAMAM dendrimers can effectively disperse carbon nanotubes by reducing their binding affinity, with protonation enhancing dispersion efficiency, which could aid in separating CNTs by chirality.

Contribution

The paper demonstrates that protonated PAMAM dendrimers are more effective than non-protonated ones in dispersing CNTs, providing insights into their potential use for CNT separation.

Findings

Protonated dendrimers show fully repulsive interactions with CNTs.

Binding affinity decreases with higher dendrimer generations.

Chirality influences the PMF in protonated dendrimer wrapped CNTs.

Abstract

Various unique physical, chemical, mechanical and electronic properties of carbon nanotube (CNT) make it very useful materials for diverse potential application in many fields. Experimentally synthesized CNTs are generally found in bundle geometry with a mixture of different chirality and present a unique challenge to separate them. In this paper we have proposed the PAMAM dendrimer to be an ideal candidate for this separation. To estimate efficiency of the dendrimer in dispersion of CNTs from the bundle geometry, we have calculated potential of mean forces (PMF). Our PMF study of two dendrimer wrapped CNTs shows lesser binding affinity compared to the two bare CNTs. PMF study shows that the binding affinity decreases for non-protonated dendrimer and for the protonated case, the interaction is fully repulsive in nature. For both the non-protonated as well as protonated cases, the PMF increases with increasing dendrimer generations from 2 to 4 gradually compare to the bare PMF. We have performed PMF calculations with (6,5) and (6,6) chirality to study the chirality dependence of PMF. Calculated PMF for protonated dendrimer wrapped chiral CNTs is more compared to the protonated dendrimer wrapped armchair CNTs for all the generations studied. However, for non-protonated dendrimer wrapped CNTs such chirality dependence is not very prominent. Our study suggests that the dispersion efficiency of protonated dendrimer is more compared to the non-protonated dendrimer and can be used as an effective dispersing agent in dispersion of CNT from the bundle geometry.