Size-Selective, Noncovalent Dispersion of Carbon Nanotubes by PEGylated Lipids: A Coarse-Grained Molecular Dynamics Study

Phospholipids with tethered poly(ethylene glycol) chains (PLPEGs) offer efficient, noncovalent dispersion of carbon nanotubes (CNTs). Important questions concern the relation between micellar and CNT-assembled PLPEG structures, and the influence of PEG length on assembly and dispersion. We explore these questions here via coarse-grained molecular dynamics simulation. Employing two representative CNT diameters and a range of PEG molecular weights, we find (i) PLPEG aggregation number to vary inversely with PEG chain length, consistent with recent experiments, (ii) an assembled morphology to vary from micellar-like to monolayer-like, depending on PEG chain length and CNT diameter, (iii) micellar coatings to result in greater CNT dispersion ability, with a higher barrier for interparticle aggregation (84 kJ/mol) compared to monolayer coatings (60 kJ/mol), and (iv) good agreement between simulation and scaling theories of a brush-type PEG.