Poly(4-vinylpyridine) adsorption on boron nitride nanotubes and hexagonal boron nitride: A comparative molecular dynamics study

One of the foremost challenges in the boron nitride nanotube (BNNT) community is selective separation of BNNTs from the as-produced mixture of various hexagonal BN (hBN) phases. Recently, a polymer with a pyridine group, poly(4-vinylpyridine) (P4VP) has proven to be effective for BNNT dispersion. Here, we performed all-atom molecular dynamics simulations to elucidate the selective dispersion mechanism by characterizing interfacial interactions of P4VP with 12 different types of BNNTs, as well as with 8 different sizes of hBN sheets. The results revealed a prominent effect of lattice curvature (i.e., tube diameter) and morphology (i.e., tubular or planar) on the polymer adsorption conformation and their binding energetics. Remarkably, P4VP tightly wrapped around BNNTs with a well-defined helical pitch, while it formed an extended random coil on planar hBNs. A comparative study on carbon nanotubes and graphenes also highlighted the critical role of electrostatic interaction of P4VP with partially charged BN lattice.