Single-Molecule Dendrimer-Hydrocarbon Interaction

We report our single-molecule fluorescence microscopy and molecular dynamics simulation studies on the interaction of poly(amidoamine) dendrimer and squalane hydrocarbon in aqueous solution. Our spectrophotometry measurements indicate that this interaction increases with the pH of the solvent. Our simulations show that squalane resides primarily on the perimeter of the dendrimer at low to neutral pH, but becomes encapsulated by the dendrimer at high pH. Using single-molecule fluorescence microscopy, we have identified that the binding between PAMAM and squalane is reversible. At a pH value of 8, the approaching, binding, and characteristic times of a single fluorescently-labeled dendrimer to squalane are 0.5 s, 7.5 s, and 0.5 s, respectively. Both our spectrophotometry measurements and simulations show that the interaction between PAMAM and squalane is stronger for lower generation dendrimers. This study facilitates our understanding of using dendritic and hyperbranched polymers for gas hydrate prevention in the petroleum indus-