Molecular Dynamics Simulation of Polyamidoamine Dendrimer-Fullerene Conjugates:Generations Zero Through Four

Abstract

Previously the synthesis of the polyamidoamine (PAMAM) (G4)-C60 conjugate with a molar ratio of 1 : 30 was reported. Because PAMAM G4 has sixty-four primary amine groups, it was hypothesized that approximately two surface amine groups react with each fullerene molecule to form the conjugates. A computational energy minimization study of various G4 PAMAM-fullerene conjugates containing 1 dendrimer but different amounts of fullerenes shows excellent stability for the 1 : 30 dendrimer to fullerene product. Attempts to prepare other PAMAM dendrimer-fullerene (C60) conjugates, using generations G0-G3 of PAMAM and C60 via the same procedure in pyridine were not successful, possibly due to solubility differences. The same computational techniques used to study the G4 conjugates were then used to determine (1) the stability of the G0-G3 conjugates (with a 2 : 1 primary amine to fullerene ratio), and (2) their solubility in pyridine compared to the (G4)-C60 conjugate. The findings allow for a better understanding of structure-property relationships of these nano-hybrid materials, through investigation of the molecular shape and radius of gyration. The findings reported herein may lead to improved syntheses of fullerene-dendrimer conjugates of various sizes and a better understanding of their nanoscopic structures and topographical influences.