清洁能源化学与材料实验室知识库

A new series of N-methylfulleropyrrolidines bearing oligo(poly(ethylene oxide))-appended Percec monodendrons (fulleromonodendrons, 4a–f) have been synthesized. The substituted position of the oligo(poly(ethylene oxide)) chain(s) on the phenyl group of the Percec monodendron for 4a–f was varied, which is at the 4-, 2,4-, 3,5-, 3,4,5-, 2,3,4- and 2,4,6- position, respectively. 4a–e are obtained as solids at 25 °C and can self-organize into lamellar phases as revealed by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements, while 4f appears as a viscous liquid. The substitution patterns of the oligo(poly(ethylene oxide)) chain(s) also significantly influence the solubility of 4a–f, especially in ethanol and water. Formation of self-organized supramolecular structures of 4d and 4e in water as well as 4d in ethanol is evidenced from UV–vis and dynamic light scattering (DLS) measurements. Further studies in water using various imaging techniques including transmission electron microscopy (TEM), freeze-fracture TEM (FF-TEM), cryo-TEM and atomic force microscopy (AFM) observations revealed the formation of well-defined vesicles for 4d and plate-like aggregates for 4e, indicating that the aggregation behavior of the fulleromonodendrons is highly dependent on their molecular structures. For 4d in ethanol, only irregular aggregates were noticed, indicating the solvent also plays a role on regulating the aggregation behavior. After functionalization with the Percec monodendrons, 4a–f can preserve the intriguing electrochemical properties of pristine C₆₀ as revealed by cyclic voltammetries. The thermotropic properties of 4a–f have also been investigated. It was found that all of them show good thermal stability, but no mesophases were detected within the investigated temperature ranges.