Ordered Dendritic Nanorods with a Poly(p-phenylene) Backbone

Abstract

The degree of polymerization (DP n ) of poly(p-phenylene) (PPP) 3 with appendant third-generation, Fréchet-type dendrons was determined as 110 after a chemical modification. This DP n is extraordinarily high and shows that the mechanistically complex Suzuki polycondensation can thus be employed even in the case of sterically highly loaded (dendronized) AA-type monomers, which paves the way to obtain extremely rigid nanorods. A molecular model of 3 was obtained by molecular dynamics simulations which show that the diameter of the rodlike dendrimer fluctuates between approximately 2 and 4 nm in vacuo. Scanning force microscopy (SFM) on 3 adsorbed on graphite indicates the formation of multilayer films made of densely packed nanorods. SFM with molecular resolution reveals highly ordered domains in which the molecules are packed parallel to each other, separated by a lateral periodicity of 4.8 ± 0.5 nm. Lateral and vertical spacings indicate that the (110) plane of the densely packed nanorods is exposed at the film surface. SFM further indicates that different domains exhibit three molecular orientations, reflecting the 3-fold symmetry of the graphite substrate. Chain ends can be resolved at grain boundaries. Time-dependent SFM experiments show reorientation of small domains on a time scale of minutes.

Dendronized Polymers: Synthesis, Characterization, Assembly at Interfaces, and Manipulation

“…For the case of a similar polymeric dendrimer, P16/17(G3), this is demonstrated in Figure 12. [51] These results show that the ultrathin layers of the described dendronized polymers offer the possibility to orient the polymeric backbones along the substrate axes, and to access molecular dimensions in arrays by SFM imaging. To determine the properties of single molecules, such as persistence lengths or Youngs or bending moduli, it is desirable to prepare submonolayers with isolated single molecules on the surface.…”

“…The MD simulations were performed in vacuo with polymers P12(G3) [50] and P16/17(G3), [51] which carry the same G3 dendrons but differ by the average distance between the dendrons anchor groups (P12(G3): 2.50 , P16/17(G3): 8.25 ) and the flexibility of the backbone ( Figure 5). Unfortunately solvent molecules could not considered due to the enormous number of atoms already present in the polymers.…”

“…Phase-contrast SFM images (tapping-mode) of an ultrathin film of P16/17(G3) on HOPG. [51] The rows are attributed to molecules which are predominantly oriented parallel to the surface as well as to each other. Their orientation within the surface plane also reflects the threefold symmetry of the substrate (three molecular orientations denoted A, B, and C in a)).…”

Isolierte molekulare Drähte

“…[147] Am häufigsten werden die PolybenzyletherDendrone verwendet, die von Hawker und FrØchet entwickelt wurden (Abbildung 18). [148] Wie [147g, [149][150][151] Aus diesem Grund handelt es sich bei den meisten Angaben von n n um Schätzungen, doch schon diese Werte sind nützlich für die Interpretation der Eigenschaften dieser Materialien.…”

Hydroxy-Functionalized Dendritic Building Blocks

“…Some of these macromolecules may be ceeded very cleanly and gave the corresponding carboxylic considered as molecular objects with a cylindrical acid 2b in 90% yield. shape [2] [3] . In order to be able to engineer the properties of this intriguing class of macromolecules [4] it would be imScheme 1.…”