Dendron rod-coil

In contrast to previously described structurally simple rod—coil molecules, these dendron rod—coil molecules (7) form well-defined ribbonlike 1-D nano-... 

Figure 12. (a) TEM image of nanoribbons formed in dichloromethane. (b) Schematic representation of supramolecular nanoribbon by self-assembly of dendron rod—coil molecules. (Reprinted with permission from ref 61. Copyright 2001 American Chemical Society). 

Dendronized polymers, a type of dendritic molecule, exhibit properties not only from the dendron they possess - high functionality and regularity - but also from the polymer segments that are connected to dendrons or used to coimect several dendrons. Many different architectures of dendronized polymers can be prepared, depending on the t5q)e of polymer used, where the dendrons are attached, and how many are introduced. These architectures include, among others, dendron-coil, dendron-rod, dendron-rod-coil, and dendron-coil-dendron. The dendron-mediated assembly of dendronized polymers has been reviewed by Rosen et al7 ... 

Perhaps some of the most exciting work using one-component dendritic gelators has been performed by Stupp and co-workers. They have investigated the assembly properties of so-called dendron rod-coil molecules (Fig. 18) [59]. These dendron rod-coils are effectively tri-block copolymers, which have a flexible (coil) polymer unit attached to a well-defined linear rigid rod unit, which is, in turn, grafted to a dendritic head unit. The synthesis of... 

Fig. 18 Dendron rod-coil molecule used for self-assembly of a one-dimensional nanoscale architecture, hence leading to the formation of gel-phase materials... 

Recently, Stupp and co-workers demonstrated that dendron rod-coil systems can have conjugated systems such as ohgothiophene incorporated into their rod segments [65]. These molecules formed gel-phase materials in organic solvents and self-assembly of the systems gave rise to a blue-shifted absorption spectrum, and a red-shifted, quenched fluorescence spectrum, hi... 

Recently, Tew et al. [73] reported the synthesis and characterization of triblock rod-coil molecules consisting of diblock coil segments of polystyrene and polyisoprene, and oligo(p-phenylenevinylene) (OPV) trimers as rod segments. On the basis of TEM and X-ray diffraction data, these molecules formed self-organized nanostructures, which in turn assemble into monolayers. The same group has also synthesized dendron rod-coil... 

Fig. 25 Chemical structure of the dendron rod-coil molecules and the formation of nanoribbons. (Reprinted with permission from Ref. [74]. Copyright 2004 American Chemical Society)...

As far as the criterion for sectioiung this review article is concerned, it is not straightforward. For conveiuence, we will review 1-D assemblies of molecular rods in terms of molecular architecture. We classify rod assemblers into six molecular categories (1) rod-coil molecifles, (2) macrocyclic molecules, (3) dendron-rod-coil molecules, (4) dumbbell-shaped molecules, (5) wedge-typed molecules, and (6) conjugate rods with lateral chains. We will describe biomimetic or bioconjugate amphiphiUc rods in the last section. 

In contrast to linear coil, the triblock molecule 23, consisting of bis(penta-ethylene glycol) dendrons as coil segments at both ends of the rod with same rod building block, self-organizes into 2D columnar and 3D bicon-... 

---