G2-dendrons

Based on IsraelachviUi s predictions, KeUermann et al. (2004) designed a cone-shaped dendro-calixarene molecule displaying two polar carboxylate-terminated G2 dendrons on one face and four C12 chains extending from the opposite face (Fig. 11.24). 

Figure 11.27 Schematic representation of the hexagonal columnar strucmre of an ABA trihlock copolymer with a G1 dendton and the body-centered cubic strucmre of an ABA triblock with a G2 dendron.

Cobalt complexes of dendritic phthalocyanines (Fig. 6.37) showed a 20% lower catalytic activity (TON 339 min-1 for G2 dendrons) as catalysts for the oxidation of 2-mercaptoethanol than non-dendritic phthalocyanines [56]. By way of compensation, however, the dendritic catalysts proved to be more stable than non-dendritic ones, which is probably attributable to enclosure of the metallo-phthalocyanine core unit by the dendrons. This also prevents molecular aggregation of the phthalocyanines in polar solvents and thin films. 

In contrast, recent kinetic investigation of the polymerization of spacerless G2 dendron-substi-tuted styrene and methylmethacrylate, respectively, in solution lead to the unexpected conclusion that above a certain critical monomer concentration a strong increase in the rate of the free radical polymerization is observed [21]. The results can be explained by self-organization of the growing polymer chain to a spherical or columnar superstructure in solution, depending on the degree of polymerization (DP, Fig. 2). The rate constants and low initiator efficiency lead one to conclude that the self-assembled... 

Scheme 10.2 Synthetic scheme of dendronized homologous polymer brushes from macromonomers carrying G2 dendrons.

The double-exponential growth typically involves the constmc-tion of fully protected dendrons of low generation, for example, a G2 dendron (Figure 10). The fully proteaed dendron is split into two fractions, where one part is deprotected in the core and the other fraction is deprotected at the peripheral chain ends. The two differently activated dendrons are finally... 

PBzE G1-G2 Dendrons carrying folate or Methotrexate Hydrazone Cancer No No No 352... 

Ishida et al. investigated the polycondensation of different monomers to aromatic polyamides with respect to the DB, namely 3,5-diaminobenzoic acid (AB2-monomer, DB = 32%), a G1 dendron (AB4-monomer, DB = 72%), and a G2 dendron (ABg-monomer, DB = 84%). The molecular weights of the resulting polymers were in the range of 100000- 200000 with a polydispersity of 3. ... 

Some features of the dendronized polymers obtained from the macromonomers of Table 1 will become important later in this article and are therefore emphasized in the following (1) Most of the macromonomers carry G1 or G2 dendrons. Exceptions are only (12) (G3), (16) (G3), (18) (G3 and G4), (23) (G4), (25) (G3), and (27) (G3 and G4) (2) Many dendrons are of the benzyl ether type whose terminal phenyl rings are either unsubstituted or have one to three long alkoxy or fluoroalkoxy chains. The corresponding polymers are important for a variety of reasons but are unreasonable candidates, of course, whenever chemical modification becomes an issue (3) This is where dendrons (7), (8), (10), (11), and potentially also (13) come into play which carry protected... 

Scheme 7 Structures of G1 and G2 dendrons with a tetracarboxylic acid hydrogen bonding motif, and a schematic of their self-assembly into hexameric supramolecular dendrimers and linear supramolecular polymers. ...

Figure 11 Schematic structures of a G2-dendron with a terminal alkyne focal core (G2-alkyne) and HBC 8, and Ulnstration of two-stage site-selective functionalization of tubularly assranbled 8 to form a radially diblock nanotube.

Figures 6a and b support our mechanistic and kinetic characterization of the domino dendron system. The kinetic analysis of G1 and G2 dendrons may serve as a rehable method to characterize other domino dendritic systems. It can also allow a better understanding and evaluation of the kinetic contributions of introducing different substituents on the core benzene ring, and of modifying the linker component of the triggering substrate.

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