Dendrimers hydroxyl surface

For metal ions that do not form either covalent bonds or strong complexes with the interior amine groups of PAMAM dendrimers, a new method for the synthesis of dendrimer-encapsulated metal nanoparticles has been reported [26]. For example, when G6 dendrimer (with surface hydroxyl group) -encapsulated copper is exposed to a solution containing ions more noble than copper,... 

Fig. 4.17 A copper cluster encapsulated within a PAMAM dendrimer with hydroxyl surface groups (PAMAM-OH) acting as a chemoselective catalyst for hydrogenation of carbonyl and olefin groups in water. The activity was dependent on the molar ratio of the Cu and PAMAM-OH used in the synthesis, which was ascribed to the size-specific chemical properties of the Cu clusters. The dendrimer-encapsulated Cu cluster was oxidized into Cu ions under aerobic conditions, but it could be regenerated by reduction with NaBH4 for use in catalytic applications. Reprinted with permission from ref. [103]. Copyright 2013 American Chemical Society...

The presence of a large number of chain-ends in the fully synthesized dendrimer molecules makes them highly soluble and also readily miscible, for example with other dendrimer solutions. The solubility is controlled by the nature of the end-groups, so that dendrimers with hydrophilic groups, such as hydroxyl or carboxylic acid, at the ends of the branches are soluble in polar solvents, whereas dendrimers with hydrophobic end-groups are soluble in non-polar solvents. The density of the end-groups at the surface of the dendrimer molecule means that they have proportionately more influence on the solubility than in linear polymers. Hence a dendritic polyester has been shown to be more soluble in tetrahydrofuran than an equivalent linear polyester. 

TRIDENDRON DENDRIMER AND GENERAL PROCEDURE FOR SURFACE MODIFICATION OF THE HYDROXYL TERMINATED DENDRIMERS... 

The dendrimer droplets were used as a tool to examine surface heterogeneity on the nanoscale [319]. Figure 32 shows two pairs of SFM images of the droplets deposited on mica (a,b) and a copolymer film (c,d), respectively. On mica, the hydroxyl terminated dendrimer showed the autophobic or pseudo-partial wetting behaviour as the droplets sit on a thin film of the same material [312,320]. 

Saville et al.1411 studied the U.—A (surface pressure-area) isotherms at the water-air interface at 25 °C for monomolecular films of the ethereal dendrimer series (i.e., the benzylic alcohol series represented by structures 50 in Scheme 5.12). They reported a strong dependence of the isotherms on molecular weight, which compared well with that observed for hydroxyl-terminated polystyrene. 

Standard synthetic methods are used to couple partially protected penta-erythritol to the core cell and subsequent dendrimer surfaces [82, 133]. Synthesis of the first generation involves displacement of bromide from C(CH2Br)4 with a masked pentaerythritol (bicyclic orthoester). One obtains three hydroxyl groups per terminal group after deprotection (Scheme 24). Therefore, a series that triples both its surface hydroxyl groups and its molar mass is obtained (see Table 5). 

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