Hydroxyl-terminated dendrimers

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

The ability to prepare well-defined intradendrimer metal nanoclusters depends strongly on the chemical composition of the dendrimer. Spectroscopic results, such as those shown in Fig. 7, indicate that when G4-NH2, rather than the hydroxyl-terminated dendrimers just described, is used as the template a maximum of 36 Cu + ions are sorbed most of these bind to the terminal primary amine groups. Reduction of a solution containing 0.6 mmol/1 CUSO4 and 0.05 mmol/1 G4-NH2 results in a clearly observable plasmon resonance band at 570 nm (Fig. 11) [122,124,125] which indicates that the Cu clusters prepared in this way are larger than 4 nm in diameter. This larger size is a consequence of ag-... 

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]. 

Figure 12.33 Divergent synthesis of a fourth generation hydroxyl-terminated dendrimer with triazine core via thiol-ene click chemistry. (From Killops et al., 2008. With permission from American Chemical Society.)...

Fr chet and TuUy have used poly(aryl ether) dendrimers, terminated with carbonate end groups as photoresists [99]. The aqueous insoluble carbonate terminated dendrimers were applied as a layer to a substrate. This dendritic layer was exposed subsequently to deep UV radiation or electron beam radiation and then baked to convert the masked areas of the dendritic carbonate coating to the deprotected and water-soluble polyphenoxide dendrimers by decarboxylation of the peripheral groups. The resultant deprotected polyphenoxide dendrimers exhibited differential solubility to the carbonate terminated dendrimers, which was exploited by removal of either the carbonate terminated or hydroxyl terminated dendrimer by washing with protic organic or aqueous solvents, respectively (Figure 8.15). 

In addition to hydroxyl-terminated PAMAM dendrimers, we also investigated the binding ability of amine-terminated G4-NH2. Figure 7 a shows the d-d... 

Fig. 19. Turn-over frequencies for hydrogenation of allyl alcohol and N-isopropyl acrylamide obtained in water using dendrimer-encapsulated Pd nanoparticles of constant average size. The hydroxyl-terminated PAMAM dendrimer generation varies from G4 to G8...

Zhao et al (70) developed a method for the synthesis of dendrimer-encapsulated metal nanoparticles based on sorbing metal ions into (modified) PAMAM dendrimers followed by a reduction. Dendrimers encapsulating copper, palladium, and platinum nanoparticles have been prepared. Hydroxyl-terminated PAMAM dendrimers were used to prepare encapsulated palladium (PAMAM generations 4, 6, and 8) and platinum (PAMAM generations 4 and 6) nanoparticles. The dendrimer-encapsulated palladium and platinum nanocomposites catalyzed the hydrogenation reaction of allyl alcohol and N-isopropyl acrylamide in water 71). 

Scheme 4.40. Synthesis of a complimentary series of hydroxyl, amine, and carboxylic acid terminated dendrimers. 

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. 

Another type of dendrimer, that has been used to encapsulate Au32 particles is hydroxyl-terminated fifth-generation dendrimers (G5-PAMAM). The particles were adsorbed on silica (0.3wt.% Au),108 and after washing and removal of the dendrimer under oxygen at 573 K, followed by reduction under hydrogen at 573 K, the supported gold particles were even larger than above (14.5 nm), probably because silica is not a support that easily leads to small particles. 

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