Dendrimer surfactants

The unique architecture of dendrimers enables the functionalisation of the large number of peripheral end groups with moieties in order to confer very different and desirable 

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The geometry and surface chemistry of the dendrimer assemblies can be varied through the addition of surfactants. These dendrimer/surfactant aggregates can be tuned to template the formation of the different phases of calcium carbonate [40]. In combination with hexadecyltrimethylammonium bromide (CTAB), small spherical aggregates were formed that induce the formation of vaterite. Over a period of five days, the vaterite was transformed into calcite. The use of the negatively charged surfactant, sodium dodecylsulfonate (SDS), result-... 

PAMAMs constructed starting with lipophilic C12 cores have been exploited as hosts for studies using the dye Nile red. Notably, aqueous fluorescence emission was significantly enhanced by the formation of a dendrimer-surfactant assembly upon amphiphile addition. Modification of PAMAM surfaces by treatment with epoxyalkanes,such as 1,2-epoxyhexane and 1,2-epoxyoctane. produced nanoscopic container molecules... 

N. J. Tomalia, D.A. Dendrimers with hydrophobic cores and the formation of supramolecular dendrimer-surfactant assemblies. Langmuir 1997, 13. 3136-3141. 

Dendrimers can be designed to have a hydrophobic interior and a hydrophilic periphery. This gives them properties that are similar to those of conventional surfactants, and they can solubilize hydrophobic substances such as pyridine in aqueous solution by including them as guest molecules. They are therefore effectively mimolecular micelles. 

Host-guest systems made from dendritic materials have potential in the areas of membrane transport and drug delivery [68, 84, 85]. In a recent report [136] Tomalia and coworkers investigated structural aspects of a series of PAM AM bolaamphiphiles (e.g., 50) with a hydrophobic diamino do decane core unit. Fluorescence emission of added dye (nile red) was significantly enhanced in an aqueous medium in the presence of 50 unlike the cases when 51 and 52 were added (Fig. 23). Addition of anion surfactants to this mixture generated supramolecular assemblies which enhanced their ability (ca.by 10-fold) to accommodate nile red (53). Further increase in emission was noted by decreasing the pH from the normal value of 11 for PAMAM dendrimers to 7. At lower pH values the... 

For some reviews, see (a) Majoral J-P (2007) Influence of cationic phosphorus dendrimers on the surfactant-induced synthesis of mesostructured nanoporous silica. New J Chem 31 1259-1263 (b) Puntoriero F, Nastasi F, Cavazzini M et al (2007) Coupling synthetic antenna and electron donor species a tetranuclear mixed-metal Os(II)-Ru(II) dendrimer containing six phenothiazine donor subunits at the periphery. Coord Chem Rev... 

One of the possible alternative to micelles are spherical dendrimers of diameter generally ranging between 5 and 10 nm. These are highly structured three-dimensional globular macromolecules composed of branched polymers covalently bonded to a central core [214]. Therefore, dendrimers are topologically similar to micelles, with the difference that the strnctnre of micelles is dynamic whereas that of dendrimers is static. Thus, unlike micelles, dendrimers are stable nnder a variety of experimental conditions. In addition, dendrimers have a defined nnmber of fnnctional end gronps that can be functionalized to prodnce psendostationary phases with different properties. Other psendostationary phases employed to address the limitations associated with the micellar phases mentioned above and to modnlate selectivity include water-soluble linear polymers, polymeric surfactants, and gemini snrfactant polymers. 

Arborol Dendrimers. The spherical topology of dendrimers resembles the size and shape of the Hartley model (1936) of a micellar aggregate formed by surfactant molecules (Fig. 11.2 Tomalia et al. 1990). Micellar stmctuies have a dynamic, spherical structure possessing a close-packed, solvent-incompatible core surrounded by an open, solvent-compatible layer. 

Saville PM, White JW, Hawker CJ, Wooley KL, Frechet JMJ. Dendrimer and polystyrene surfactant structure at the air-water interface. J Phys Chem 1993 97 293-294. 

The process utilizing supramolecular organization involves pore expansion in silicas. A schematic view of such micelles built from the pure surfactant and those involving in addition n-alkane is shown in Figure 4.9. Another example of pore creation provides a cross-linking polymerization of monomers within the surfactant bilayer [30]. As a result vesicle-templated hollow spheres are created. Dendrimers like that shown in Figure 4.10 exhibit some similarity to micellar structures and can host smaller molecules inside themselves [2c]. Divers functionalized dendrimers that are thought to present numerous prospective applications will be presented in Section 7.6. 

Kukowska-Latallo JF, Chen C, Eichman J, et al. Enhancement of dendrimer-mediated transfection using synthetic lung surfactant exosurf neonatal in vitro. Biochem Biophys Res Commun 1999 264(1) 253—261. 

As early as 1986 dumb-bell-shaped dendrimers were reported to form linear networks.[87,881 These surfactant-like dendrimers possessed external, branched, ball-shaped architecture connected to either sides of a linear alkyl chain interior (Figure 9.10) these dendrimers were termed arborols and were discussed earlier in detail (Section 4.12.1.1). 

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