Dendrimers carbosilane-poly

Spin-coating films of other compositionally different dendritic macromolecules such as carbosilane dendrimers and hyperbranched poly(styrene) were studied by Sheiko et al. [20-22] using tapping mode AFM. 

The exterior of carbosilane dendrimers can also serve as initiator sites for polymerization, in which case the dendrimers serve as cores for star polymers. Vasilenko and coworkers95 synthesized a multilithiated carbosilane dendrimer which they then used as an initiator for the ring-opening polymerization of hexamethylcyclotrisiloxane to yield star polymers of narrow weight distribution (Scheme 7). The researchers later extended this work to polymerize styrene, isoprene and ethylene oxide96,97. Star poly(ethylene oxides) were also prepared using hydroxy-terminated carbosilane dendrimers as the core98,99. 

Star poly(methylmethacrylates) were synthesized via atom transfer polymerization using a small carbosilane dendrimer functionalized with a tertiary bromide moiety as an initiator core (Figure 12)100,101. a convergent approach to star polymers with a carbosilane dendrimer core was described in a report by Allgaier and coworkers102, in which living poly(butadienyl-lithium) arms were coupled with various SiCl-terminated carbosilane den-drimers. Utilizing smaller dendrimers with lower functionality was found to yield nearly ideal results in terms of substitution and polydispersity. 

In contrast to the PAMAM-bound catalysts, chiral dendrimers based on rigid poly(phenylethyne) and flexible carbosilane backbones without heteroatoms proved to be highly efficient catalysts in such alkylation reactions. Excellent enantioselectivities in the asymmetric addition of dialkylzincs to aldehydes (up to 93% ee) and N-diphenylphosphinyli mines (up to 94% ee) were achieved. 

Carbosilane dendrimer 2,921" [GO] 1.4" [GO] CH2CI2 Ring-opening metathesis poly- [159,160]... 

The efficiency of the linking reactions of polychlorosi-lanes with poly(dienyl)lithium compounds has been documented by synthesis of well-defined, narrow molecular weight distribution, 18-armed star-branched polyisoprenes, polybutadienes, and butadiene end-capped polystyrenes by linking reactions with a decaoctachlorosilane [(SiCl)ig] [256, 257]. The linking reactions of poly(butadienyl)lithium (Mjj = 5.3-89.6 x 10 g/mol) with carbosilane dendrimers with up to 128 Si-Cl bonds have been reported to proceed... 

The first dendrimers made were based on PAMAM (Tomalia et al. 1985). It was also the first to be scaled up and commercialized under the name of starburst dendrimers. Poly(propylene imine) (PPI) and poly(ethylene imine) (PEI) are some of the other commonly used dendrimers for drug and gene delivery. Since then, many new dendrimers have been synthesized that possess various properties for specific applications. Incorporation of inorganic molecules into dendrimer structures has shown distinct advantages. For example, the recent carbosilane dendrimers with surface lactose entities seem to possess inherent antiviral properties (Oka et al. 2009). In another case, fluorine molecules were incorporated into the core of dendrimers (Jiang and Yu 2010) that offer potential in fields such as catalysis. Polyester (Padilla De Jesus et al. 2002), polypeptide (Choe et al. 2002), triazine (Lim and Simanek 2008), and poly glycerol (Calderon et al. 2009) are organic dendrimers that have been attached to chemothera-peutics to increase the efficacy of treatment. Many other useful chemical compositions such as the poly (ester acrylate/amide) (PEA) (Swanson et al. 2007) and poly(ether hydroxylamine) (PEHAM) (Tomalia et al. 2006) are commercially available and used in biomedical applications. 

Linking with multifunctional silyl chlorides has been extended to stars with arm functionalities over one hundred by utilizing the linking reactions of poly(butadienyl)lithium with carbosilane dendrimers containing up to 128 Si-Cl bonds [21]. Star-branched polybutadienes with more than 250 arms were reported for the linking reactions of poly(butadienyl)lithium with the product from hydrosilation of 1,2-polybutadiene [22]. 

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