Siloxane dendrimer

Scheme 3 Siloxane dendrimer. Reprinted with permission from Majoral, J.-P. Caminade, A.-M. Chem. Rev. 1999, 99, 845-880. Copyright 1999 American Chemical Society.

Fig. 4.49 Synthesis of fourth-generation siloxane dendrimers (according to Muzfarov et al.)...

The first dendrimers of this type were reported by Rebrov and coworkers in 1989154. Reaction of MeSiC with (EtO MeSiONa followed by reaction with SOCI2 gave the SiCl-terminated first generation. Repetition of the (EtO MeSiONa and SOCI2 sequences led to formation of siloxane dendrimers up to the fourth generation (Scheme 14). 

Masamune and coworkers reported a divergent stepwise synthesis of siloxane dendrimers as shown in Scheme 15155. The third generation dendrimer was the largest obtained. Characterization techniques included 1H, 13C and 29Si NMR spectroscopy, mass spectroscopy and size-exclusion chromatography. 

Another stepwise approach to siloxane dendrimers was described by Morikawa and coworkers156 and is outlined in Scheme 16. Using the key building block, A, the researchers were able to construct dendrimers up to the third generation in 32% yield after purification. The dendrimers were characterized with NMR spectroscopy and intrinsic viscosity measurements, which indicated globular geometries. 

Muzafarov, A. M., Siloxane Dendrimers. In Polymer Data Handbook, 2nded. Mark, J. E., Ed. Oxford University Press New York, 2009 pp 1194-1195. 

Figure 12. Picture of the model 3rd generation siloxane dendrimer. The ellipsoids represent Gay-Berne particles and the spheres represent Lennard-Jones particles.

Atsushi Morikawa studied organic materials science at the Tokyo Institute of Technology. In 1992 he obtained his doctor s degree on siloxane dendrimers and polyimide-silica hybrid materials by sol-gel method. After a two-year spell as a research engineer at Asahi Chemical Company, he transferred to the Faculty of Engineering at Ibaraki University to continue his research on polyfether ketone) dendrimers and polyimides. 

Scheme 32.2 Synthesis of DHBA based siloxane dendrimer [8]...

From the Bond Angles and Lengths in Tables 32.2 and 32.3 it is clear that the DFT calculations do not significantly alter the overall structure of the Tin or siloxane dendrimers. This data supports our assumption that the DFT optimized structure of the Platinum dendrimer correlates with what would have been obtained if it had been possible to perform PM3 calculations. The subsequent PM6 calculations proved this assumption correct. 

The PM3 method gave the Delocalized Molecular Orbitals (DLMO) of the Tin and siloxane dendrimers. Those for the siloxane dendrimer have previously been reported [12] and will not be discussed here. The three Degenerate Highest... 

These compounds can be used for a variety of organosiloxane syntheses, where the process needs the alternate usage of different functional groups. For instance, siloxane dendrimers (4), linear sodiumoxysiloxanes (5), and others. 

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