2009 | OriginalPaper | Buchkapitel
Polyhedral Oligomeric Silsesquioxane Dendrimers
verfasst von : Katherine J. Haxton, Russell E. Morris
Erschienen in: Silicon-Containing Dendritic Polymers
Verlag: Springer Netherlands
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Dendrimers have been prepared with a wide variety of core molecules since the first patents and publications in the early 1980s (see Chapter 1) [1–3]. The most common core molecules (e.g. ammonia, ethylenediamine, pentaerythritol) permit 2–4 branches although some molecules may give greater branch multiplicity. Polyhedral oligo-meric silsesquioxanes (POSS) allow eight branches to radiate from a silicon-oxygen core. Dendrimers based on POSS were first reported in 1993 and have resulted in many publications to date [4].
Siloxanes are molecules with the general formula [RSiO
x/2
] where R is an organic group or silicon species. Siloxanes may be discrete molecules, two-dimensional ladders or networks, or three-dimensional cages or polymers. The siloxane linkage, Si–O–Si is formed when different units join to form larger molecules. Siloxy groups [R
3
SiO
1/2
] are good terminal groups because they halt formation of larger siloxane networks, siloxane [R
2
SiO
2/2
] groups are ideal candidates for forming long chain-like molecules, while silsesquioxanes [RSiO
3/2
] and silicates [SiO
4/2
] are most commonly found in three-dimensional structures, both random polymers and oligomers, due to the number of siloxane linkages that can be created. In all cases, a large number of structures with a large number of functionalities have been reported [5]