Silyl Ether Containing Dendrimers with Cyclic Siloxane Cores

About three decades ago a remarkable cascade-type molecule was reported by Vögtle and his co-workers [1, 2]. This development set the stage for new types of polymers with a high degree of isomolecularity that are now widely known as dendrimers (see Chapter 1). In the years that followed, a number of different compositions of dendrimers, including amidoamine-, ether-, amine-, and ester-type dendrimers, etc. as well as their hetero-atom homologues has been prepared by many organic and inorganic chemists [3–6]. Among these, the introduction of silicone and organosilicon moieties into dendrimer structures has resulted in very unique silicon-containing dendrimers with considerable structural versatility [7–9]

One of the most versatile groups of organosilicon dendrimers is the carbosilanes (see Chapter 3), which often have four allylic branches emanating from a single central silicon atom (core) (0G(4-n); where n = 1–2). Physical properties of such dendrimers are gradually altered with increasing number of silicon-based moieties, branch units, and by addition of other functional groups to the silicon atoms in the peripheral region. The siloxane dendrimers with Si–O bonds in their main skeleton were reported earlier than the carbosilane dendrimers with Si–C bonds by Muzafarov et al. (see Chapter 2). The synthesis of these dendrimers, where silicon atoms form branch junctures with three Si–O bonds, was performed starting from trichloromethylsilane as a core, 0G(3)-Cl, using repetitive substitution of the chlorosilyl bond with ethoxy groups and their subsequent conversion back to chlorosilanes by thionylchloride (see Chapter 2)