Synthesis of Inorganic Dendrimers

Summary Dendrimers are a special class of hyperbranched polymers, constituted of branched constitutional repeating units. Contrary to common polymers, dendrimers are not synthesized by polymerization reactions, but by the step-by-step approach around a central core unit. Most dendrimers are organic compounds with nitrogen or quaternary carbon or benzene ring as branching points, but several families of “inorganic” dendrimers have emerged, essentially based on either silicon or phosphorus as branching points. Despite the architectural similarity, organic and inorganic dendrimers differ in terms of methods of synthesis and characterization, and also by types of utilization. Inorganic dendrimers can offer completely new properties, as will be emphasized later in Chapter 10. The present chapter describes the synthesis of dendrimers comprising either silicon or phosphorus branching points with the emphasis on carbosilane and phosphorhydrazone dendrimers, both of which have obtained the largest attention of all inorganic dendrimers to date. Many other types of small dendrimers have been described in literature, but they will not be reported in this chapter, which focuses both on the above most widely used and also on the most original types of inorganic dendrimers. A few miscellaneous examples of dendrimers based on germanium, tin, or bismuth branching points will be given as well, although they are still rare among dendrimers.