Polysilane Dendrimers

Polysilanes, –(Si)_n–, are polymers that contain catenated silicon atoms, and their chemistry has attracted considerable interest during the last 30 years because of their electronic, optical, structural, and chemical properties [1]. In particular, the σ-conjugation of the –Si–Si– backbone has attracted much attention compared with analogous carbon polymer systems. Although, in contrast to the numerous reports on polysilanes with linear main chains, little attention has been devoted to their branched counterparts; hyperbranched polysilanes [2], ladder polysilanes [3], and organosilicon nanoclusters [4] have nevertheless been described. However, with the exception of ladder polysilanes, the precise structures of these branched polymers have not been sufficiently elucidated. This chapter deals with polysilane dendrimers from the initial [6] to the most recent report [20]. These dendrimers, which contain silicon atoms attached to three or four other silicon atoms, exhibit some interesting properties compared with their linear homologues [5]. As in other chapters of this book, the ‘1G(4,⁰3) end-group’ nomenclature system (see Fig. 4.1) is used. In this system, 1G denotes generation 1, the first number in parentheses denotes the branching functionality of the core (in this example a tetradendron dendrimer with first digit 4); the following superscript represents the number of spacer silicon atoms between the core and the next branching point; the following numbers represent functionalities of the silicon atoms in each subsequent generational layer; and finally the end-groups are specified by their chemical formulas