Aminolysis, polysilazanes

Reactions (l)-(5) illustrate known methods for forming silicon-nitrogen bonds of potential use in the formation of oligo- and polysilazanes. The most common method of forming silazanes is via ammo-nolysis or aminolysis as shown in reaction (1) (4,5) ... 

We have also explored the use of the dehydrocoupling reaction for the synthesis of preceramlc polysilazanes starting from the precursor MeNH-[H2SlNMe]x-H. As described above, MeNH-[H2SlNMe]X H Is produced by aminolysis of H2SiCl2 with MeNH2 under conditions where x 18-20 (Mn - 1150). 

Precursors that fall in this category are generically called polysilazanes or polysilsesquiazanes. Synthetic routes to these materials have been reviewed63,24 thus, we provide an overview of typical methods. The most common route to polysilazanes is via ammonolysis/aminolysis of chlorosilanes25-27. 

There are a number of published reviews on the synthesis of poly-silazanes. - " The present discussion is limited to a brief history and development of oligo- and polysilazane synthesis. The methods of synthesizing polysilazanes include (1) polymerization by aminolysis (or ammonolysis) of chlorosilanes, (2) ringopening polymerization of oligomeric cyclosilazanes, (3) deamination and condensation of bis- and tra-aminosilanes, (4) redistribution polymerization of chlorosilanes and aminosilanes, and (5) catalyzed dehydrocoupling of diamines and organosilanes. 

A number of processible nitrogen-containing ceramic precursors are also discussed. These include polyalazanes (Jensen, Chapter 32), cross-linkable vinyl substituted polysilazanes (Schwark, Chapter 5), mixed sol-gels fi om aminolysis reactions (Gonsalves, Chapter 16), and polyborazines (Sneddon and Paine, Chapter 27 and Kimura, Chapter 28) which serve as precursors to AIN, Si3N4, BN/AJN composites, and BN, respectively. Arylene and alkylene bridged polysilsesquioxanes (Loy, Chapter 11) and carborane-polysiloxanes (Keller, Chapter 31) have bIso been employed to make modified silicas. 

---