Polycarbosilazane polymers

The earliest report of fibers containing silicon and nitrogen is by Verbeek (11). Chlorosilanes and amines are used to prepare polycarbosilazane polymers, which are converted into amorphous SiCN-containing ceramic fibers (equation 7). 

There are several structurally different types or polymers that are suitable precursors for ternary Si-C-N ceramics. By far the most investigated precursors are polysilazanes of the general type [Si(R )(R°)N(R°)] (R, R°, R° = H, alkyl, aryl, alkenyl, etc.). In contrast to the limited number of starting compounds, H SiCl(4 ) (x = 0-3) as the silicon source and NH3 or H2N-NH2 as the nitrogen source for synthesis of polysilazanes as precursors for binary Si-N ceramics, the chemistry of polycarbosilazanes, that is, carbon-containing or modified polysilazanes, is very multifaceted. The attachment of various organic groups to the silicon atoms allows adjustment of their physicochemical properties, to control their thermolysis chemistry, and also to influence materials properties. The first... 

Pd2(dba)3 is an excellent catalyst to give a high molecular weight polymer (M = 16,300) at room temperature in a short time (2h). We extended the reaction to the polymerization of p-BSB with other labile-hydrogen-containing compounds, such as ammonia, disilanol, aliphatic and aromatic diols, and dicarboxylic acids to prepare a series of silphenylene-containing polymers, including polycarbosilazane, polycarbosiloxanes, poly(silyl ether)s, and poly(silyl ester)s. 

In recent years silicon-based polymers were investigated as precursors for SiC and Si3N4 ceramics, as well as for crystalline or amorphous Si/C/N and SiC/Si3N4 composite materials [1, 2]. This is due to the very interesting chemical and thermomechanical properties of silicon carbonitrides, such as high hardness, toughness and corrosion resistance. In most of these studies polycarbosilanes, polysilazanes and polycarbosilazanes were applied [3]. 

Delverdier, M. Monthioux, D. Mocaer and R. Pailler, Thermal behavior of polymer-derived ceramics. IV Si-C-N-0 fibers from oxygen-cured polycarbosilazane, J. Europ. Ceram. Soc., 14,313-325 (1994). 

High Polymers, Chem. Rev. 89,1359,1989 M. Birot, J.-P. Pillot, J. Dunogues -Comprehensive Chemistry of Polycarbosilanes, Polysilazanes and Polycarbosilazanes as Precursors of Ceramics. Chem Rev. 95, 1443,1995. 

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