Polysilazane materials are mainly used in the fields of ceramic precursor preparation, coating material synthesis and medical surgery. The ceramic materials made by cleavage and polymerization of polysilazane have the advantages of good fluidity, designable components, good heat resistance and uniform product composition, etc. At the same time, the process of cleavage and polymerization of polysilazane is simple and the reaction temperature is low, so it is widely used in the preparation of foam ceramic materials.
With the continuous development of modern science and technology, the research on the design of polysilazane molecular structure, product synthesis and application has made an exceptionally rapid development, and the research results related to the construction of polysilazane with a clear molecular structure have been reported. In recent years, domestic and foreign research on polysilazane ceramic spinning ability, material coating applications and other research is more extensive, about polysilazane heat-resistant performance research needs to be further in-depth. The author reviewed the existing polysilazane synthesis methods and reaction principles, using the polysilazane molecular structure can be designed to special chemical properties, put forward the synthesis of heat-resistant high molecular weight polysilazane research ideas, outlook for the development of polysilazane prospects and research direction.
I. Synthesis of low molecular weight polysilazanes
1.1 Aminolysis and ammonolysis reaction
The main synthesis method of low molecular weight polysilazane is aminolysis, ammonolysis polycondensation reaction, and the main steps are as follows: ammonia is passed into the chlorosilane benzene solution configured with dimethyldichlorosilane (Me2SiCl2), methylhydroxydichlorosilane (MeSiHCl2) and toluene, and the reaction is continued with mechanical stirring, precipitation, drying and filtration, and the benzene solvent is washed and fractionated. It was shown that the higher the proportion of Me2SiCl2 content in the chlorosilane benzene solution, the less time was required for the ammonolysis reaction and the higher the molecular weight of the reaction product. The low molecular weight polysilazane prepared by this method has an average molecular weight of 1300, but is chemically more unstable, the body can be crosslinked rapidly, and the reaction product can be prepared by high temperature cracking to produce high yield silicon nitride ceramics mixed with pure silicon.
1.2 Synthesis of cyclosilazane
Studies have shown that cyclotri- and cyclotetra-silazanes can be synthesized through the ammonia decomposition of halosilanes containing bifunctional groups, and poly-silazanes can be synthesized through the reaction of ammonia, aminodilithium, and dichlorosilane as a tetradecamer of silicon nitride. Tong Xiujun et al. used Me2SiCl2 as the reaction monomer, reacted with solid ammonium chloride and ammonia, and recrystallized to obtain octamethylcyclotetrasilazane.
Synthesis of high molecular weight polysilazanes
High molecular weight polysilazanes are mainly synthesized by ring-opening polymerization of cyclic polysilazanes, and the main methods are anionic ring-opening polymerization and cationic ring-opening polymerization.
2.1 Ion catalyzed ring opening polymerization
Cyclodisilazane is the reactive monomer, anionic ring-opening polymerization will occur under the effect of nano-ion catalytic, generating high molecular weight polysilazane polymers, and the purity of the product can reach more than 98%. Cyclodisilazane in hydrofluoric acid reaction solvent, lithium ion catalyzed ring-opening polymerization reaction occurs, resulting in high molecular weight polysilazane polymer.
2.2 Ring-opening polymerization of cyclodisilazane
Octamethylcyclotetrasilazane under the catalytic effect of potassium ions, high temperature reaction, ring-opening polymerization reaction occurs, the addition of capping agent can form a certain molecular weight of polysilazane.
Cyclotrisilazane under the action of lithium salt of hexaphenylcyclotrisilazane will occur ring-opening polymerization reaction, the increase in the content of hexaphenylcyclotrisilazane will correspondingly increase the molecular weight of the polymer, the polymerization product of the characteristic coefficients will be improved accordingly.

Room termperature curing polysilazane, pls check IOTA 9150, IOTA 9150A. 
High termperature curing polysilazane, pls check IOTA 9108, IOTA 9118.