High molecular weight polysilazanes are synthesized by ring polysilazanes ring-opening polymerization. The main methods include anionic ring-opening polymerization and cationic ring-opening polymerization.

Ion-catalyzed ring-opening polymerization
Cyclodisilazane is a reactive monomer. Under the catalysis of sodium ions, anion ring-opening polymerization will occur to form high molecular weight polysilazane polymer, and the purity of the product can reach more than 98%. Polysilazane with high molecular weight was formed by ring opening polymerization of cyclodisilazane in hydrofluoric acid reaction solvent catalyzed by lithium ion.

Ring opening polymerization of cyclosilazane
Under the catalysis of octamethylcyclotetrasilazane potassium ion, the ring-opening polymerization reaction takes place at high temperature, and the polysilazane with certain molecular weight can be formed by adding end capping agent.
Cyclotrisilazanes in the presence of hexapenylcyclotrisilazanes lithium salt will occur ring-opening polymerization reaction, the increase of hexapenylcyclotrisilazanes content will increase the molecular weight of the polymer accordingly, and the characteristic coefficients of the polymerization products will be improved accordingly.
Synthesis of three novel polysilazanes 
Polysiloxane polymers generally have low molecular weight and poor thermal stability. The polysilazanes with a certain proportion of methyl groups show good ductility and thermal stability, which can effectively improve the heat resistance of polysilazanes.
The research of polysilazanes mainly focuses on the fields of ceramic precursors and ceramic fibers, but there are few reports on the research of improving the heat resistance of polysilazanes. The author designed the molecular structure of polysilazanes with good heat resistance through the ring-opening polymerization of octamethyclotetrazilazanes and the introduction of methyl groups, providing certain design ideas and theoretical basis for the molecular structure of polysilazanes with specific properties in the later stage. Specific research ideas are as follows: The ring-opening polymerization was carried out using octamethyclotetrazilazane as ring-opening monomer, hexamethyclodisilazane as end capping agent and toluene as reaction solvent. The ring-opening polymerization was carried out using ruthenium-based catalyst as initiator under the protection of dry nitrogen.