Phosphorus and nitrogen containing polysiloxane as well as preparation method and application thereof

The invention discloses phosphorus and nitrogen containing polysiloxane and a preparation method thereof, and the preparation method comprises the following steps: (1) mixing amino polysiloxane with an anhydride monomer, and reacting at 80-140 DEG C for 1-8 hours to obtain carboxyl functionalized polysiloxane; and (2) reacting the carboxyl functionalized polysiloxane prepared in the step (1) with a phosphorus-containing monomer at 60-150 DEG C for 4-16 hours to obtain the phosphorus and nitrogen containing polysiloxane. The phosphorus-nitrogen-containing polysiloxane takes a silicon-oxygen bond as a main chain structure and imino groups, carboxyl groups and phosphorus-containing groups as side group structures, a siloxane chain is relatively soft and can provide good toughness for epoxy resin, the imino groups and the phosphorus-containing groups can improve the flame retardant property of the epoxy resin, and the carboxyl groups can participate in a resin curing reaction, so that the flame retardant property