Application of (thio) urea/phosphazene base mixture, polyester and preparation method of polyester

The invention discloses application of a (thio) urea/phosphazene base mixture, polyester and a preparation method thereof, relates to the technical field of polyester synthesis, in particular to application of the (thio) urea/phosphazene base mixture, polyester and a preparation method thereof, and solves the problems of metal residues and low molecular weight of an existing polyester synthesis method. The (thio) urea/phosphazene alkali mixture is used for catalyzing polyester synthesis; the method comprises the following steps: adding (thio) urea, phosphazene base, cyclic anhydride and styrene oxide into a reaction container under anhydrous and anaerobic conditions, and reacting; and after the reaction is finished, diluting the obtained mixture with dichloromethane, slowly dripping into excessive ethanol to separate out a polymer, and then filtering and drying to obtain the polyester. According to the invention, the (thio) urea/phosphazene base catalyst is used for catalyzing ring-opening copolymerization of