Method for preparing linear macromolecules with controllable molecular weight by solution polycondensation reaction

The invention relates to a method for preparing linear macromolecules with controllable molecular weight by a solution polycondensation reaction. The method comprises five steps, i.e., preparing a reaction solution, controlling the reaction, computing product molecular weight, establishing a mathematical relation between reaction terminating current and the product molecular weight, and controlling the product molecular weight. Compared with the prior art, the method disclosed by the invention has the advantages that the viscosity of a solution polymerization system can be determined through the size of electric stirring device output current, and then, the molecular weight of a polymer is effectively controlled in a preparation process. The method has universality to solution polymerization reactions and is applicable to the preparation of various kinds of polymers such as polybenzimidazole, polyketone, polysulfone, polyether and polyamide. According to the method, the control on the molecular weight of the linear macromolecules to be prepared is accurate, and meanwhile, only a current measuring and displaying device (e.g., an ammeter) in series connection with an electric stirring device is additionally arranged outside a reaction device, so that the reaction device is simple, and the operation is easy. The method is of great significance for the preparation of the linear macromolecules with controllable molecular weight.