Abstract: Devices and methods for actively controlling the production of multistage and multimodal polymers. The device may include a reaction vessel configured to contain a polymer solution and generate polymer reactions in at least two stages as well as one or more detectors configured to monitor at least one reaction characteristic of the polymer solution contained in the reaction vessel. The device may further include a controller coupled with the reaction vessel and the one or more detectors, the controller configured to actively control the development of a predetermined reaction characteristic by modifying at least one process control variable based on the at least one reaction characteristic monitored by the detector.