Development of Commercially Viable Thermomorphic Catalysts for Controlled Free Radical Polymerization

Controlled radical polymerization to build complex polymer architectures is of great commercial interest to DuPont. Using cobalt-mediated catalytic chain transfer technology (CCT) allows for precise control of molecular weight in the free-radical polymerization of methacrylate esters. The polymers produced via CCT are highly functionalized with vinyl end groups, making them ideal macromonomer precursors for a variety of specialty polymer architectures. However, the homogeneous cobalt catalysts currently used for CCT are intensely colored and difficult to remove from the product resin, thus limiting potential applications. Eliminating the metal and color contamination would significantly enhance the commercial feasibility of CCT technology. Heterogeneous catalyst supports for CCT have proved untenable due to the increased polydispersity of the product resins so homogenous polymer-tethered catalysts were therefore evaluated as an alternative to traditional solid supports. Several classes of thermomorphic cobalt catalysts were demonstrated to be efficient recoverable catalysts. Polyethylene-tethered cobalt phthalocyanine and porphyrin catalysts were chosen as leading candidates for commercial implementation due to their inherent stability and facile separation from the product resin.