Living Radical Polymerizations with Germanium, Tin, and Phosphorus Catalysts − Reversible Chain Transfer Catalyzed Polymerizations (RTCPs)

Abstract

A novel class of living radical polymerizations with germanium, tin, and phosphorus catalysts were developed. The polymerizations are based on a new reversible activation mechanism, Reversible chain Transfer (RT) catalysis. Low-polydispersity (M(w)/M(n) approximately 1.1-1.3) polystyrene, poly(methyl methacrylate), poly(glycidyl methacrylate), and poly(2-hydroxyethyl methacrylate) with predicted molecular weight were obtained with fairly high conversion in a fairly short time. The pseudo-first-order activation rate constant kact for the styrene/GeI4 (catalyst) system was large enough, even with a small amount of GeI4, explaining why the system provides low-polydispersity polymers from an early stage of polymerization. The retardation in the polymerization rate observed for the styrene/GeI4 system was kinetically proven to be mainly due to the cross-termination between the propagating radical with GeI3*. Attractive features of the germanium, tin, and phosphorus catalysts include their high reactivity hence small amounts (1-10 mM) being required under relatively mild conditions (at 60-100 degrees C), high solubility in organic media without ligands, insensitivity to air hence sample preparation being allowed in the air, and minor color and smell. The germanium and phosphorus catalysts may also be attractive for their low toxicity. The phosphorus catalysts may also be attractive for their low cost.

Macromolecular Architectures Designed by Living Radical Polymerization with Organic Catalysts

“…RTCP and RCMP can be facile and pervasive methodologies for various applications. We previously reported the use of RTCP and RCMP in preparing well-defined linear polymers including homopolymers, random copolymers, and diblock copolymers [16][17][18][19][20][21][22][23][24][25][26][27]. In this paper, we report new examples of diblock copolymers and summarize the diblock copolymers prepared in previous and current works.…”

“…We developed two mechanistically different systems referred to as reversible chain transfer catalyzed polymerization (RTCP) [16][17][18][19][20][21][22][23] and reversible coordination mediated polymerization (RCMP) [24][25][26][27].…”

Photo-Induced Living Radical Polymerization via Organic Catalysis

“…RCMP uses iodine as X (capping agent) and organic amines and organic salts as catalysts to drive the reversible activation (Scheme 1b). RCMP and our related LRP system [24][25][26] are the first LRP systems to use organic catalysts. An advantage of RCMP is that no special capping agents or metals are used.…”

Living Radical Polymerization via Organic Superbase Catalysis

“…We recently developed new LRP systems using iodine as a capping agent and organic molecules as catalysts. We developed two mechanistically different systems, referred to as reversible chain transfer-catalyzed polymerization (RTCP) [25][26][27][28][29][30][31] and reversible coordination-mediated polymerization (RCMP) [31][32][33][34][35]. These polymerizations are metal-free systems.…”