Germanium‐ and Tin‐Catalyzed Living Radical Polymerizations of Styrene and Methacrylates

Abstract

Summary: Ge and Sn (non‐transition‐metal) catalyzed living radical polymerizations were developed. Low‐polydispersity (Mw/Mn ∼ 1.1–1.3) polystyrenes, poly(methyl methacrylate)s, poly(glycidyl methacrylate)s, and poly(2‐hydroxyethyl methacrylate) with predicted molecular weights were obtained with a 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, to explain 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 proved to be mainly due to the cross‐termination between the propagating radical with GeI. Attractive features of the Ge and Sn catalysts include their high reactivity hence small amounts (1–5 mM) being required under a mild condition (at 60–80 °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 Ge catalysts may also be attractive for their low toxicity.

Reversible Chain Transfer Catalyzed Polymerizations (RTCPs) of Styrene and Methyl Methacrylate with Phosphorus Catalysts

“…Notably, these concentrations are even lower than those (2-5 mM) needed for the previously studied highly effective Ge and Sn catalysts (GeI 4 , GeI 2 , SnI 4 , and SnI 2 ), although the temperature in the PI 3 system (100 8C) is higher than those in the Ge (80 8C) and Sn (60 8C) systems. [6,7] For the PI 3 system (Table 1), we used relatively large amounts (80-160 mM) of DCP (conventional radical initiator) due to its slow decomposition (the half lifetime is ca. 80 h).…”

“…We added a germanium (Ge) or tin (Sn) compound, e.g., GeI 4 , to the iodide-mediated polymerization. [6][7][8] GeI 4 works as a deactivator (XA) of Polymer , in situ producing GeI 3 (Scheme 1d). GeI 3 works as an activator (A ) of a polymeriodide (Polymer-I), producing Polymer and GeI 4 .…”

Schiff base as a novel kind of catalyst for reversible complexation‐mediated radical polymerization of methyl methacrylate

“…In short, this process uses a reversible chain transfer of Polymer‐I with a radical catalyst (A•) to generate Polymer• and deactivator [Scheme (a)]. The catalysts of RTCP include germanium (Ge), tin (Sn), phosphorus (P), oxygen (O), nitrogen (N), and carbon (C) centered radical that are formed in situ . RCMP resembles the mechanism of ATRP, which uses a halogen as X and combines with transition metal to induce the reversible activation process.…”

Simulation of reversible chain transfer catalyzed polymerization (RTCP): effect of different iodide based catalysts

“…In the presence of AI catalyst (GeI 3 -I, etc.) another reversible reaction mechanism called the reversible chain transfer (RT) coexists which results in a low polydispersity by activating Polymer-I frequently [1,[14][15][16][17][18][19][20]. RT equilibriums are sensitive to the catalyst activity and concentration, therefore various polymer architectures could be attained by employing different catalysts at several concentrations [19].…”