Stereospecific Group Transfer Polymerization of Methyl Methacrylate with Lewis-Acid Catalysis—Formation of Highly Syndiotactic Poly(methyl methacrylate)

Dinuclear Silylium-enolate Bifunctional Active Species: Remarkable Activity and Stereoselectivity toward Polymerization of Methacrylate and Renewable Methylene Butyrolactone Monomers

“…The activity of the MMA polymerization by the [ R SKA + HNTf 2 ] system is rather low, most likely due to the coordinating nature of the Tf 2 N À anion, thus typically requiring 24 h reaction time and giving a low catalyst TOF of only ∼80 h À1 . 13 23 are considerably more active than the typical GTP system using no such combinations, suggesting their possible involvement of the silylium-catalyzed process similar to what has been demonstrated for the R SKA + TTPB 9,10 and R SKA + [H(Et 2 O) 2 ]-[B(C 6 F 5 ) 4 ] systems. 17 This revelation points to a possibly broad implication of the silylium-catalyzed polymerization process in the rapid and living/controlled polymerization of other polar conjugated olefins.…”

Organocatalyzed Group Transfer Polymerization

“…Another important characteristic of this polymerization was the simultaneous control of the M n and stereoregularity, e.g., the polymerization of MMA in CH 2 Cl 2 at −55°C afforded a PMMA with an M n of 14.0 kg mol −1 , M w / M n of 1.04, and mm / mr / rr of 0/10/90 after 168 h polymerization. The high stereoregularity obtained from the Tf 2 NH‐promoted GTP was interesting because such a high stereoregularity was usually only observed for the GTP with the combined use of a transition‐metal catalyst and additive 35. It should be emphasized that the actual catalyst during the polymerization was the strong Lewis acid of Tf 2 NSiMe 3 generated from the reaction between Tf 2 NH and Me SKA, rather than Tf 2 NH, because Tf 2 NSiMe 3 was generated prior to the polymerization.…”

Silylium dual catalysis in living polymerization of methacrylates via In situ hydrosilylation of monomer

“…We employed strong BrØnsted acids paired with weakly coordinating perfluorophenylborate anions, [H(Et 2 O) 2 ][B(C 6 F 5 ) 4 ], [HN(Me 2 )Ph][B(C 6 F 5 ) 4 ], and a strong BrØnsted acid bearing a chiral disulfonimide counteranion, 2d to deliver the R 3 Si + catalyst that effects high‐speed living polymerization with a unique “self‐repair” features in the presence of water . Also worth noting here are the observations that the more advanced GTP systems using the R SKA initiator and additionally employing different combinations of a Lewis acid and a Me 3 Si‐containing reagent, such as [Me 3 SiOTf + B(C 6 F 5 ) 3 ], [Me 3 SiI + HgI 2 ], or [Me 3 SiI + RAl(OAr) 2 ], are considerably more active than the typical GTP system using no such combinations, which may indicate their possible involvement of the silylium‐catalyzed process similar to what has been demonstrated for the R SKA + [Ph 3 C][B(C 6 F 5 ) 4 ] and R SKA + [H(Et 2 O) 2 ][B(C 6 F 5 ) 4 ] systems …”

“…SKA initiator and additionally employing different combinations of a Lewis acid and a Me 3 Si-containing reagent, such as [Me 3 SiOTf 1 B(C 6 F 5 ) 3 ], 23 [Me 3 SiI 1 HgI 2 ], 24 or [Me 3 SiI 1 RAl(OAr) 2 ],25 are considerably more active than the typical GTP system using no such combinations, which may indicate their possible involvement of the silylium-catalyzed process similar to what has been demonstrated for the R SKA 1 [Ph 3 C][B(C 6 F 5 ) 4 ] 9,10 and…”