Isotactic-b-Syndiotactic Stereoblock Poly(methyl methacrylate) by Chiral Metallocene/Lewis Acid Hybrid Catalysts

Abstract

Stereoblock polymerization with chiral ansa-metallocene/strong Lewis acid hybrid catalysts capable of switching stereospecificity of the methyl methacrylate polymerization produces the highly stereoregular isotactic-b-syndiotactic stereoblock poly(methyl methacrylate).

Low-temperature polymerization of methyl methacrylate emulsion gels through surfactant catalysis

“…The glass transition temperatures (T g ) of extracted PMMA, determined from the mid-point of the glass transition in the heat flow curves (vide infra), were observed between 98 and 100°C from both polymerized emulsion and emulsion gel samples. These T g 's are in consistent with the observations for the PMMA with similar tacticities [17,33]. The glass transition was primarily a reversing transition: the intensity of the reversing heat flow was much larger than that of the non-reversing heat flow.…”

Stereospecific polymerization of methacrylates by metallocene and related catalysts

“…The switching of growing polymer chain from the isospecific, cationic Zr site to the syndioselective, anionic Al site was demonstrated by the successful synthesis of highly stereoregular isotactic‐ b ‐syndiotactic stereodiblock PMMA (Scheme ) 18. In this sequential polymerization, the first portion of MMA was polymerized with rac ‐(EBI)ZrMe + MeB(C 6 F 5 ) to an isotactic block via the living isospecific, cationic zirconocene enolate propagating species E .…”

Stereospecific Olefin Polymerization Catalyzed by Metallocene Complexes

“…Chen et al showed that stereoregularity greatly depends on co-catalysts: 44 and 46 with borane give isotactic poly(MMA) by catalytic-site control, while these catalysts with the alane Al(C 6 F 5 ) 3 give syndio-rich poly(MMA) by chainend control [144]. They achieved iso-b-syndio stereoblock poly(MMA) using the borane and the alane in one pot [145].…”