Simultaneous Chain‐Growth and Step‐Growth Polymerization of Methoxystyrenes by Rare‐Earth Catalysts

Abstract

The simultaneous chain-growth and step-growth polymerization of a monomer is of great interest and importance because it can produce unique macromolecules which are difficult to prepare by other means. However, such a transformation is usually difficult to achieve in one polymerization system because chain-growth polymerization and step-growth polymerization proceed by different reaction mechanisms. Reported here is the simultaneous chain-growth and step-growth polymerization of para- and meta-methoxystyrenes catalyzed by half-sandwich rare-earth alkyl complexes, and the step-growth polymerization proceeds by the C-H polyaddition of anisyl units to vinyl groups. This unprecedented transformation affords a new family of macromolecules containing unique alternating anisole-ethylene sequences. In contrast to para- and meta-methoxystyrenes, ortho-methoxystyrene exclusively undergo syndiospecific, living chain-growth polymerization by continuous C=C bond insertion to give perfect syndiotactic poly(ortho-methoxystyrene) with high molecular weight and narrow polydispersity (rrrr >99 %, M up to 280 kg mol , M /M <1.10).

Stereoselective Copolymerization of Unprotected Polar and Nonpolar Styrenes by an Yttrium Precursor: Control of Polar‐Group Distribution and Mechanism

“…Surprisingly, only the homopolymer P( o MOS) was afforded (see Table S2), thus suggesting that the coordination of polar monomers to the active metal center was too well favored to allow the coordination of nonpolar styrene, in agreement with a previous report about the copolymerization of ethylene with a vinyl ether . When meta ‐methoxystyrene ( m MOS) and para ‐methoxystyrene ( p MOS) were used, neither the homopolymerization of m MOS or p MOS nor copolymerization with St took place (see Table S2) . Thus, competitive coordination of the vinyl groups of p MOS, m MOS, and St with the polar methoxy groups to the active metal center failed.…”

Syndioselective Polymerization of Vinylnaphthalene

“…However, the commonly existing interaction between the Lewis basic polar group (such as ether) and the Lewis acidic metal center of the active species usually prohibited the polymerization of polar monomers. A fluorenyl carbene scandium catalyst reported previously by us was completely inert to MVN homopolymerization . In this work, the half sandwich precursor 1 also did not give a promising catalytic activity (run 13).…”

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

“…Recently, Hou and co‐workers reported a simultaneous chain‐growth and step‐growth polymerization of substituted styrene monomers at first time . Catalyzed by half‐sandwich rare‐earth alkyl complexes 10 (Scheme ), simultaneous chain‐growth and step‐growth polymerization were accomplished by using p MOS and m MOS to form novel macromolecules containing multiple branches of alternating anisole‐ethylene sequences.…”