Binuclear Scandium Initiators for the Syndiospecific Triblock Copolymerization of Styrene with ε-Caprolactone

Bis(phosphinophenyl)amido-Ligated Binuclear Rare-Earth Metal Complexes for Highly cis-1,4-Selective Polymerization of 1,3-Conjugated Dienes

A series of binuclear rare-earth metal complexes based on the ligands containing bis(phosphinophenyl)amido-PNP unit are successfully synthesized. All the ligands and the corresponding binuclear complexes are fully characterized by NMR spectra (1H, 13C, and 31P). In conjunction with [Ph3C][B(C6F5)4], all the binuclear complexes exhibited high catalytic activity and high cis-1,4-selectivity (>99%) toward the polymerization of 1,3-conjugated dienes (isoprene, β-myrcene and β-farnesene) with excellent livingness at room temperature or even 80 °C.

Controlled, one-pot synthesis of recyclable poly(1,3-diene)-polyester block copolymers, catalyzed by yttrium β-diketiminate complexes

The one-pot synthesis of well-defined block copolymers of olefins/1,3-dienes and polar monomers, such as cyclic esters and acrylates has long been the focus of intense research. Cationic alkyl rare earth metal catalysts, activated by organoborates, have shown to be promising for the polymerization of isoprene or styrene and ε-caprolactone. In this study, we synthesize a series of yttrium bis(alkyl) complexes supported by simple β-diketiminate ancillary ligands. Subtle changes have been made to the β-diketiminate ligand framework to elucidate the effect of ligand structure on the rate and selectivity of olefin/1,3-diene and cyclic ester polymerization, with small ligand changes having a large impact on the resulting polymerizations. Generation of the active cationic species was easily streamlined by identification of appropriate catalyst : organoborate ratios, allowing for high catalyst efficiencies. Notably, we demonstrate the first cationic rare earth metal alkyl-initiated polymerization of δ-valerolactone and ε-decalactone as well as introduced five new block copolymer morphologies. In addition, selective degradation of the ester block in poly(isoprene-b-caprolactone) enabled recovery of the polyisoprene block with identical spectroscopic and thermal properties. Significantly, recopolymerization of the recovered poly(1,3-diene) with fresh ε-caprolactone reproduced the desired diblocks with nearly identical thermal and physical properties to those of virgin copolymer, illustrating a plausible recycling scheme for these materials.

Ligand features that promote one-pot block copolymerization of 1,3-dienes and cyclic esters were realized with yttrium β-diketiminate complexes. Depolymerization and repolymerization of the polyester block introduced a plausible recycling strategy.

One-Pot Synthesis of Alternating (Ultra-High Molecular Weight) Multiblock Copolymers via a Combination of Anionic Polymerization and Polycondensation

This article presents a fast, straightforward synthesis approach to polymerize alternating multiblock copolymers, ultra-high molecular weight (UHMW) (homo)polymers as well as precursors for complex macromolecular topologies such as comb or barbwire architectures. The one-pot synthesis strategy proposed in this work is based on anionic polymerization via a bifunctional initiator and the subsequent linking of macro dianions with a bifunctional linker, additionally overcoming the limitations associated with the monomer reactivity. Thus, the synthetic route guarantees the repeating size of polymer blocks and an equal distribution of functional groups in precursors for complex topologies. Dianions of polystyrene (PS), polyisoprene-b-polystyrene-b-polyisoprene, and poly-2-vinylpyridine-b-polystyrene-b-poly-2-vinylpyridine are linked with α , α ' -dibromo-para-xylene to UHMW and multiblock copolymers. Multiblock copolymers with on average up to 50 well-defined alternating A and B blocks are accessible within 15 min.

Half-sandwich scandium dibenzyl complexes bearing penta- or tetra-arylcyclopentadienyl ligands: synthesis, structure and syndiospecific styrene polymerization activity

A series of half-sandwich scandium dibenzyl complexes has been synthesized via a reaction of KCp^(Ar*)5 or KCp^Ar5 (Ar* = 3,5-^tBu₂–C₆H₃; Ar = 3,5-ⁱPr₂–C₆H₃) or KCp^(Ar*)4H, KCp^Ar4H and KCp^Ph4H with the cationic scandium complex [Sc(p-CH₂C₆H₄-Me)₂(THF)_x][BPh₄].