203930-85-2Relevant academic research and scientific papers
Branching Regulation in Olefin Polymerization via Lewis Acid Triggered Isomerization of Monomers
Basbug Alhan, Hatice E.,Harth, Eva,Jones, Glen R.
, p. 4743 - 4749 (2020)
We present a new strategy to regulate branching in chain-walking olefin polymerization by triggering a rapid isomerization of 1-alkene monomers into internal olefins by adding a Lewis acid. Polymerization of internal alkenes proceeds via chain-walking to give polymers with much higher branching than 1-alkene analogues. The utility of this approach is exemplified by synthesis of well-defined block copolymers with distinct branching characteristics per block by addition of Lewis acid midway through a reaction. We propose a novel mechanism whereby Lewis acid undergoes a counterion swap with the complex which favors isomerization as well as forming adducts with ancillary ligands, freeing coordination sites for internal alkene coordination polymerization.
Dual Polymerization Pathway for Polyolefin-Polar Block Copolymer Synthesis via MILRad: Mechanism and Scope
Dau, Huong,Keyes, Anthony,Basbug Alhan, Hatice E.,Ordonez, Estela,Tsogtgerel, Enkhjargal,Gies, Anthony P.,Auyeung, Evelyn,Zhou, Zhe,Maity, Asim,Das, Anuvab,Powers, David C.,Beezer, Dain B.,Harth, Eva
supporting information, p. 21469 - 21483 (2020/12/21)
This work explores the mechanism whereby a cationic diimine Pd(II) complex combines coordination insertion and radical polymerization to form polyolefin-polar block copolymers. The initial requirement involves the insertion of a single acrylate monomer into the Pd(II)-polyolefin intermediates, which generate a stable polymeric chelate through a chain-walking mechanism. This thermodynamically stable chelate was also found to be photochemically inactive, and a unique mechanism was discovered which allows for radical polymerization. Rate-determining opening of the chelate by an ancillary ligand followed by additional chain walking allows the metal to migrate to the α-carbon of the acrylate moiety. Ultimately, the molecular parameters necessary for blue-light-triggered Pd-C bond homolysis from this α-carbon to form a carbon-centered macroradical species were established. This intermediate is understood to initiate free radical polymerization of acrylic monomers, thereby facilitating block copolymer synthesis from a single Pd(II) complex. Key intermediates were isolated and comprehensively characterized through exhaustive analytical methods which detail the mechanism while confirming the structural integrity of the polyolefin-polar blocks. Chain walking combined with blue-light irradiation functions as the mechanistic switch from coordination insertion to radical polymerization. On the basis of these discoveries, robust di- and triblock copolymer syntheses have been demonstrated with olefins (ethylene and 1-hexene) which produce amorphous or crystalline blocks and acrylics (methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate) in broad molecular weight ranges and compositions, yielding AB diblocks and BAB triblocks.
