Linear Block Copolymer Synthesis.

Block copolymers form the basis of the most ubiquitous materials such as thermoplastic elastomers, bridge interphases in polymer blends, and are fundamental for the development of high-performance materials. The driving force to further advance these materials is the accessibility of block copolymers, which have a wide variety in composition, functional group content, and precision of their structure. To advance and broaden the application of block copolymers will depend on the nature of combined segmented blocks, guided through the combination of polymerization techniques to reach a high versatility in block copolymer architecture and function.

Dual Polymerization Pathway for Polyolefin-Polar Block Copolymer Synthesis via MILRad: Mechanism and Scope.

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.

Switching the Reactivity of Palladium Diimines with "Ancillary" Ligand to Select between Olefin Polymerization, Branching Regulation, or Olefin Isomerization.

Coordinating solvents are commonly employed as ancillary ligands to stabilize late transition metal complexes and are conventionally considered to have little effect on the reaction products. Our work identifies that the presence of ancillary ligand in Pd-diimine catalyzed polymerizations of α-olefins can drastically alter reactivity. The addition of different amounts of acetonitrile allows for switching between distinct reaction modes: isomerization-polymerization with high branching (0 equiv.

Branching Regulation in Olefin Polymerization via Lewis Acid Triggered Isomerization of Monomers.

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.

Olefins and Vinyl Polar Monomers: Bridging the Gap for Next Generation Materials.

The inherent differences in reactivity between activated and non-activated alkenes prevents copolymerization using established polymer synthesis techniques. Research over the past 20 years has greatly advanced the copolymerization of polar vinyl monomers and olefins. This Review highlights the challenges associated with conventional polymerization systems and evaluates the most relevant methods which have been developed to "bridge the gap" between polar vinyl monomers and olefins.