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. We discuss advancements in heteroatom tolerant coordination–insertion polymerizations, methods of controlling radical polymerizations to incorporate olefinic monomers, as well as combined approaches employing sequential polymerizations. Finally, we discuss state‐of‐the‐art stimuli‐responsive systems capable of facile switching between catalytic pathways and provide an outlook towards applications in which tailored copolymers are ideally suited.

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.

We detail a polymer synthetic methodology that merges the techniques of insertion and radical polymerization methods into a single organometallic catalyst. This metal–organic insertion/light initiated radical (MILRad) polymerization technique proves successful at polymerizing methyl acrylate (MA) and hexene, using light as a critical stimulus to activate the dormant photoresponsive nature of the insertion catalyst. In this study, we describe a novel approach that uses visible light (460 nm) to switch the catalytic activity of a cationic palladium catalyst from an insertion route to a radical process when desired. We discovered that in a mixture of MA and hexene one monomer can be selectively polymerized using light and dark cycles, respectively. As a result, this polymerization process enables the copolymerization of MA and hexene to create homo- and block copolymer architectures facilitated solely by visible light. In this work, we show the synthesis of MA homopolymers in molecular weight ranges (M n 50–400 kDa) with dispersities of ∼1.7. Synthesis of MA (A) and hexene (B) block copolymers were accomplished with a single catalyst in both a sequential and novel one-pot approach, relying solely upon visible light irradiation. A series of BA block copolymers were prepared with tunable monomer compositions, molecular weight ranges of (M n 11–36 kDa), and well-controlled polydispersities (∼1.3–1.6) in a robust rapid synthesis. MILRad polymerization circumvents the need for quantitative conversions during block formation afforded by the orthogonal monomer reactivity dependent upon a light stimulus to acquire distinct polymer architectures with variable block compositions. The use of a photocontrollable “switch” affecting a single organometallic catalyst allows access to block polymers from nonpolar and polar olefins in a novel and facile approach.

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.

The photoinitiated radical polymerization pathway of MILRad polymerization towards its ability to polymerize a variety of vinyl polar functional monomers is investigated.