Di- and Triblock Copolymers Based on Polyethylene and Polyisobutene Blocks. Toward New Thermoplastic Elastomers

Coordinative Chain Transfer and Chain Shuttling Polymerization

Coordinative chain transfer polymerization, CCTP, is a degenerative chain transfer polymerization process that has a wide range of applications. It allows a highly controlled synthesis of polyolefins, stereoregular polydienes, and stereoregular polystyrene, including (stereo)block as well as statistical copolymers thereof. It also shows a green character by allowing catalyst economy during the synthesis of such polymers. CCTP notably allows the end functionalization of both the commodity and stereoregular specialty polymers aforementionned, control of the composition of statistical copolymers without adjusting the feed, and quantitative formation of 1-alkenes from ethene. A one-pot one-step synthesis of the original multiblock microstructures and architectures by chain shuttling polymerization (CSP) is also an asset of CCTP. This methodology takes advantage of the simultaneous presence of two catalysts of different selectivity toward comonomers that produce blocks of different composition/microstructure, while still allowing the chain transfer. This affords the production of highly performant functional polymers, such as thermoplastic elastomers and adhesives, among others. This approach has been extended to cyclic esters' and ethers' ring-opening polymerization, providing new types of multiblock microstructure. The present Review provides the state of the art in the field with a focus on the last 10 years.

Block Copolymer Synthesis by the Combination of Living Cationic Polymerization and Other Polymerization Methods

The foremost limitation of block copolymer synthesis is to polymerize two or more different types of monomers with different reactivity profiles using a single polymerization technique. Controlled living polymerization techniques play a vital role in the preparation of wide range of block copolymers, thus are revolutionary techniques for polymer industry. Polymers with good control over molecular weight, molecular weight distribution, chain-end functionality and architectures can be prepared by these processes. In order to improve the existing applications and create new opportunities to design a new block copolymer system with improved physical and chemical properties, the combination of two different polymerization techniques have tremendous scope. Such kinds of macromolecules may be attended by combination of homopolymerization of different monomers by post-modification techniques using a macroinitiator or by using a dual initiator which allows the combination of two mechanistically distinct techniques. This review focuses on recent advances in synthesis of block copolymers by combination of living cationic polymerization with other polymerization techniques and click chemistry.

Modulation of side chain crystallinity in alternating copolymers

A remarkable enhancement in crystalline melting temperature (T_m) was observed in a series of fatty acids and mPEG containing alternating copolymers with the lone increase in mPEG chain lengths.

Ultra-high molecular weight elastomeric polyethylene using an electronically and sterically enhanced nickel catalyst

Highly active para-t-Bu-containing 1,2-bis(imino)acenaphthene-Ni(ii) catalysts are disclosed which afford hyper-branched PEs with M_w's up to 3.1 × 10⁶ g mol⁻¹; high tensile strength, excellent shape fixity as well as high elongation at break are a feature.

Elastomeric polyethylenes accessible via ethylene homo-polymerization using an unsymmetrical α-diimino-nickel catalyst

Elastomeric polyethylenes, with good elastic recovery and high elongation at break, have been prepared using a new family of unsymmetrical α-diimino-nickel catalysts that display high activities and high thermal stability.

Polyethylene-g-Polystyrene Copolymers by Combination of ROMP, Mn2(CO)10-Assisted TEMPO Substitution and NMRP

The synthesis of polyethylene-graft-polystyrene copolymers by a multistep "grafting from" approach is described. In the first step, a bromo-functional polyethylene (PE-Br) was synthesized via ring-opening metathesis polymerization (ROMP) of cis-cyclooctene (COE) and quantitative hydrobromination. Subsequent irradiation of PE-Br under visible light in the presence of dimanganese decacarbonyl (Mn₂(CO)₁₀) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) resulted in the formation of TEMPO-substituted polyethylene (PE-TEMPO). Polystyrene (PS) chains were then grown via nitroxide mediated radical polymerization (NMRP) from the PE-TEMPO precursor to give desired PE-g-PS copolymers in a controlled manner. The intermediates at each step and final graft copolymers were characterized by ¹H NMR, FT-IR, GPC, and DSC analyses.

Self-assembly of well-defined fatty acid based amphiphilic thermoresponsive random copolymers

Side-chain stearic acid containing thermoresponsive and crystalline random copolymers are synthesized via RAFT technique, which self-assembled to spherical micellar structures in aqueous solution depending on stearate content in the copolymer.

Multiblock Copolymers by Thiol Addition Across Norbornene

Multiblock copolymers, composed of different combinations and number of blocks, offer appreciable opportunities for new advanced materials. However, exploring this parameter space using traditional block copolymer synthetic techniques, such as living polymerization of sequential blocks, is time-consuming and requires stringent conditions. Using thiol addition across norbornene chemistry, we demonstrate a simple synthetic approach to multiblock copolymers that produces either random or alternating architectures, depending on the choice of reactants. Past reports have highlighted the challenges associated with using thiol-ene chemistry for polymer-polymer conjugation; however, using norbornene as the "ene" yielded multiblock copolymers at least four or five blocks. Preparation of new multiblock copolymers containing two or three block chemistries highlights the versatility of this new approach. These materials were thermally stable and showed microphase separation according to characterization by DSC, SAXS, and AFM. This chemical platform offers a facile and efficient route to exploring the many possibilities of multiblock copolymers.