Late Transition Metal Catalysts with Chelating Amines for Olefin Polymerization

Polyolefins are the most consumed polymeric materials extensively used in our daily life and are usually generated by coordination polymerization in the polyolefin industry. Olefin polymerization catalysts containing transition metal–organic compound combinations are undoubtedly crucial for the development of the polyolefin industry. The nitrogen donor atom has attracted considerable interest and is widely used in combination with the transition metal for the fine-tuning of the chemical environment around the metal center. In addition to widely reported olefin polymerization catalysts with imine and amide donors (sp2 hybrid N), late transition metal catalysts with chelating amine donors (sp3 hybrid N) for olefin polymerization have never been reviewed. In this review paper, we focus on late transition metal (Ni, Pd, Fe, and Co) catalysts with chelating amines for olefin polymerization. A variety of late transition metal catalysts bearing different neutral amine donors are surveyed for olefin polymerization, including amine–imine, amine–pyridine, α-diamine, and [N, N, N] tridentate ligands with amine donors. The relationship between catalyst structure and catalytic performance is also encompassed. This review aims to promote the design of late transition metal catalysts with unique chelating amine donors for the development of high-performance polyolefin materials.

Vesicular assemblies of thermoresponsive amphiphilic polypeptide copolymers for guest encapsulation and release

Thermoresponsive amphiphilic polypeptide copolymers are synthesized via different polymerization techniques for their self-assembly into vesicular aggregates for guest encapsulation and release.

Amine–imine palladium catalysts for living polymerization of ethylene and copolymerization of ethylene with methyl acrylate: incorporation of acrylate units into the main chain and branch end

A bulky amine–imine palladium catalyst can polymerize ethylene in a living fashion. Copolymerizations of ethylene and methyl acrylate afford branched copolymers with terminal and main chain acrylate units.

Dual-responsive polypseudorotaxanes based on block-selected inclusion between polyethylene-block-poly(ethylene glycol) diblock copolymers and 1,4-diethoxypillar[5]arene

Based on the selective recognition of the polyethylene (PE) block of polyethylene-block-poly(ethylene glycol) (PE-b-PEG) by 1,4-diethoxypillar[5]arene (DEP5A), two novel thermo and competitive guest (1,4-dibromobutane or hexanedinitrile) responsive polypseudorotaxanes (PPRs) have been successfully constructed. The formation of PPRs both in solution and in the solid state was demonstrated by (1)H NMR, 2D NOESY, and WAXD analyses. TGA data illustrate that PPRs exhibit higher thermal stability than their precursor diblock copolymers. Moreover, intriguing porous disk-like aggregates are produced by electrospraying of PPRs in CHCl3 and the self-assembled structures of PPRs are totally changed by the addition of 1,4-dibromobutane or hexanedinitrile, demonstrating their competitive guest stimuli-responsiveness.

Synthesis, characterization and micellization of amphiphilic polyethylene-b-polyphosphoester block copolymers

Amphiphilic polyethylene-block-polyphosphoester (PE-b-PPE) copolymers can self-assemble into spherical micelles in aqueous solution and efficiently carry paclitaxel (PTX) drug.

Synthesis, micellization, and thermally-induced macroscopic micelle aggregation of poly(vinyl chloride)-g-poly(N-isopropylacrylamide) amphiphilic copolymer

PVC-g-PNIPAM amphiphilic copolymers with controlled graft lengths and densities are synthesized, which form unique macroscopic aggregates with well-defined 3D shapes in dilute aqueous solution above the LCST.

Thermoresponsive self-assembly of nanostructures from a collagen-like peptide-containing diblock copolymer

Temperature-triggered formation of nanostructures with distinct biological activity offers opportunities in selective modification of matrices and in drug delivery. Toward these ends, diblock polymers comprising poly(diethylene glycol methyl ether methacrylate) (PDEGMEMA) conjugated to a triple helix-forming collagen-like peptide were produced. Triggered by the collapse of the thermoresponsive domain above its LCST, the conjugate undergoes a reversible transition in aqueous solution to form well-defined nanovesicles with diameters of approximately 100 nm, with a transition temperature of 37 °C. The incorporation of CLP domains in these nanostructures may offer opportunities for the selective targeting of collagen-containing matrices.