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Construction of CO2‐based amphiphilic block copolymers (ABCs) is an efficient method for providing CO2‐based polycarbonates with self‐assembly properties in aqueous media. It is challenging to construct CO2‐based ABCs by one‐step strategies from mixed monomers because hydrophilic blocks, usually composed of polar monomers, have negative effects on the synthesis of polycarbonates. In this work, we report a one‐step method to construct CO2‐based ABCs obtained by simultaneous ring‐opening copolymerization (ROCOP) of CO2/epoxides and reversible addition‐fragmentation chain transfer (RAFT) polymerization of N‐isopropyl acrylamide (NIPAM). A trithiocarbonate/carboxy compound was used as the bifunctional chain transfer agent, and an aluminum porphyrin complex was used as the catalyst for ROCOP, which proved to be efficient in CO2 copolymerization even in the presence of NIPAM with strong polarity. This strategy allows flexible control over the molecular weight (5–16 kg/mol) and the hydrophilic‐hydrophobic balance (HLB 9–18) of the ABCs, and ensures narrow polydispersity Đ (1.1–1.3) of the polymers. The ABCs can further self‐assemble into micelles in water with controllable diameters and reversible phase transformation behavior with temperature changes from 25 to 40 °C. This simple route to CO2‐based ABCs with multiple functions has large potential in biomedical applications. [ABSTRACT FROM AUTHOR]

A series of vanadium(V) aroylhydrazine‐arylolates is employed in ethylene polymerization to produce ultra‐high molecular weight polyethylene (UHMWPE), surprisingly extending to such coupling reactions beyond their common usage in the oxidation of hexanes and alcohols. Activated by either MAO or DMAC, the complexes V1–V3 efficiently catalyze the polymerization of ethylene into UHMWPE, that is, with an activity up to 3.37 × 106 g mol−1 h−1 (60°C) and the polyethylene obtained has a molecular weight around 3 million g mol−1, being the highest molecular weight achieved by a vanadium catalyst so far. More importantly, the significant effects of different cocatalysts are well illustrated; the catalytic system with MAO generally shows lower activity with almost one order in the magnitude than that with DMAC (0.43 vs. 3.37 × 106 g mol−1 h−1), but the polyethylenes with higher molecular weights are obtained by the system with MAO. [ABSTRACT FROM AUTHOR]

Six examples of newly synthesized α,α'‐bis (aryl)‐2,3:5,6‐bis (pentame thylene)pyridyliron complexes [2,3:5,6‐{C4H8C(NAr)}2C5HN]FeCl2 (Ar = 2‐(c‐C5H9)‐6‐MeC6H3Fe1, 2‐(c‐C6H11)‐6‐MeC6H3Fe2, 2‐(c‐C8H15)‐6‐MeC6H3Fe3, 2‐(c‐C5H9)‐4,6‐Me2C6H2Fe4, 2‐(c‐C6H11)‐4,6‐Me2C6H2Fe5, 2‐(c‐C8H15)‐4,6‐Me2C6H2Fe6; c refers as cyclic), on activation with methylalumoxane (MAO) or modified MAO (MMAO), exhibit high activities towards ethylene polymerization, producing strictly linear polyethylenes with terminal vinyl groups. The catalytic performances are systematically investigated along with various polymerization parameters as well as the microstructures of resultant polyethylenes. The steric hindrances of ortho‐cycloalkyl substituents of Nimino‐aryl groups significantly affect the activities of the corresponding iron precatalysts as well as the microstructures of resultant polyethylenes: higher steric hindrance the ortho‐cycloalkyl substituents, higher activity the iron precatalyst, lower molecular weight the resultant polyethylenes. Experimental observations are additionally supported by the computational study. The resultant polyethylenes exhibited excellent hydrophobicity. [ABSTRACT FROM AUTHOR]

ABSTRACT A series of 2-(arylimino)benzylidene-9-arylimino-5,6,7,8-tetrahydrocyclohepta [b]pyridyliron(II) chlorides was synthesized and characterized using FT-IR and elemental analysis, and the molecular structures of complexes Fe3 and Fe4 have been confirmed by the single-crystal X-ray diffraction as a pseudo-square-pyramidal or distorted trigonal-bipyramidal geometry around the iron core. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all iron precatalysts exhibited high activities toward ethylene polymerization with a marvelous thermo-stability and long lifetime. The Fe4/MAO system showed highest activity of 1.56 × 107 gPE·mol−1(Fe)·h−1 at 70 °C, which is one of the highest activities toward ethylene polymerization by iron precatalysts. Even up to 80 °C, Fe3/MAO system still persist high activity as 6.87 × 106 g(PE)·mol−1(Fe)·h−1, demonstrating remarkable thermal stability for industrial polymerizations (80-100 °C). This was mainly attributing to the phenyl modification of the framework of the iron precatalysts. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 830-842 [ABSTRACT FROM AUTHOR]

The unsymmetrical bis (arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC6H4)2CH}2–4‐t‐BuC6H2}]‐6‐(CMeNAr)C5H3N (Ar = 2,6‐Me2C6H3L1, 2,6‐Et2C6H3L2, 2,6‐i‐Pr2C6H3L3, 2,4,6‐Me3C6H2L4, 2,6‐Et2–4‐MeC6H2L5), each containing one N‐aryl group bedecked with ortho‐substituted fluorobenzhydryl groups, have been employed in the preparation of the corresponding five‐coordinate cobalt (II) chelates, LCoCl2 (Co1 – Co5); the symmetrical comparator [2,6‐{CMeN(2,6‐(4‐FC6H4)2CH)2–4‐t‐BuC6H2}2C5H3N]CoCl2 (Co6) is also reported. All cobaltous complexes are paramagnetic and have been characterized by 1H/19F NMR spectroscopy, FT‐IR spectroscopy and elemental analysis. The molecular structures of Co3 and Co6 highlight the different degrees of steric protection given to the metal center by the particular N‐aryl group combination. Depending on the aluminoxane co‐catalyst employed to activate the cobalt precatalyst, distinct variations in thermal stability and activity of the catalyst towards ethylene polymerization were exhibited. In particular with MAO, the resultant catalysts reached their optimal performance at 70 °C delivering high activities of up to 10.1 × 106 g PE (mol of Co)−1 h−1 with Co1 > Co4 > Co2 > Co5 > Co3 >> Co6. On the other hand, using MMAO, the catalysts operate most effectively at 30 °C but are by comparison less productive. In general, the polyethylenes were highly linear, narrowly disperse and displayed a wide range of molecular weights [Mw range: 18.5–58.7 kg mol−1 (MAO); 206.1–352.5 kg mol−1 (MMAO)]. [ABSTRACT FROM AUTHOR]