Recent Advances in Nickel Catalysts with Industrial Exploitability for Copolymerization of Ethylene with Polar Monomers.

The direct copolymerization of ethylene with polar monomers to produce functional polyolefins continues to be highly appealing due to its simple operation process and controllable product microstructure. Low-cost nickel catalysts have been extensively utilized in academia for the synthesis of polar polyethylenes. However, the development of high-temperature copolymerization catalysts suitable for industrial production conditions remains a significant challenge. Classified by the resultant copolymers, this review provides a comprehensive summary of the research progress in nickel complex catalyzed ethylene-polar monomer copolymerization at elevated temperatures in the past five years. The polymerization results of ethylene-methyl acrylate copolymers, ethylene-tert-butyl acrylate copolymers, ethylene-other fundamental polar monomer copolymers, and ethylene-special polar monomer copolymers are thoroughly summarized. The involved nickel catalysts include the phosphine-phenolate type, bisphosphine-monoxide type, phosphine-carbonyl type, phosphine-benzenamine type, and the phosphine-enolate type. The effective modulation of catalytic activity, molecular weight, molecular weight distribution, melting point, and polar monomer incorporation ratio by these catalysts is concluded and discussed. It reveals that the optimization of the catalyst system is mainly achieved through the methods of catalyst structure rational design, extra additive introduction, and single-site catalyst heterogenization. As a result, some outstanding catalysts are capable of producing polar polyethylenes that closely resemble commercial products. To achieve industrialization, it is essential to further emphasize the fundamental science of high-temperature copolymerization systems and the application performance of resultant polar polyethylenes.

Recent Advances in the Copolymerization of Ethylene with Polar Comonomers by Nickel Catalysts.

The less-expensive and earth-abundant nickel catalyst is highly promising in the copolymerization of ethylene with polar monomers and has thus attracted increasing attention in both industry and academia. Herein, we have summarized the recent advancements made in the state-of-the-art nickel catalysts with different types of ligands for ethylene copolymerization and how these modifications influence the catalyst performance, as well as new polymerization modulation strategies. With regard to α-diimine, salicylaldimine/ketoiminato, phosphino-phenolate, phosphine-sulfonate, bisphospnine monoxide, N-heterocyclic carbene and other unclassified chelates, the properties of each catalyst and fine modulation of key copolymerization parameters (activity, molecular weight, comonomer incorporation rate, etc.) are revealed in detail. Despite significant achievements, many opportunities and possibilities are yet to be fully addressed, and a brief outlook on the future development and long-standing challenges is provided.

Precipitation Polymerization: A Powerful Tool for Preparation of Uniform Polymer Particles.

Precipitation polymerization (PP) is a powerful tool to prepare various types of uniform polymer particles owing to its outstanding advantages of easy operation and the absence of any surfactant. Several PP approaches have been developed up to now, including traditional thermo-induced precipitation polymerization (TRPP), distillation precipitation polymerization (DPP), reflux precipitation polymerization (RPP), photoinduced precipitation polymerization (PPP), solvothermal precipitation polymerization (SPP), controlled/''living'' radical precipitation polymerization (CRPP) and self-stabilized precipitation polymerization (2SPP). In this review, a general introduction to the categories, mechanisms, and applications of precipitation polymerization and the recent developments are presented, proving that PP has great potential to become one of the most attractive polymerization techniques in materials science and bio-medical areas.

Enhancing Ethylene Polymerization of NNN-Cobalt(II) Precatalysts Adorned with a Fluoro-substituent.

Unsymmetrical 2-(1-(2,4-dibenzhydryl-6-fluorophenylimino)ethyl)-6-(1-alkylphenyl-imino)ethyl)pyridine compounds (Ar = 2,6-Me2C6H3 in L1; 2,6-Et2C6H3 in L2; 2,6- i Pr2C6H3 in L3; 2,4,6-Me3C6H2 in L4; 2,6-Et2-4-Me-C6H2 in L5) were prepared and characterized. The treatment of CoCl2 with the compounds L1-L5 afforded the corresponding cobalt complexes Co1-Co5 in excellent yields. The molecular structures of Co3 and Co4 were determined by single-crystal X-ray diffraction, revealing the distorted-square-pyramidal geometry with three nitrogen atoms and two chlorine atoms around the cobalt center. Compared with previous bis(imino)pyridylcobalt analogues, all of the cobalt precatalysts displayed exceptionally higher activities toward ethylene polymerization with 1.32 × 107 g (PE) mol-1 (Co) h-1 at 60 °C in the presence of a co-catalyst MAO or MMAO. These cobalt catalysts produced highly linear polyethylene (PE) waxes with vinyl end groups and low molecular weight (M w up to 8.23 kg mol-1) along with a relatively lower melting point (all-round T ms < 128 °C). The narrow dispersity of resultant polyethylenes indicated the single-site active species of the catalytic system.

Simulated Patient Role-Plays with Consumers with Lived Experience of Mental Illness Post-Mental Health First Aid Training: Interrater and Test Re-Test Reliability of an Observed Behavioral Assessment Rubric.

Mental Health First Aid (MHFA) training teaches participants how to assist people experiencing mental health problems and crises. Observed behavioral assessments, post-training, are lacking, and the literature largely focuses on self-reported measurement of behaviors and confidence. This study explores the reliability of an observed behavioral assessment rubric used to assess pharmacy students during simulated patient (SP) role-play assessments with mental health consumers. Post-MHFA training, pharmacy students (n = 528) participated in SP role-play assessments (n = 96) of six mental health cases enacted by consumers with lived experience of mental illness. Each assessment was marked by the tutor, participating student, and consumer (three raters). Non-parametric tests were used to compare raters' means scores and pass/fail categories. Interrater reliability analyses were conducted for overall scores, as well as pass/fail categories using intra-class correlation coefficient (ICC) and Fleiss' Kappa, respectively. Test re-test reliability analyses were conducted using Pearson's correlation. For interrater reliability analyses, the intra-class correlation coefficient varied from poor-to-good to moderate-to-excellent for individual cases but was moderate-to-excellent for combined cases (0.70; CI 0.58-0.80). Fleiss' Kappa varied across cases but was fair-to-good for combined cases (0.57, p < 0.001). For test re-test reliability analyses, Pearson's correlation was strong for individual and combined cases (0.87; p < 0.001). Recommended modifications to the rubric, including the addition of barrier items, scoring guides, and specific examples, as well as the creation of new case-specific rubric versions, may improve reliability. The rubric can be used to facilitate the measurement of actual, observed behaviors post-MHFA training in pharmacy and other health care curricula.

Sterically and Electronically Modified Aryliminopyridyl-Nickel Bromide Precatalysts for an Access to Branched Polyethylene with Vinyl/Vinylene End Groups.

A series of 2-((arylimino)ethyl)pyridine derivatives (L1-L5), each containing N-2,4-bis(dibenzocycloheptyl) groups with variations in the steric/electronic properties of the ortho-substituent in the aryl ring, and the corresponding nickel bromide precatalysts [2-N{2,4-(C15H13)-6-R-C6H2}C7H7N]NiBr2 (R = Me (Ni1), Et (Ni2), i-Pr (Ni3), Cl (Ni4), or F (Ni5)), have been prepared in high yield. All the precatalysts are air-stable and characterized by Fourier transform infrared spectroscopy and elemental analysis. The molecular structures of Ni2 and Ni5 were proved through single-crystal X-ray diffraction analysis. The steric/electronic impact of the catalysts on ethylene polymerization and the resulting polymer properties were studied. Upon activation with either MAO or EASC, all the complexes displayed higher activities (up to 7.93 × 106 g of PE (mol of Ni)-1 h-1 with MAO) in ethylene polymerization and produced moderate to highly branched unsaturated polyethylene with a molecular weight of up to 16.55 kg/mol with narrow dispersities (1.6-2.4). Significantly, the generated polyethylenes are branched and unsaturated with a major class of internal double bond (-CH=CH-) as compared to the terminal double bond (-CH=CH2) (vinylene/vinyl = 9.8:1 to 1.8:1). Notably, their catalytic activities, types of unsaturation, and branches are highly affected by the nature of the ortho-substituent and reaction temperature. Moreover, the precatalysts Ni4 and Ni5 (with N-ortho = Cl and F) exhibited lower catalytic activities, produced low-molecular-weight polyethylene with a high melt temperature and the least number of branches with an increased level of terminal double bonds.

4,4'-Difluorobenzhydryl-modified bis(imino)-pyridyliron(ii) chlorides as thermally stable precatalysts for strictly linear polyethylenes with narrow dispersities.

The 4,4'-difluorobenzhydryl-modified bis(imino)pyridylferrous chlorides, [2-{CMeN(2,6-(4-FC6H4)2CH2-4-t-BuC6H2)}-6-(CMeNAr)C5H3N] FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-i-Pr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, 2,6-Et-4-MeC6H2Fe5 and 2,6-(4-FC6H4)2CH2-4-t-BuC6H2Fe6), were synthesized in good yields. All iron complexes were characterized by 1H/19F NMR and elemental analysis, and the molecular structures of representative complexes Fe1 and Fe6 were determined by single crystal X-ray diffraction, which revealed a slightly distorted square pyramid around the iron center. Activated with either MAO or MMAO, Fe1-Fe5 exhibited very high activities (up to 17.2 × 106 g (PE) mol-1 (Fe) h-1 for Fe1/MMAO) toward ethylene polymerization, producing highly linear polyethylenes with narrow dispersities as required by industry and value added PEs. Importantly, the Fe1/MAO maintained an activity of 9.5 × 106 g (PE) mol-1 (Fe) h-1 at 100 °C of operating temperature, making the catalytic system suitable for practical application. Simulation quantitatively revealed the mechanism of the enhanced catalytic performance from the electronic and steric point of view.

Steric and electronic modulation of iron catalysts as a route to remarkably high molecular weight linear polyethylenes.

Five structurally related bis(arylimino)pyridine-iron(ii) chloride complexes, [2-[CMeN{2,6-{(4-FC6H4)2CH}2-4-NO2}]-6-(CMeNAr)C5H3N]FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-i-Pr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, and 2,6-Et2-4-MeC6H2Fe5), incorporating one N-2,6-bis{di(4-fluorophenyl)methyl}-4-nitrophenyl group and one distinct N-aryl group, have been prepared in good yield through the interaction of the corresponding free ligands (L1-L5) with FeCl2·4H2O. All ferrous complexes were paramagnetic which was manifested by broad and highly shifted peaks in their 1H NMR spectra. The marked steric imbalance imposed by the two inequivalent N-aryl groups was a key feature highlighted in the molecular structures of representative complexes Fe1 and Fe2. Upon activation with either MAO or MMAO, Fe1-Fe5 all exhibited high activities for ethylene polymerization with good thermal stability [activities as high as 1.58 × 107 g (PE) mol-1 (Fe) h-1 at 60 °C], affording especially high molecular weight linear polyethylenes (3.92 × 105 g mol-1 at 70 °C; Tm > 130 °C). To the best of our knowledge, the molecular weights of the polyethylenes produced by the current class of iron catalysts exceed the highest values reported for related bis(imino)pyridine-iron catalysts to date; changes in the ortho-R1 substitution pattern offered some additional fine control of the molecular weight. Moreover, the nature of the aluminoxane co-catalyst employed had a noticeable effect on the polymer end group composition. When using MAO, unsaturated polymers containing both vinyl and n-propyl end groups were evident, whereas with MMAO, fully saturated polymers were generated containing both isobutyl and n-propyl end groups.

1,5-Naphthyl-linked bis(imino)pyridines as binucleating scaffolds for dicobalt ethylene oligo-/polymerization catalysts: exploring temperature and steric effects.

Six examples of dinuclear bis(imino)pyridine-cobalt(ii) complexes, [1,5-{2-(CMe[double bond, length as m-dash]N)-6-(CMe[double bond, length as m-dash]N(2,6-R12-4-R2-C6H2))C5H3N}2(C10H6)]Co2Cl4 (R1 = Me, R2 = H Co1; R1 = Et, R2 = H Co2; R1 = iPr, R2 = H Co3; R1 = Me, R2 = Me Co4; R1 = Et, R2 = Me Co5; R1 = CHPh2, R2 = Me Co6), have been prepared from the corresponding bis(tridentate) compartmental ligands (L1-L6) in reasonable yields. The molecular structures of Co3 and Co5 revealed two N,N,N-cobalt dichloride units to adopt anti-positions about the 1,5-naphthyl linking unit, with each cobalt center exhibiting a distorted trigonal bipyramidal geometry. On activation with either MAO or MMAO, Co1-Co6 were shown to promote both polymerization and oligomerization of ethylene with high overall activities (up to 1.03 × 107 gPE per·mol(Co) per·h for Co1/MAO at 70 °C). Curiously, on increasing the reaction temperature a larger proportion of polymer was noted, while at lower temperature an enhanced selectivity for oligomer was seen. In general, the oligomeric products displayed Schulz-Flory distributions with high selectivities for α-olefins (>99%). On the other hand, the highly linear polymers displayed narrow dispersities and comprised both fully saturated and unsaturated chain ends with the vinyl content (-CH[double bond, length as m-dash]CH2) found to rise with the reaction temperature. By modulating the steric hindrance exerted by the ortho-R1 substituents in the precatalyst, polyethylenes displaying a remarkably broad range of molecular weights could be obtained [from 4.52 kg mol-1 (R1 = Me) to 246.7 kg mol-1 (R1 = CHPh2)].

gem-Dimethyl-substituted bis(imino)dihydroquinolines as thermally stable supports for highly active cobalt catalysts that produce linear PE waxes.

Six types of 2,8-bis(imino)-7,7-dimethyl-5,6-dihydroquinoline, 2-(ArN[double bond, length as m-dash]CMe)-8-(ArN)-7,7-Me2C9H6N (Ar = 2,6-Me2C6H3L1, 2,6-Et2C6H3L2, 2,6-iPr2C6H3L3, 2,4,6-Me3C6H2L4, 2,6-Et2-4-MeC6H2L5, 2,4,6-tBu3C6H3L6), distinguishable by their steric and electronic profile, are described that can readily undergo complexation with cobaltous chloride to form their corresponding LCoCl2 chelates, Co1-Co6. The molecular structures of Co2 and Co3 reveal square pyramidal geometries with ring puckering a feature of the gem-dimethyl section of their unsymmetrical N,N,N'-ligands. On activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the cobalt complexes exhibited exceptionally high activities for ethylene polymerization with levels reaching up to 1.19 × 107 g PE per mol (Co) per h for mesityl-containing Co4. Significantly, these catalysts exhibited good thermal stability by displaying their optimal performance at temperatures up to 70 °C whilst also maintaining appreciable catalytic lifetimes. With the exception of that obtained using the most sterically hindered Co6 (2,4,6-t-butyl), the polyethylenes are of low molecular weight (Mw≤16.0 kg mol-1) and of narrow dispersity (Mw/Mn≤3.4). Moreover, end-group analysis of these highly linear polymer waxes reveals evidence for unsaturated as well as various levels of fully saturated materials highlighting the role of both ß-H elimination and chain transfer to aluminum as termination pathways.

Plastomeric-like polyethylenes achievable using thermally robust N,N'-nickel catalysts appended with electron withdrawing difluorobenzhydryl and nitro groups.

A new set of five unsymmetrical N,N'-diiminoacenaphthenes, 1-[2,6-{(4-FC6H4)2CH}2-4-NO2C6H4N]-2-(ArN)C2C10H6 (Ar = 2,6-Me2C6H3L1, 2,6-Et2C6H3L2, 2,6-iPr2C6H3L3, 2,4,6-Me3C6H2L4, 2,6-Et2-4-MeC6H2L5), have been synthesized and used to prepare their corresponding nickel(ii) halide complexes, LNiBr2 (Ni1-Ni5) and LNiCl2 (Ni6-Ni10). The molecular structures of Ni3(OH2) and Ni4 reveal distorted square pyramidal and tetrahedral geometries, respectively, while the 1H NMR spectra of all the nickel(ii) (S = 1) complexes show broad paramagnetically shifted peaks. Upon activation with either methylaluminoxane (MAO) or ethylaluminum sesquichloride (Et3Al2Cl2, EASC), Ni1-Ni10 displayed very high activities for ethylene polymerization with the optimal performance being observed using 2,6-dimethyl-containing Ni1 in combination with EASC (1.66 × 107 g PE mol-1 (Ni) h-1 at 50 °C) which produced high molecular weight plastomeric polyethylene (Mw = 3.93 × 105 g mol-1, Tm = 70.6 °C) with narrow dispersity (Mw/Mn = 2.97). Moreover, Ni1/EASC showed good thermal stability by operating effectively at an industrially relevant 80 °C with a level of activity (6.01 × 106 g of PE mol-1 (Ni) h-1) that exceeds previously disclosed N,N'-nickel catalysts under comparable reaction conditions. This improved thermal stability and activity has been ascribed to the combined effects imparted by the para-nitro and fluoride-substituted benzhydryl ortho-substituents.

Adsorption of chloro-anilines from solution by modified peanut husk in fixed-bed column.

Natural peanut husk (NPH) modified with hexadecyl trimethyl ammonium bromide (CTAB) was used as adsorbent to remove 2,5-dimethoxy-4-chloroaniline (DMCH) from solution in a fixed-bed column. Fourier transform infrared spectroscopy analysis and X-ray fluorescence of NPH and modified peanut husk (MPH) showed that CTAB had been introduced onto the surface of NPH. The effects of flow rate and bed depth on breakthrough curves were studied. The Thomas model and the Yan model were selected to fit the column adsorption data and the results showed that the Yan model was better at predicting the breakthrough curves. The adsorption quantity was up to 6.46 mg/g according to the Yan model. The bed depth service time model was used to calculate the critical bed depth from experimental data and it was directly related to flow rate. As a low-cost adsorbent, MPH is promising for the removal of DMCH from solution.