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The α-diimine late transition metal catalyst represents a new strategy for the synthesis of atactic polypropylene elastomer. Taking into account the properties of the material, enhancing the molecular weight of polypropylene at an elevated temperature through modifying the catalyst structure, and further increasing the activity of α-diimine catalyst for propylene polymerization, are urgent problems to be solved. In this work, two α-diimine nickel(II) catalysts with multiple hydroxymethyl phenyl substituents were synthesized and used for propylene homopolymerization. The maximum catalytic activity was 5.40 × 105 gPP/molNi·h, and the activity was still maintained above 105 gPP/molNi·h at 50 °C. The large steric hindrance of catalysts inhibited the chain-walking and chain-transfer reactions, resulting in polypropylene with high molecular weights (407~1101 kg/mol) and low 1,3-enchainment content (3.57~16.96%) in toluene. The low tensile strength (0.3~1.0 MPa), high elongation at break (218~403%) and strain recovery properties (S.R. ~50%, 10 tension cycles) of the resulting polypropylenes, as well as the visible light transmittance of approximately 90%, indicate the characteristics of the transparent elastomer. [ABSTRACT FROM AUTHOR]

Heterogenization of nickel‐based olefin polymerization catalysts has received increasing attention in recent years. In this contribution, positional heterogenization effect in salicylaldimine nickel catalyzed ethylene polymerization is studied. The salicylaldimine nickel pre‐catalysts bearing anchor groups are synthesized, characterized, and investigated in heterogeneous catalytic ethylene polymerization. The anchoring groups are installed at different positions, including the 4‐position of the salicylaldehyde moiety and the 4‐position of the aniline moiety. It is shown that the positions of the anchoring groups have significant effects on heterogeneous ethylene polymerization catalyzed by SiO2‐supported salicylaldimine nickel catalysts. This provides a strategy worth considering for the design of high‐performance heterogeneous catalysts in the future. [ABSTRACT FROM AUTHOR]

In this study, copolymers of 1-butene with allyltrimethylsilane (TMAS) were synthesized via rac-ethylenebis(indenyl)zirconium chloride (rac-Et(Ind)2ZrCl2)/methylaluminoxane (MAO) catalyst. Combining 1H-NMR and Fourier transform infrared (FT-IR) spectroscopies, the microstructure of the copolymer was verified and the insertion rate of TMAS was calculated. Herein, we demonstrate that the isotacticity and thermal decomposition temperature of the copolymers decreased with the contents of allyltrimethylsilane in the copolymers. After blending the resultant copolymers with high isotactic poly(1-butene) powder (HI-PB), it was found that the 1-butene-allyltrimethylsilane copolymer (PB-TMAS) reduced the crystallization temperature, inhibited the formation of form I in the amorphous region at the initial stage of crystal transformation, and slowed down the crystalline transformation from form II to form I, but did not affect the time of the initial reduction of form II. [ABSTRACT FROM AUTHOR]

In this paper, nanorod CeO2 supports were prepared by hydrothermal method using Ce(NO3)3 ⋅ 6H2O as raw material. CuOx/CeO2‐r materials were prepared by calcination using Cu salt‐loaded CeO2‐r supports as raw materials. The three‐component coupling reaction of phenylacetylene, amine and aldehyde was successfully catalyzed by CuOx/CeO2‐r material as a non‐homogeneous catalyst, which showed good catalytic activity. Furthermore, a series of indolizine derivatives can be obtained in higher isolated yields by replacing benzaldehyde with pyridinecarbaldehyde and catalyzing the three‐component synthesis with the same CuOx/CeO2‐r material. The synthesis mechanisms of propargylamine and indolizine were discussed. It is worth noting that the CuOx/CeO2‐r material system is provided for two three‐component reactions, and has the advantages of less catalyst dosage, short reaction time, simple post‐treatment, and a wide range of substrates. [ABSTRACT FROM AUTHOR]

For covalent attachment-supported α-diimine catalysts, on the basis of ensuring the thermal stability and activity of the catalysts, the important problem is that the active group on the catalyst can quickly react with the support, anchoring it firmly on the support, shortening the loading time, reducing the negative impact of the support on the active centers, and further improving the polymer morphology, which makes them suitable for use in industrial polymerization temperatures. Herein, we synthesized a α-diimine nickel(II) catalyst bearing four hydroxyl substituents. The hydroxyl substituents enable the catalyst to be immobilized firmly on silica support by covalent linkage in 5–10 min. Compared with the toluene solvent system, the homogeneous catalysts show high activity and thermal stability in hexane solvent at the same conditions. Compared with homogeneous catalysts, heterogeneous catalysis leads to improvements in catalyst lifetime, polymer morphology control, catalytic activity, and the molecular weight of polyethylene (up to 679 kg/mol). The silica-supported catalysts resulted in higher melting temperatures as well as lower branching densities in polyethylenes. Even at 70 °C, the polyethylene prepared by S-CatA-2 still exhibits dispersed particle morphology, and there is no phenomenon of reactor fouling, which is suitable for industrial polymerization processes. [ABSTRACT FROM AUTHOR]

The entanglement of cyclic polymers is an open issue. Cyclic poly(ε-caprolactone)s (PCLs) with a number-average molar mass (Mn) ranging from 8 to 37 kg mol−1 were synthesized using a protocol without linear precursors to avoid the influence of linear contaminants. The crystallization and melting behaviors of the synthesized unconcatenated and unknotted cyclic PCLs were investigated by DSC, POM and X-ray. The DSC and POM characterized crystallization behaviors of the cyclic PCLs showed that the half-time of crystallization and spherulite growth rate related to the molecular weights. The rheological results showed that the critical molecular weight of cyclic PCLs is 11 kg mol−1, which is about two times that of the linear PCLs. The coupling effect of ring topology and entanglement leads to the maximum crystallization rate and minimum lamellar thickness at the medium molecular weight. In situ simultaneous SAXS/WAXS probe in heating was performed on the samples after isothermal crystallization, and the results indicated that the ring topology did not change the crystal of PCL, but the evolution of nano-scale crystalline structure is different from that of the linear PCLs. The evolution of metastable crystalline structure of cyclic PCLs is discussed based on the SAXS results, and the entanglements were found to reduce the rate of structural evolution. [ABSTRACT FROM AUTHOR]

Since 2000, CO 2 emissions from emerging economies have outstripped those of developed economies. To limit global warming to under 1.5 ∘ C by 2100, over 100 emerging economies have proposed net-zero carbon targets. Yet the supportive data are lacking – no inventory of CO 2 emission outlines detailed sources by sector or distribution at the subnational level for these economies. Here, we redress the balance by establishing a dataset for an energy-related CO 2 emission inventory that covers 47 sectors and eight energy types in 40 emerging economies (10.5281/zenodo.7309360, Cui et al., 2021). Their emissions, growing rapidly by 3.0 % yr -1 , reached 7.5 Gt in 2019 and were sourced primarily in coal and oil (34.6 % and 28.1 %, respectively) and consumed by the power and transportation sectors. Meanwhile, among African countries in this group, biomass combustion was responsible for 34.7 %–96.2 % of emissions. Our dataset fills a data gap by providing a detailed, robust emission accounting baseline for emerging economies – an advance that will support emission reduction policymaking at global, national, and subnational levels. [ABSTRACT FROM AUTHOR]

Four supported α-diimine nickel(II) catalysts covalently linked to silica via hydroxyl functionality on α-diimine acenaphthequinone-backbone were prepared and used in slurry polymerizations of ethylene to produce branched polyethylenes. The catalytic activities of these still reached 106 g/molNi·h at 70 °C. The life of the supported catalyst is prolonged, as can be seen from the kinetic profile. The molecular weight of the polyethylene obtained by the 955 silica gel supported catalyst was higher than that obtained by the 2408D silica gel supported catalyst. The melting points of polyethylene obtained by the supported catalysts S-C1-a/b are all above 110 °C. Compared with the homogeneous catalyst, the branching numbers of the polyethylenes obtained by the supported catalysts S-C1-a/b is significantly lower. The polyethylenes obtained by supported catalyst S-C1-a/b at 30–50 °C are free-flowing particles, which is obviously better than the rubber-like cluster polymer obtained from homogeneous catalyst. [ABSTRACT FROM AUTHOR]

With the increase in awareness of environmental protection and the shortage of oil resources, bio-based polyurethane has attracted increasing attention due to its ecological friendliness, low cost and easy degradation. In this paper, using Eugenol (Eug) derived from plant essential oils as the raw resource, syringyl ethanol (Syol) was prepared, and three monomers were obtained by the reaction of the Eug or Syol with Hexamethylene diisocyanate (HDI)or 4,4′-methylene di (phenyl isocyanate) (MDI), respectively. Then, three novel bio-based polyurethanes, P(Eug-HDI), P(Syol-HDI) and P(Syol-MDI), were synthesized by olefin metathesis polymerization. The effects of the catalyst type, reaction solvent, reaction temperature, reaction time, molar ratio of catalyst dosage and metal salts on the Eug-HDI olefin metathesis polymerization were investigated in detail. Under the optimal conditions, the yield reached 64.7%. It is worth noting that the addition of metal Ni salts could significantly promote the polymerization, in which NiI2 could increase the yield to 86.6%. Furthermore, the thermal decomposition behaviors of these bio-based polyurethanes were explored by DSC and variable temperature infrared spectroscopy. The test results showed that P(Eug-HDI) had a reversible thermal decomposition and a certain self-healing performance. This paper provided a new method for the preparation of bio-based polyurethane. [ABSTRACT FROM AUTHOR]

Isotactic polybutene-1 (iPB-1) usually crystallizes into form II from the melt first and it then spontaneously transforms into form I with outstanding properties. The mechanism of the well-known II–I transition of iPB-1 is still an open question. In the present paper, the II–I transitions of iPB-1 samples with different molecular weights were explored via differential scanning calorimetry (DSC) and X-ray scattering (SAXS) techniques after crystallization at various temperatures. It was found that the initial and final stages of the transition process depend on the molecular weight of iPB-1. A slower II–I transition rate was observed with increasing molecular weight. The total crystallinity increases significantly in the initial stages of the transition, especially for iPB-1 with high molecular weight, after crystallization at higher temperature. The long spacing, lamellar thickness, and amorphous layer thickness of iPB-1 samples with different molecular weights increase with the isothermal crystallization temperature. The SAXS results indicated that the initial crystal transition rate of iPB-1 increases with the amorphous size after isothermal crystallization at various temperatures. The transition process was discussed and a mechanism is proposed, which is helpful for understanding the transition. [ABSTRACT FROM AUTHOR]

The use of CO2 as a CO surrogate for the carbonylation of olefin has attracted considerable attention due to its abundance, readily availability, nontoxicity, and recyclability. In this work, we describe the synthesis of methyl propionate (MPA), a key intermediate for methyl methacrylate in the commercial Lucite Alpha process, by the ruthenium-catalyzed methoxycarbonylation of ethylene with CO2 as a carbonyl source. An efficient approach to producing MPA has been developed by adding metal halide promoters and dehydrating agents. Control experiments suggest that the NHC-Ru-hydride may be the real active species formed in situ by the reaction of Ru3(CO)12 with ionic liquid (IL). NMR data demonstrate that inorganic salts favor the formation of active species, which is an important issue for their promotion effect. In terms of the strategy to overcome chemical equilibrium by the addition of dehydrating agents and IL participation in the formation of NHC-Ru-hydride active species, a tasked IL containing a siloxyl group was employed to Ru-catalyze the methoxycarbonylation of ethylene, which showed higher catalytic efficiency in comparison to IL without a siloxyl group. [ABSTRACT FROM AUTHOR]

A versatile method for the modification of three-dimensionally ordered macroporous (3DOM) highly syndiotactic polystyrene via chloromethylation at the pore walls has been demonstrated. This was followed by reaction with dimethylamine to establish a versatile approach to functionalization of such macroporous polymers. High syndiotacticity of 3DOM sPS is necessary for maintenance of the morphology of the original ordered pore structure after chloromethylation. The relative content of chloromethyl groups was shown to be 1.89 mmol/g3DOM sPS by TG-titration. The functionalized 3DOM sPS was characterized by SEM, FT-IR, and DSC to demonstrate that chloromethylation had occurred at the pore walls and that the dimethylamino moiety had replaced the chlorine atom of the chloromethyl group. DSC examination of the modified polymer indicated that the crystallinity of 3DOM sPS is little affected by functionalization. Thus the excellent properties of sPS are retained by the functionalized material. POLYM. ENG. SCI., 49:223-228, 2009. ©2008 Society of Plastics Engineers, INTRODUCTION Three-dimensionally ordered macroporous (3DOM) materials, ranging from metals, metal oxides, carbon, and silica to polymer (1-5), have attracted increasing attention due to their rich potential in a variety of [...]