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Titanium complexes bearing 2-(arylideneamino)phenolates and 2-((arylimino)methyl)phenolates were synthesized, and their catalytic activities in the polymerization of ε-caprolactone and L -lactide were studied. Among five-membered ring Ti complexes bearing 2-(arylideneamino)phenolates, FCl-Ti exhibited the highest level of catalytic activity ([CL] : [FCl-Ti] = 100 : 1, where [CL] = 2 M, and conv. = 86% at 60 °C after 9 h). For six-membered ring Ti complexes bearing 2-((arylimino)methyl)phenolates, SCl-Ti exhibited the highest level of catalytic activity ([CL] : [SCl-Ti] = 100 : 1, where [CL] = 2 M, and conv. = 88% at 60 °C after 118 h). The five-membered ring Ti complexes bearing 2-(arylideneamino)phenolates exhibited a higher level of catalytic activity (6.1–12.8 fold for the polymerization of ε-caprolactone and 6.2–23.0 fold for the polymerization of L -lactide) than the six-membered ring Ti complexes bearing 2-((arylimino)methyl)phenolates. The density functional theory (DFT) results revealed that the free energy of the first transition state FH-Ti-TS1 is 36.49 kcal mol−1 which is lower than that of SH-Ti-TS1 (46.58 kcal mol−1), which was ascribed to the fact that the Ti–Nim bond (2.742 Å) of FH-Ti-TS1 is longer than that of SH-Ti-TS1 (2.229 Å) and reduces the repulsion between ligands. [ABSTRACT FROM AUTHOR]

Most metathesis polymers based on norbornene derivatives carry a vinyl end group. Here we show that these vinyl end groups readily undergo a degenerative exchange of the terminal methylene unit in the presence of sub‐stoichiometric amounts of a propagating metathesis polymer carrying a Grubbs ruthenium complex. We show that this degenerative exchange can be exploited in synthesizing ROMP polymers in a catalytic living fashion. Chain transfer agents based on styrene, or monosubstituted conjugated 1,3 diene derivatives are used as initiating sites for the catalytic living polymerization. Suitable derivatives of these chain transfer agents not only allow the linear living growth of polymers but also the synthesis of block copolymers from macro‐initiators or star polymers from multi‐functional chain transfer agents. This reversible exchange mechanism offers a cheaper, greener, and more sustainable alternative for the synthesis of living ROMP polymers compared to the classical synthetic route. [ABSTRACT FROM AUTHOR]

Numerous zinc complexes based on N‐ and O‐donor Schiff‐base ligands have shown great promise in the ring‐opening polymerization (ROP) of lactides, which are cyclic dimers of lactic acid, to produce poly(lactic acid) (PLA). This is primarily because zinc is a borderline metal, making it non‐cytotoxic, inexpensive, abundant, biocompatible, and environmentally safe. Additionally, Schiff‐based ligands offer stability, stereoselectivity, desirable electronic and steric environments, and resistance to impurities. As a result, zinc complexes are easy to synthesize, colourless, have high reactivity and solubility in organic solvents, and are manageable under typical circumstances. Furthermore, these complexes are free to adopt a variety of coordination numbers since zinc does not have ligand field stabilization energy (LFSC). Zinc complexes possess high catalytic activity due to their distinctive properties, including high Lewis acidity, high electron transfer ability, stability concerning the reactive intermediate, and the ability to monitor polymerization by nuclear magnetic resonance (NMR) spectroscopy. Moreover, these complexes also have reasonable control over stereochemistry, number‐average molecular weight (Mn), and dispersity index (Ð). These advantages make it possible to produce colourless PLA with a high yield, high molecular weight, and narrow dispersity index in bulk and solvent‐based conditions. [ABSTRACT FROM AUTHOR]

The two‐dimensional (2D) inorganic fillers could significantly improve the properties of polyolefin, thereby satisfying a wider range of applications. Herein, in this research, high‐performance polyethylene (PE)/siloxene nanocomposites were prepared through an in‐situ polymerization with layered siloxene‐supported Ti‐based catalyst. The catalytic ethylene polymerization activity of the siloxene‐supported Ziegler‐Natta catalyst was almost twice that of the MgCl2/TiCl4 catalyst when equal weights of catalysts were used. During the in‐situ polymerization, the layered siloxene fillers exhibited uniform dispersion within the PE matrix. The incorporation of a minimal amount of siloxene filler resulted in a notable enhancement in the thermal stability and mechanical properties of PE. The breaking strength, modulus, elongation at break, and Td5% of PE/siloxene nanocomposites with only 0.71 wt% siloxene were increased by 115.7%, 45.6%, 50.6%, and 58.2°C, respectively. Therefore, this research presents a straightforward method for manufacturing PE with outstanding performance. Highlights: PE/siloxene nanocomposites were prepared through in‐situ polymerization.Siloxene is uniformly scattered in the PE matrix.The siloxene and matrix exhibit excellent interfacial adhesion.PE/siloxene nanocomposites with excellent properties were obtained. [ABSTRACT FROM AUTHOR]

Stable and inexpensive catalysts are particularly important in the catalysis industry. This study investigated cheap stable Ce2O3 and CeO2 as catalysts for the ring-opening polymerization of rac-lactide (rac-LA) and ε-caprolactone (ε-CL). Both Ce2O3 and CeO2 effectively catalyzed the polymerization of lactones. The catalytic efficiency of Ce2O3 was significantly higher than that of CeO2. The catalytic polymerization process was carried out under controlled conditions, and narrow molecular-weight distributions of polylactide and polycaprolactone were obtained. A kinetic study of the catalytic polymerization of rac-LA showed that the polymerization conformed to first-order kinetics and was controllable. [ABSTRACT FROM AUTHOR]

Ring‐opening polymerization (ROP) offers a striking solution to solve problems encountered in step‐growth condensation polymerization, including precise control over molecular weight, molecular weight distribution, and topology. This has inspired our interest in ROP of cycloalkanes with an ultimate goal to rethink polyolefins, which clearly poses a number of challenges. Practicality of ROP of cycloalkanes is actually limited by their low polymerizability and elusive mechanisms which arise from significantly varied ring size and non‐polar C−C bonds in monomers. In this work, by using Lewis acid/Brønsted base/C(sp3)‐H initiator system previously developed in our laboratory, we focus on cyclobutanes and explore the positional and electronic effects of substituents on the ring, namely electron push‐pull effect, in promoting controlled polymerization to afford densely functionalized poly(cyclobutanes), as well as catalytic degradation of obtained polymers for upcycling. More importantly, experiments and DFT calculations unveil considerable population of Lewis‐acid‐induced thermostabilized 1,4‐zwitterions, which distinguish cyclobutanes from cyclopropanes and others. All these findings would shed light on catalytic synthesis and degradation of saturated all‐carbon main‐chain polymers, as well as small molecule transformations of cyclobutanes. [ABSTRACT FROM AUTHOR]

Within bioplastics, natural poly(3‐hydroxybutyrate) (PHB) stands out as fully biocompatible and biodegradable, even in marine environments; however, its high isotacticity and crystallinity limits its mechanical properties and hence its applications. PHB can also be synthesized with different tacticities via a catalytic ring‐opening polymerization (ROP) of rac‐β‐butyrolactone (BBL), paving the way to PHB with better thermomechanical and processability properties. In this work, the catalyst family is extended based on aluminum phenoxy‐imine methyl catalyst [AlMeL2], that reveals efficient in the ROP of BBL, to the halogeno analogous complex [AlClL2]. As well, the impact on the ROP mechanism of different initiators is further explored with a particular focus in dimethylaminopyridine (DMAP), a hardly studied initiator for the ROP of BBL. A thorough mechanistic study is performed that evidences the presence of two concomitant DMAP‐mediated mechanisms, that lead to either a DMAP or a crotonate end‐capping group. Besides, in order to increase the possibilities of PHB post‐polymerization functionalization, the introduction of a side‐chain functionality is explored, establishing the copolymerization of BBL with β‐allyloxymethylene propiolactone (BPLOAll), resulting in well‐defined P(BBL‐co‐BPLOAll) copolymers. [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]

A series of bis(oxazoline) rare-earth metal dialkyl complexes [(L)Ln(CH2SiMe3)2(THF)n] (L = L1 (dimethyl-substituted bis(oxazoline) ligand), Ln = Y (1-Y), Lu (1-Lu), Sc (1-Sc), n = 1; L = L2 (phenyl-substituted bis(oxazoline) ligand), Ln = Y (2-Y), Lu (2-Lu), Sc (2-Sc), n = 2) was successfully prepared. NMR spectroscopy and X-ray diffraction indicated that all the complexes ligated with a C2 symmetric bis(oxazoline) and two trimethylsilylmethyl ligands. In the presence of borate and triisobutyl aluminium, these complexes exhibited high catalytic activity for the polymerization of isoprene, yielding the polymer with high cis-1,4-regularity (up to 99.9%) and high molecular weight. Moreover, these ternary catalytic systems also served as efficient initiators for the polymerization of polar ortho-methoxystyrene. However, atactic polymers in all the cases were isolated despite the C2 symmetric geometry of bis(oxazoline) ligands. [ABSTRACT FROM AUTHOR]

Zwitterionic catalysis is powerful in simultaneously activating electrophiles and nucleophiles in organic transformations; however, its potential in polymerizations remains untapped. Herein, a zwitterionic catalytic model for ring-opening polymerization (ROP) is introduced and a series quaternary ammonium carboxylate zwitterionic catalysts have been designed and evaluated in the ROPs of cyclic esters. Among the zwitterionic catalysts, L -carnitine, a commercially available and inexpensive natural product, showed the optimal catalytic performance. ROPs of L -lactide (L -LA), trimethylene carbonate, δ-valerolactone and ε-caprolactone were successful. PLLA was prepared with controlled molecular weight (1.4 to 21.2 kg mol−1) and narrow dispersion (Đ 1.02 to 1.21). The zwitterionic catalytic mechanism is proposed where quaternary ammonium and hydroxyl cooperatively activated the carbonyl of monomers, while the carboxylic anion activated the chain-end/initiator. NMR titrations validated the bifunctional activation mechanism. Organocatalysts of zwitterionic nature provide a new design tool for wider scope investigation of catalytic polymerizations. [ABSTRACT FROM AUTHOR]

Liquid crystal polyesters (LCPs) have attracted growing attention due to the increasing demand for military equipment and 5G communication devices. Commonly, the LCPs are polymerized by transesterification reaction catalyzed through inorganic salts, however, the effects of anionic pairs of catalysts on the LCP polymerization have not been studied carefully. Herein, five kinds of sodium salts with varied anionic pairs as catalysts to facilitate LCP polymerization are investigated for the first time. The catalytic activity is analyzed by the evolution of the liquid crystal (LC) phase during polymerization based on the thin-film polymerization technique. The temperature from 190 °C to 270 °C and the catalyst content in the range from 0 to 0.1 wt% are compared, demonstrating that temperature at 270 °C and catalyst content at 0.1 wt% are the best polymerization conditions for all sodium salts. It is found that sodium formate has the best catalytic activity for the polymerization of LCP in all experimental conditions, in comparison with sodium acetate, sodium propionate, sodium butyrate, and sodium p-hydroxybenzoate. The successful polymerization is also determined by FT-IR spectra, performing the declined intensity of vibration peak at 1370 cm−1 ascribed to the vanishment of acetoxy groups as well as the enhanced intensity of vibration peak at 1735 cm−1 ascribed to the formation of ester groups. [ABSTRACT FROM AUTHOR]

The polymerization mechanism of 2-vinylpyridine catalyzed by cationic yttrium complexes with diverse ancillary ligands, specifically [L¹Y(CH2SiMe3)(THF)]+ [L¹ = (2,6-Et2C6H3)NC(Me)CHC(Me)N(2,6-Et2C6H3)] (Y-1), [L²Y(CH2SiMe3)(THF)]+ [L² = (2,6-Cl2C6H3)NC(Me)CHC(Me)N(2,6-Cl2C6H3)] (Y-2), and [L³Y (CH2SiMe3)(THF)]+ [L³ = (2,6-C6H5)NC(Me)CHC(Me)N(2,6-iPr2C6H3)] (Y-3), was studied using density functional theory (DFT) calculations. Having achieved an agreement between theory and experiment, it is found that isotactic selectivity induced by Y-1 or Y-2 results from a combination of smaller deformation of the catalyst and stronger electronic effects. Conversely, the Y-3 complex exhibits comparable energy barriers for proceeding via either isotactic or syndiotactic pathways, aligning with the production of atactic polymers as seen experimentally. To examine the steric effects on the kinetic and thermodynamic properties, a computational model of an analogue complex [L4Y(CH2SiMe3)(THF)]+ [L4 = (2,6-Cl2C6H3)NC (Me)CHC(Me)N(iPr2C6H3)] (Y-4), featuring increased steric hindrance, was analyzed. Distortion-interaction and topographic steric map analyses further affirmed that steric hindrance significantly influences stereoselectivity. A direct relationship was identified between the energy barriers of isotactic insertion transition states and the bulkiness of ancillary ligands; greater distortion energy of the catalyst correlates with higher barriers for isotactic polymerization. These findings enhance the mechanistic comprehension of 2-vinylpyridine polymerization and are expected to contribute valuable insights for the improvement of catalytic polymerization systems of 2-vinylpyridine. [ABSTRACT FROM AUTHOR]

Bicenter (BCn) cobalt-bis(imine) catalysts were synthesized, used to polymerize methyl methacrylate (MMA), and 1-hexene. The effect of catalyst structure, bridging ligand, and polymerization reaction conditions were investigated. Synthesis of primary ligand of (2,6-dibenzhydryl-4-ethoxyphenyl)-N=(CH3)-C(CH3)=O is prepared. Following to that, the final ligands of BC1 and BC2 bicenter catalysts were prepared via reacting the primary ligand with 2,3,5,6-tetramethylbenzene-1,4-diamine and 4,4-methylenedianiline bridges, respectively. The BC1 catalyst demonstrated higher activity than the BC2 catalyst. The highest activity for the BC1 catalyst was obtained when the co-catalyst to catalyst molar ratio was [Al]/[Co]=1500:1, and the polymerization temperature was 40 °C. In comparison the BC2 catalyst demonstrated the highest activity in [Al]/[Co]=500:1 ratio, polymerization temperature of 70 °Cand showed higher thermal stability. 1HNMR analysis revealed that the highest branching density for poly(methyl methacrylates) (PMMA) produced by BC1 and BC2 catalysts was 222 and 249 branches per 1000 carbon atoms, respectively. PMMA synthesized with BC2 catalysts had the highest syndiotacticity (59%). The polymer produced with bicenter catalyst (BC1) had a relatively broad molecular weight distribution (2.9), according to GPC analysis. The synthesized catalysts demonstrated appropriate activity for the polymerization of MMA, but only moderate activity for 1-hexene monomer

Hydrogel‐based optical waveguides have attracted extensive attention in optogenetics, implantable photomedicine, and biosensors due to their excellent biocompatibility and tissue‐like modulus in compared with traditional SiO2‐based rigid optical fibers. However, the existing ion‐induced supramolecular assembly of alginate‐based hydrogel optical fibers commonly lack of long‐term stability due to poor mechanical property accompanied with swollen. In this paper, a novel catalytic surface polymerization method is developed based on a redox reaction mechanism to in situ grow robust and slippery cladding layer on a core poly(ethylene glycol) dimethacrylate (PEGDA) hydrogel fiber by using the alternative H‐bonding poly(N ‐acryloyl glycinamide) (PNAGA) hydrogels. The resultant hydrogel optical fiber with core‐cladding heterogeneous structure can achieve the desirable total reflection condition, leading to good light transmission and low light loss. The PNAGA cladding with robust H‐bonding network endows the hydrogel optical fiber with high stability and outstanding lubrication in humid environment. More importantly, the hydrogel optical fiber possesses good tissue‐like mechanical performance together with excellent biocompatibility, which shows the great advantages for biomedical applications in compared with traditional glass optical fibers. This work will broaden implantable hydrogel optical fibers in material design and structure processibility, promoting the use of hydrogel‐based optical fibers in various applications. [ABSTRACT FROM AUTHOR]

Bicenter (BCn) cobalt-bis(imine) catalysts were synthesized to be used for the polymerization of methyl methacrylate (MMA) and 1-hexene. The effect of catalyst structure, bridging ligand and polymerization reaction conditions was investigated. Synthesis of primary ligand (2,6-dibenzhydryl-4-ethoxyphenyl)-N=(CH3 )- C(CH3 )=O was also done. Following to that, the final ligands of the BC1 and BC2 bicenter catalysts were prepared via reacting the primary ligand with 2,3,5,6-tetramethylbenzene-1,4-diamine and 4,4-methylenedianiline bridges, respectively. The BC1 catalyst demonstrated higher activity than the BC2 catalyst. The highest activity for the BC1 catalyst was obtained when the co-catalyst to catalyst molar ratio was [Al]/[Co]=1500:1, and the polymerization temperature was 40°C. In comparison, the BC2 catalyst demonstrated the highest activity and higher thermal stability in the conditions of: [Al]/[Co]=500:1 ratio and 70°C polymerization temperature. The ¹H NMR analysis results revealed that the highest branching density for the poly(methyl methacrylate) (PMMA) produced by the BC1 and BC2 catalysts was 222 and 249 branches per 1000 carbon atoms, respectively. The PMMA synthesized with the BC2 catalysts had the highest syndiotacticity (59%). The polymer produced with the bicenter catalyst (BC1) showed a relatively broad molecular weight distribution (2.9), according to the GPC analysis results. The synthesized catalysts demonstrated appropriate activity for the polymerization of MMA, but only moderate activity for 1-hexene monomer. [ABSTRACT FROM AUTHOR]

Mesophase pitch is usually prepared by radical polymerization or catalytic polymerization from coal tar, petroleum, and aromatic compounds, and the catalytic synthesis of mesophase pitch from pure aromatic compounds is more controllable in the preparation of high-quality mesophase pitch. However, the corrosive and highly toxic nature of the catalyst has limited the further development of this method. In this study, mesophase pitch was synthetized using ethylene tar and naphthalene as raw materials and boron trifluoride diethyl etherate as a catalyst. The effect of the catalytic reaction on the structure and properties of the mesophase pitch was investigated. The results show that naphthalene plays an important role in the mesophase content and reaction pressure (from above 6 MPa to 2.35 MPa). Mesophase pitch with fine-flow texture can be prepared by introducing more methylene groups, naphthenic structures, and aliphatic hydrocarbons during synthesis. Carbon fibers prepared from mesophase pitch show a split structure, and the thermal conductivity is 730 W/(m·K). This work provides theoretical support for lower toxicity and causticity and for reaction-controlled technology for the synthesis of high-purity mesophase pitch. [ABSTRACT FROM AUTHOR]

The information available in daily plant operation data is not fully exploited by polymer reaction engineers: what do the catalytic olefin polymerization plants tell? In this article, a method is proposed to increase catalyst and process know‐how, based on experimentally acquired production rate results, coming from a continuous tandem reactor polymerization process. The polymer reaction engineering methodology is also discussed in detail for connecting the catalyst reaction performance to the expected activity profile and yield for batch operation, together with the residence time distribution effect for continuous operation. The potential of the proposed methodology is highlighted with a theoretical example and the effectiveness of the method is demonstrated with an applied example, accurately estimating deactivation parameter values for two catalysts based on plant information and, validated based on small‐scale polymerization experiments. [ABSTRACT FROM AUTHOR]

Seed emulsion polymerization was an effective modification method to improve not only the properties of polymers but also the compatibility between different polymers by designing special core-shell structures. In this study, poly (butadiene-styrene-vinyl pyridine) (VPR)/poly (acrylonitrile-butadiene) (NBR) core–shell nanoparticles (VPR/NBR) were prepared by seed emulsion polymerization using VPR as seed emulsion and butadiene and acrylonitrile as monomers. Subsequently, HVPR/HNBR was obtained by direct hydrogenation of the core–shell nanoparticles in latex using Wilkinson's catalyst under high temperature and H2 pressure. It is noteworthy that the unsaturated C=C double bonds in the core (VPR) and shell (NBR) of HVPR/HNBR nanoparticles were reduced simultaneously during the hydrogenation process without obvious sequence. The particle size and size distribution of the particles remained consistent before and after hydrogenation, indicating that the synthesized core-shell nanoparticles have excellent stability. This study provides a new perspective on the chemical modification of NBR and promises an environmentally friendly "green" process for the industrial hydrogenation of unsaturated elastomers. [ABSTRACT FROM AUTHOR]

Liquid crystal aromatic polyesters (LCAPs) have been used in wide applications, such as chip packaging and airship skin. The traditional polymerization of LCAP is catalyzed by inorganic salts, for example, sodium acetate. Herein, we reported three kinds of ionic liquids (ILs) as catalysts to promote LCAP polymerization for the first time. The effects of ILs on the polymerization behaviors are investigated by in situ observing the liquid crystal (LC) phase behaviors based on the thin‐film polymerization technique. The evolution of LC phase over time was detailly investigated by analyzing the emergence, fusion, and growth of LC phase. The temperature from 170 to 210°C and the catalyst concentration in range from 0 to 0.5 wt% are compared, showing that temperature at 210°C and catalyst concentration at 0.5 wt% are the best polymerization conditions for all ILs catalysts. In comparison with trimethylsulfonium iodide and piperidine acetate, 1‐ethyl‐3‐methylimidazolium acetate has the best catalytic effect for the polymerization of LCAP in all experimental conditions. The successful polymerization was confirmed by FT‐IR spectra, showing the increased intensity of vibration peak at 1735 cm−1 attributed to the generation of ester groups while the decreased intensities of vibration peaks at 1759 and 1370 cm−1. [ABSTRACT FROM AUTHOR]

The development of catalysts has significantly advanced the progress of polyolefin materials. In particular, group 4 (Ti, Zr, Hf) non-metallocene catalysts ligated with [N,N] bidentate ligand(s) have garnered increasing attention in the field of olefin polymerization due to their structurally stability and exceptional polymerization behaviors. Ligands containing nitrogen donors are diverse and at the core of many highly active catalysts. They mainly include amidine, guanidinato, diamine, and various N-heterocyclic ligands, which can be used to obtain a series of new polyolefin materials, such as ultrahigh molecular weight polyethylene (UHWMPE), olefin copolymers (ethylene/norbornene and ethylene/α-olefin) with high incorporations, and high isotactic or syndiotactic polypropylene after coordination with group 4 metals and activation by cocatalysts. Herein, we focus on the advancements and applications of this field over the past two decades, and introduce the catalyst precursors with [N,N] ligand(s), involving the effects of ligand structure, cocatalyst selection, and polymerization conditions on the catalytic activity and polymer properties. [ABSTRACT FROM AUTHOR]

In the field of polymers and organometallic chemistry, a significant gap is apparent in the area of research on well‐defined metal complexes targeted for using in catalysis leading to olefinic oligomers and polymers. Here, we report on the use in these processes the dipicolinate oxovanadium(IV) complexes, without and with auxiliary ligands, i. e. 1,10‐phenanthroline and 2,2'‐bipyridine. The investigated complexes turned out to be versatile precatalysts. After reaction with appropriate activator, they exhibited 11 times higher a catalytic activity than reference vanadium(IV) complexes with salen ligands – so far, precatalysts from a group of vanadium(IV) complexes with the highest known catalytic activity for polymerization of ethylene. In the case of the oligomerization of polar monomers (2‐chloro‐2‐propen‐1‐ol and 3‐buten‐2‐ol) the complexes described in this report have a catalytic activity (very high) similar to vanadium(IV) complexes known in the literature. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in metallocene catalysis due to the development of cyclopentadienyl (Cp) ligands by numerous researchers. Furthermore, various ligand combinations have been realized in the last 20 years for the development of post‐metallocene catalysts. Although ligands containing a Cp have been widely reported, only a few reports exist ligands based on other carbon‐only π‐electron moieties. Herein, we focused on the zirconium and hafnium with the 10π‐electron cyclooctatetraenyl (Cot) dianion as an ancillary ligand and investigated the olefin‐polymerization ability of these complexes. Thus, we performed ethylene and ethylene‐1‐octene (co)polymerization using dMAO, MMAO, and Ph3C[B(C6F5)4]/iBu3Al as cocatalysts and confirmed that completion of the polymerization reaction; the catalytic system except dMAO exhibited activities for olefin polymerization to give linear polyethylene or ethylene‐1‐octene copolymer. Furthermore, the zirconium complexes bearing trimethylsilyl‐substituted Cot ligand exhibited enhanced activities for ethylene polymerization compared with an unsubstituted CotZr catalyst. [ABSTRACT FROM AUTHOR]

The sustainable solution to the environmental problem of polymeric materials calls for efficient and well‐controlled ring‐opening polymerization catalytic systems. Inspired by the highly reactive and stereospecific bimetallic catalysts, three kinds of bimetallic Salen‐Mn catalysts supported by biaryl linking moieties are synthesized and applied to polymerization catalysis of lactide (LA) and ϵ‐caprolactone (ϵ‐CL) in this work. The polymerization is initiated in situ by the ring‐opening of epoxide compounds, in which the ionic cocatalyst could accelerate the reaction process. The Mn−Mn coordination effect contributes to the higher activity and iso‐selectivity towards LA compared to the mononuclear Salen‐Mn catalyst. The reactivity and stereoselectivity are determined by the conformation of catalysts, specifically the Mn−Mn separation and dihedral angle. Finally, the CO2‐controlled switchable polymerizations are carried out with LA and ϵ‐CL. The reversibility of the on‐off switching operation is influenced by the combination between CO2 molecules and active species. The success in binuclear Salen‐Mn catalysts not only expands the range of bimetallic catalyst analogues but also claims the promising potential of Mn‐based catalysts in practical and theoretical research. [ABSTRACT FROM AUTHOR]

Polymers that can be extracted or manufactured from renewable resources such as sugars, natural acids, or terpenes are increasingly relevant. In this context, biobased lactones are a group of monomers that can be synthesized from renewable feedstocks and combine versatility with the ability to yield high-performing materials including both thermoplastics and thermosets. In this chapter, an overview of different kinds of catalytic ring-opening polymerization (ROP) mechanisms including coordination, organocatalyzed, and enzymatic reactions is discussed. ROP of renewable lactones to yield polyesters are classified by their origin. In particular, we report on recent advances in ROP of terpene-based precursors such as limonene and pinene that lead to a variety of caprolactone derivatives which are available for polymerization. Moreover, lactones that can be converted from sugars and natural acids (e.g., fatty acids, amino acids) will be discussed. [ABSTRACT FROM AUTHOR]

Despite the Ni(II) α-diimine based ethylene polymerization catalysts were discovered almost 30 years ago, the mechanism of the ethylene polymerization over these catalysts still remains the subject of the numerous investigations. A significant progress in understanding the nature and role of the nickel compounds formed in real catalyst systems was made over the past 5–7 years. In present publication we summarized and analyzed the data on the nature and role of Ni(II) and Ni(I) species in the catalyst process. [ABSTRACT FROM AUTHOR]

The dimeric amide lanthanum complex {[ CP(O)Ph2]La[N(SiMe3)2](µ2-OP(O)Ph2)}2 (PzlMe2 is 3,5-dimethylpyrazole) bearing the N,N,O-tridentate heteroscorpionate ligand is synthesized. As found by X-ray diffraction (XRD) (CIF file CCDC no. 2212274), the complex is binuclear and its lanthanum ions are linked by two bridging monoanionic diphenyl phosphinate ligands. The synthesized lanthanum complex demonstrates a high catalytic activity in the polymerization with ring opening of rac-lactide and ε-caprolactone providing the quantitative conversion of 500 equivalents of the monomer to the polymer at room temperature within 360–720 min for rac-lactide and 10–30 min for ε-caprolactone. The formed polylactides are characterized by the atactic microstructure (Pr = 0.54–0.56) and polydispersity indices (PDI) of 1.6–2.5, whereas for polycaprolactone PDI = 2.1–2.8. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Mechanoredox chemistry that uses highly polarized piezoelectric materials as mechanoredox catalysts to promote redox reactions has emerged recently. It provides an alternative approach alongside the existing polymerization methods. Despite recent accomplishments, determining the quantitative relationship between the structure of ZnO and its catalytic performance for polymerization is still challenging. Herein, we prepared various ZnO crystals with different polar facets ratios to achieve efficient mechanically induced reversible addition‐fragmentation chain transfer polymerization (mechano‐RAFT). ZnO prepared from Zn(NO3)2 showed a high polar facet ratio of 1.66 and offered the highest catalytic activity among all ZnO samples. A near‐quantitative initiator efficiency of 99.5% and narrow molecular weight distribution were achieved for the polymerization of n‐butyl acrylate. Furthermore, the high chain‐end fidelity and chain extension capability were also evidenced by MALDI‐TOF MS and GPC analysis. This work highlighted the significant contribution of polar facets in ZnO to its catalytic activity and will guide the design of mechanoredox catalysis with superior catalytic performance in the future. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Mechanoredox chemistry that uses highly polarized piezoelectric materials as mechanoredox catalysts to promote redox reactions has emerged recently. It provides an alternative approach alongside the existing polymerization methods. Despite recent accomplishments, determining the quantitative relationship between the structure of ZnO and its catalytic performance for polymerization is still challenging. Herein, we prepared various ZnO crystals with different polar facets ratios to achieve efficient mechanically induced reversible addition‐fragmentation chain transfer polymerization (mechano‐RAFT). ZnO prepared from Zn(NO3)2 showed a high polar facet ratio of 1.66 and offered the highest catalytic activity among all ZnO samples. A near‐quantitative initiator efficiency of 99.5% and narrow molecular weight distribution were achieved for the polymerization of n‐butyl acrylate. Furthermore, the high chain‐end fidelity and chain extension capability were also evidenced by MALDI‐TOF MS and GPC analysis. This work highlighted the significant contribution of polar facets in ZnO to its catalytic activity and will guide the design of mechanoredox catalysis with superior catalytic performance in the future. [ABSTRACT FROM AUTHOR]

Industrial and disinfection wastewater typically contains high levels of organic pollutants and residue hydrogen peroxide, which have caused environmental concerns. In this work, dual‐asymmetric MnO2@polymer microreactors are synthesized via pollutant polymerization for self‐driven and controlled H2O2 decomposition. A hollow and asymmetric MnO2 nanotube is derived from MnO2 nanorods by selective acid etching and then coated by a polymeric layer from an aqueous phenolic pollutant via catalytic peroxymonosulfate (PMS)‐induced polymerization. The evolution of particle‐like polymers is controlled by solution pH, molar ratios of PMS/phenol, and reaction duration. The polymer‐covered MnO2 tubing‐structured micromotors presented a controlled motion velocity, due to the reverse torque driven by the O2 bubbles from H2O2 decomposition in the inner tunnels. In addition, the partially coated polymeric layer can regulate the exposure and population of Mn active sites to control the H2O2 decomposition rate, thus avoiding violent motions and massive heat caused by vigorous H2O2 decomposition. The microreactors can maintain the function of mobility in an ultra‐low H2O2 environment (<0.31 wt.%). This work provides a new strategy for the transformation of micropollutants to functional polymer‐based microreactors for safe and controlled hydrogen peroxide decomposition for environmental remediation. [ABSTRACT FROM AUTHOR]

Synthetic polypeptides have emerged as versatile tools in both materials science and biomedical engineering due to their tunable properties and biodegradability. While the advancements of N-carboxyanhydride (NCA) ring-opening polymerization (ROP) techniques have aimed to expedite polymerization and reduce environment sensitivity, the broader implications of such methods remain underexplored, and the integration of ROP products with other materials remains a challenge. Here, we show an approach inspired by the success of many heterogeneous catalysts, using nanoscale metal-organic frameworks (MOFs) as co-catalysts for NCA-ROP accelerated also by peptide helices in proximity. This heterogeneous approach offers multiple advantages, including fast kinetics, low environment sensitivity, catalyst recyclability, and seamless integration with hybrid materials preparation. The catalytic system not only streamlines the preparation of polypeptides and polypeptide-coated MOF complexes (MOF@polypeptide hybrids) but also preserves and enhances their homogeneity, processibility, and overall functionalities inherited from the constituting MOFs and polypeptides. Metal-based heterogeneous catalysts are widely employed in ring-opening polymerization (ROP) but up to now the exploration of metal-organic frameworks (MOF) as catalysts in ROP remains underdeveloped. Here, the authors report a MOF heterogeneous catalytic system for fast, controllable, air- and moisture-insensitive ring-opening polymerization of α-amino acid N-carboxyanhydrides, and its seamless integration with hybrid material preparation. [ABSTRACT FROM AUTHOR]

This work presents a unified polymer reaction engineering methodology for the catalytic olefin polymerization process. The proposed modelling approach offers a modelling pathway from the polymerization recipe to production rate and polymer microstructure, and finally to rheological properties. Furthermore, this work introduces for the first time the constraint of the actual reaction performance of the polymerization catalyst in the inverse rheology and microstructural deconvolution problem, limiting the solution only to the most realistic potential molecular weight distributions (MWDs) that a specific catalyst can produce. This approach can be applied for both single‐ and multi‐site catalysts, providing not a potential MWD but the unique one that the selected catalyst can offer under given polymerization conditions. Depending on the available catalyst reaction performance insight, the constraint can vary and include from the number of active sites in use to the exact kinetic parameters of each site type. The potential of the proposed methodology is highlighted within a series of indicative examples, including forward, reverse engineering and deconvolution applications. [ABSTRACT FROM AUTHOR]

A series of rare-earth metal bis(alkyl) complexes have been prepared via protonolysis reactions of tris(aminobenzyl) complexes (Ln(CH2C6H4N(Me)2-o)3) with phosphine-functionalized amidinated ligands (DippNCN(CH2)nPPh2, n = 2 (L1-H) and n = 3 (L2-H)). The X-ray diffraction of P2-Sc (DippNCN(CH2)3PPh2Sc(CH2C6H4N(Me)2-o)2) showed the un-coordination of the diphenylphosphine group due to the inherent saturation of the central metal ion. In conjunction with [Ph3C][B(C6F5)4], all the rare-earth metal complexes showed a high catalytic activity for the polymerization of 1,3-conjugated dienes (isoprene, β-myrcene and β-farnesene), affording highly 3,4-regular polymers (up to 100% 3,4-) with high molecular weight and narrow molecular weight distribution. After the abstraction of the alkyl moiety –CH2C6H4N(Me)2-o of P1-Sc by [Ph3C][B(C6F5)4], the species with the coordination of the diphenylphosphine group to the central metal probably formed, as shown in the 31P NMR spectra and DFT calculation results, and it might serve as the true active species in the 3,4-selective polymerization of 1,3-conjugated dienes. [ABSTRACT FROM AUTHOR]

A thermodynamic simulation package is developed for the catalytic polymerization of olefins in autoclave slurry, loop slurry, gas‐phase, and autoclave solution reactors. The number of components in the reactors may vary from two to six. The simulator uses the Sanchez–Lacombe theory, one of the major thermodynamic models in the polymer industry. Step‐by‐step instructions on how to specify the system, derive and solve the resulting nonlinear equations, and estimate the required thermodynamic properties are given. The software is used to describe ethylene/1‐hexene copolymerizations with hydrogen in different reactors under industrial conditions. These simulations demonstrate why thermodynamic effects must be included in olefin polymerization models. [ABSTRACT FROM AUTHOR]

Functionalized polyethylene-based nanocomposites were prepared by in situ polymerization of ethylene with modified or neat MCM-41 nanoparticles (NMCM-41). Two different synthetic approaches were investigated to improve the compatibility between the hydrophobic HDPE matrix and the hydrophilic NMCM-41: (i) incorporation of UA into the polymeric matrix by copolymerization with ethylene, promoted by the zirconocene catalyst under homogeneous conditions, in the presence of pristine NMCM-41; (ii) use of undecenoic acid (UA) as an interfacial agent to obtain decorated NMCM-41 to be used as nanofiller for the in situ ethylene polymerization, catalyzed by Cp2ZrCl2/MAO under supported conditions. The strong polar character of the carboxylic group is expected to either increase the hydrophilicity of the HDPE chains (strategy i) or interact with the NMCM-41 surface and provide an additional link to the polymeric chains via copolymerization of the vinyl group under supported conditions (strategy ii). Although metallocene catalysts have been shown to copolymerize olefins with functional monomers, the presence of oxygen-containing compounds in the reaction media strongly affects the polymerization activity as a result of the interaction of functional groups with the electrophilic active center of the catalyst. Thus, UA was pre-contacted with tri(isobutyl)aluminum (TIBA) prior to its use in the polymerization to reduce the deactivating character of the carboxylic acid groups towards the zirconocene catalyst. The influence of the UA presence on the polymerization behavior of the protection step is discussed, and the polymerization activities observed for the different approaches are compared. In addition, the thermal behavior and structural details of the resulting materials have been characterized. The impact of using neat or functionalized NMCM-41 on the final dispersion within the polymeric matrix is also analyzed, which is correlated with the mechanical performance exhibited by these HDPE_UA_NMCM-41 nanocomposites. [ABSTRACT FROM AUTHOR]

The traditional two‐component Ziegler‐Natta catalyst has low catalytic activity when initiating ring‐opening metathesis polymerization (ROMP) and is unstable and easy to generate polymerization gels. Therefore, it is necessary to add a third group of ligands with appropriate steric hindrance to improve the catalytic activity of the catalyst. The effects of ligands′ steric hindrance and other reaction conditions on the catalytic activity of tungsten hexachloride (WCl6) as catalyst and aluminum triethyl (AlEt3) as co‐catalyst were investigated. The results showed that the size of the ligands′ steric hindrance affected the catalytic activity of ROMP, and the small steric hindrance caused the polymerization rate to be too fast, which was easy to produce gels, and when the steric hindrance of the ligands was too large, its solubility was not good, which was not conducive to the normal polymerization. When stearyl alcohol was selected as the ligand, the highest catalytic activity was 3123 mol cycloolefin polymer (COP)/mol W, and the reaction speed of polymerization was also the fastest and the complete transformation only needed 30 min when the ligand/W was 25. It was found that the polymerization reaction was stable without gels and the obtained polymer molecular weight was appropriate, 17.8 kDa, under the conditions of Al/W=80, reaction temperature 60 °C, monomer concentration 10 w/v %, catalyst/monomer 5*10−4 : 1, chain transfer agent/monomer 0.005 : 1. [ABSTRACT FROM AUTHOR]

Pitch is a high-quality carbon material precursor due to the characteristics of high carbon and low ash. It is used in the preparation of supercapacitor electrode materials, which not only has a significant effect on widening the application pathway of pitch, but also on the economic efficiency of the coal chemical process.The influence of specific surface area, pore structure and surface properties of carbon materials on the performance of supercapacitors was firstly introduced, and the influence of porous carbon preparation methods（activation method, template method） and pitch pretreatment methods（component separation, pre-oxidation, catalytic polymerization, high temperature polymerization, et al.） on the structure and electrochemical properties of the prepared carbon materials were reviewed. Finally, some further insights into the development of pitch-based porous carbon are proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel N^N-bidentate chelate nickel catalyst skeleton with imidazolidin-2-imine/guanidine motif. • High activity and good thermal stability in norbornene (co)polymerization. • Good capacity of norbornene with long-chain-branched 1-alkenes. • Adjustable 1-alkene contents and T g values of cyclic olefin copolymer. • Polar functionalized cyclic olefin copolymer with reasonable incorporations The development of late transition metal catalysts bearing novel ligand platforms is a convenient pathway to obtain prospective systems with enhanced catalytic performance, however, it remains a challenge in the field of olefin (co)polymerizations. In this contribution, a new family of [N,N]-type of bidentate aldimine imidazolidin-2-imine/guanidine ligands and their nickel complexes Ni1 – Ni7 bearing a distinct six-membered chelate ring were successfully synthesized, and characterized. All of the nickel catalysts were active for norbornene polymerization with high activity of up to 7.44 × 105 g mol–1 h−1. These catalysts also copolymerized norbornene and 1-alkenes (1-dodecene and 1-octadecene) while keeping high activities to produce various norbornene-based high-molecular-weight (M n = 5.75–36.0 kg mol−1) cyclic olefin copolymers (COCs) with adjustable 1-alkene incorporations (1.44–13.30 mol%) and a wide range of T g values (102.2–271.4 °C). Moreover, with the decoration of bulky N-aryl substituents, these nickel catalysts exhibited strong tolerance towards polar monomer to promote the direct copolymerization of norbornene and methyl 10-undecenoate with high activity (up to 9.88 × 104 g mol–1 h−1), and furnished polar functionalized COCs with a high molecular weight (M n up to 72.4 kg mol−1) and reasonable polar monomer incorporations (0.19–0.45 mol%). These nickel complexes are rare examples and also promising candidates as catalysts for the efficient synthesis of various COCs. [ABSTRACT FROM AUTHOR]

Titanium, zirconium, and hafnium complexes O[Me2Si(Dip)N]2MCl2 [Dip = 2,6‐iPr2C6H3; M = Ti (1), Zr (2), Hf (3)], O[Me2Si(tBu)N]2ZrCl2 (4), and O[iPr2Si(Dip)N]2ZrCl2 (5) supported by Si‐O‐Si bridged diamido ligands were synthesized. X‐ray diffraction analysis disclosed that complex 2 displays a distorted trigonal bipyramidal geometry. Complexes 1–5, upon the activation with sMAO, exhibited diverse catalytic performance for the polymerization of ethylene and copolymerization of ethylene with norbornene or 1‐octene. For ethylene homopolymerization, both complexes 1–2 are good catalysts giving polymer with high molecular weight and narrow polydispersities. Complex 2 catalyzed copolymerization of ethylene with 1‐octene exhibiting high catalytic activity but with norbornene showing moderate activity, affording corresponding high molecular weight copolymers with relatively high comonomer incorporations of 11% and 29%, respectively. [ABSTRACT FROM AUTHOR]

Here we present a "breathing" nanogel that is fueled by CO2 gas to perform temporally programmable catalytic polymerization. The nanogel is composed of common frustrated Lewis pair polymers (FLPs). Dynamic CO2‐FLP gas‐bridging bonds endow the nanogel with a transient volume contraction, and the resulting proximal effect of bound FLPs unlocks its catalytic capacity toward CO2. Reverse gas depletion via a CO2‐participated polymerization can induce a reverse nanogel expansion, which shuts down the catalytic activity. Control of external factors (fuel level, temperature or additives) can regulate the breathing period, amplitude and lifecycle, so as to affect the catalytic polymerization. Moreover, editing the nanogel breathing procedure can sequentially evoke the copolymerization of CO2 with different epoxide monomers preloaded therein, which allows to obtain block‐tunable copolycarbonates that are unachievable by other methods. This synthetic dissipative system would be function as a prototype of gas‐driven nanosynthesizer. [ABSTRACT FROM AUTHOR]

The dinuclear aluminum salt {[iBu2(DMA)Al]2(μ-H)}+[B(C6F5)4]− (AlHAl; DMA = N,N-dimethylaniline) is the prototype of a new class of molecular cocatalysts for catalytic olefin polymerization, its modular nature offering easy avenues for tailoring the activator to specific needs. We report here, as proof of concept, a first variant (s-AlHAl) bearing p-hexadecyl-N,N-dimethylaniline (DMAC16) units, which enhances solubility in aliphatic hydrocarbons. The novel s-AlHAl was used successfully as an activator/scavenger in ethylene/1-hexene copolymerization in a high-temperature solution process. [ABSTRACT FROM AUTHOR]

Atom transfer radical polymerization (ATRP), reversible addition/fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated polymerization (NMP) are common examples of controlled polymerization processes. On the contrary, the Zn complex efficiently catalyzed random I L i -LA/ CL copolymerization; the presence of mono-lactate subunits in the copolymer clearly verified the transesterification mechanism of copolymer formation, and the Al complex was less active. An amazing variety of polymerization mechanisms enables the creation of polymers with given microstructures and comonomer sequences. [Extracted from the article]

[Display omitted] • Hollow hetero-shell structured CN@C confined graphite N in the inner shell. • The structure regulated the C N and C O and the mass transfer rate. • The reaction rate increased by 503 times. • Removal of BPAF via the polymerization pathway. Lower reaction speed and excessive oxidant inputs impede the removal of contaminants from water via the advanced oxidation processes based on peroxymonosulfate. Herein, we report a new confined catalysis paradigm via the hollow hetero-shell structured CN@C (H-CN@C), which permits effective decontamination through polymerization with faster reaction rates and lower oxidant dosage. The confined space structures regulated the C N and C O and electron density of the inner shell, which increased the electron transfer rate and mass transfer rate. As a result, C N in H-CN@C-10 reacted with peroxymonosulfate in preference to C O to generate singlet oxygen, improving the second-order reaction kinetics by 503 times. The identification of oxidation products implied that bisphenol AF could effectively remove by polymerization, which could reduce carbon dioxide emissions. These favorable properties make the nanoconfined catalytic polymerization of contaminants a remarkably promising nanocatalytic water purification technology. [ABSTRACT FROM AUTHOR]

Stimulus responsive catalysts have received increasing attention. Photoresponsive catalytic polymerization is particularly attractive because the noninvasive and versatile nature of light. Most photoresponsive ROP catalytic systems exhibit low activities, allowing ROP to be completed within several hours to 10 h. In this contribution, a series of (thio)ureas bearing dithienylcyclopentene optical molecular switch moiety are designed, synthesized, and characterized. The photoresponsive effects in (thio)urea/alkoxide mediated ROP of L‐lactide are investigated. These catalysts allow the ROP reactions of L‐lactide to be completed within a few minutes to 1 h and the resulting polyesters have narrow molecular weight distributions. The dithienylcyclopentene moiety allows photoisomerization to be completed within 1 min. The catalytic activity of the ROP catalyst can be altered by the photoisomerization of the dithienyl cyclopentene moiety by exposure to ultraviolet or visible light, respectively. [ABSTRACT FROM AUTHOR]

This paper is a review of studies on the use of the polyhedral oligomeric silsesquioxanes (POSS) of various structures in the synthesis of polyolefins and the modification of their properties, namely: (1) components of organometallic catalytic systems for the polymerization of olefins, (2) comonomers in the copolymerization with ethylene, and (3) fillers in composites based on polyolefins. In addition, studies on the use of new silicon compounds, i.e., siloxane–silsesquioxane resins, as fillers for composites based on polyolefins are presented. The authors dedicate this paper to Professor Bogdan Marciniec on the occasion of his jubilee. [ABSTRACT FROM AUTHOR]

Bio-oil emulsions were stabilized using coconut shell coke, modified amphiphilic graphene oxide, and hydrophobic nano-fumed silica as solid emulsifiers. The effects of different particles on the stability of bio-oil emulsions were discussed. Over 21 days, the average droplet size of raw bio-oil increased by 64.78%, while that of bio-oil Pickering emulsion stabilized by three particles only changed within 20%. The bio-oil Pickering emulsion stabilized by Ni/SiO2 was then used for catalytic hydrodeoxygenation. It was found that the bio-oil undergoes polymerization during catalytic hydrogenation. For raw bio-oil hydrodeoxygenation, the polymerization reaction was little affected by the temperature below 200 °C, but when the temperature raised to 250 °C, it was greatly accelerated. However, the polymerization of monocyclic aromatic compounds in the reaction process was partially inhibited under the bio-oil Pickering emulsion system. Additionally, a GC-MS analysis was performed on raw bio-oil and hydrodeoxygenated bio-oil to compare the change in GC-MS-detectable components after hydrodeoxygenation at 200 °C. The results showed that the Pickering emulsion catalytic system greatly promoted the hydrodeoxygenation of phenolic compounds in bio-oil, with most monocyclic phenolic compounds detected by GC-MS converting to near 100%. [ABSTRACT FROM AUTHOR]

Coordination polymerization of isoprene in the presence of Ziegler–Natta catalytic systems based on a mixture of neodymium and gadolinium bis(2-ethylhexyl) phosphates at the neodymium/gadolinium molar ratios of 25/75, 50/50, and 75/25 was studied. These catalytic systems exhibit high catalytic activity in isoprene polymerization, equal to that of the catalytic system based on neodymium bis(2-ethylhexyl) phosphate. The influence of the Nd/Gd ratio on the molecular-mass characteristics and microstructure of the polymers obtained was examined. The kinetic parameters of the isoprene polymerization using catalytic systems based on a mixture of neodymium and gadolinium salts were determined. The possibility of using such systems in the synthesis of stereoregular cis-1,4-polyisoprene with the optimum level of molecular masses was demonstrated. [ABSTRACT FROM AUTHOR]

To date, nickel(II) complexes have not been practically investigated as catalysts in ring-opening polymerization (ROP) of lactide to produce biodegradable poly(lactic acid), which is in demand in biomedicine and industry. In this study, carboxylate complexes of nickel(II) containing various N-donor ligands with different nuclearity, metal core rigidity and nature of carboxylate ligands were synthesized and studied by infrared spectroscopy, X-ray diffraction, elemental and thermogravimetric analyses. The obtained complexes were examined in the ROP of the rac-lactide in bulk and in toluene solution with and without the addition of a benzyl alcohol initiator. In the series of complexes studied, the complex [Ni(DBED)2(O2CC(CH3)3)2]·(CH3)3CCO2H (DBED is N,N′-dibenzylethylenediamine) was a syndioselective catalyst and showed the highest catalytic ability in the polymerization without the addition of benzyl alcohol. For this complex, according to 1D DOSY 1H NMR spectroscopy and mass spectrometry with electrospray ionization, polymerization is initiated by a free secondary amine, DBED, leaving the metal's inner coordination sphere. Based on the experimental data obtained, a comprehensive density functional theory (DFT) study of the ROP pathways including the initiation and first chain growth cycle steps with a detailed description of the intermediates and evaluation of the energy barriers of the steps was carried out. It was shown that one of the key roles in the reaction process is played by carboxylate ligands, which act as proton carriers from the initiator molecule and have a significant influence on the reactivity of the catalytic metal complexes. [ABSTRACT FROM AUTHOR]

Poly(acrylonitrile- co -butadiene) nanoparticles were synthesized by semibatch microemulsion polymerization. The microstructure of the polymers was characterized by 1H NMR and FT-IR. The particle size of the nitrile butadiene rubber (NBR) latex could be well controlled by reaction temperature, surfactant concentration, and feeding time of monomer. The minimum particle size of 34.2 nm could be achieved by using the surfactant/monomer mass fraction of 7.9 wt%. The latex can be directly catalyzed for hydrogenation using Wilkinson's catalyst (RhCl(PPh 3) 3) and second generation Grubbs catalyst (Grubbs II), respectively. The hydrogenated products (HNBR) with a degree of hydrogenation above 95 mol% were obtained. The fast rate of hydrogenation demonstrates the unique advantages of small particle size. [Display omitted] • NBR particles were synthesized by semibatch microemulsion polymerization. • The smallest particle size with 34 nm can be obtained. • Catalytic hydrogenation of diene-based polymers in aqueous solutions was realized. • Smaller NBR particles have faster mass transfer efficiency and hydrogenation rates. [ABSTRACT FROM AUTHOR]

[Display omitted] • A method for enhancing Ti catalyzed ethylene chain transfer polymerization efficiency. • Using AlEt 3 and ZnEt 2 shows cooperative effects vs. using them separately. • Chain growth and transfer are simultaneously enhanced in ethylene polymerization. Developing olefin polymerization catalytic systems for both high activity and high chain transfer efficiency by using coordinative chain transfer polymerization (CCTP) is critical for the controlled synthesis of various novel high-value polyolefin materials. While the limited choice of chain transfer agents (CTAs) makes it a challenge to achieve highly efficient CCTP as well as chain propagation due to their competition during the polymerization. Here we report using the combination of R 3 Al and R 2 Zn in equal amount for tetradentate amine-bis(phenolate) Ti complex and tridentate ketoiminate Ti complex catalyzed ethylene polymerization and observed significantly enhanced CCTP catalytic performance in terms of activity, chains/cat, fill ratio, and k ct / k p vs. using R 3 Al as CTA. The role of R 3 Al and R 2 Zn during ethylene polymerization were probed by preliminary control experiments studies and a possible mechanistic scenario was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Establish the relationship between the self-strengthening polymer and the activation mechanism. • Evaluate the impact of the self-strengthening response on the material properties. • Provide promising solutions and potential research directions. Force-responsive, self-strengthening polymers refer to those that, under the stimulus of mechanical forces, have mechanophore groups capable of reacting with additives or themselves for strengthening. Due to the effective mitigation of fracture defects and the resultant extension of the practical lifespan, these force-responsive, self-strengthening materials have attracted extensive research interests. This paper classifies these self-strengthening polymers into categories by their activation mechanisms, namely in situ crosslinking, free radical polymerization and catalytic polymerization. Detailed discussions on the preparation methods, properties and activation mechanisms are provided, along with a prospective outlook on the development of force-responsive, self-strengthening polymeric materials. [ABSTRACT FROM AUTHOR]