ABSTRACT Direct alcohol fuel cells (DAFCs) running on liquid alcohols offer higher energy densities and much easier and safer operation than hydrogen. However, DAFCs face significant challenges in using high‐loading Pt‐based catalysts at both the anode and cathode, where the alcohol oxidation reaction and oxygen reduction reaction still suffer slow kinetics, as well as alcohol crossover causing cathode poisoning. Here, we report a breakthrough in alternative solar‐driven redox‐catalyzed direct alcohol fuel cells (SR‐DAFCs), that avoid using Pt catalysts and can operate with a range of alcohols. They mechanistically alter the conventional solid/liquid/gas heterogeneous electrocatalytic reaction pathways, into liquid homogeneous organic redox couples that mediated alcohol photocatalytic oxidation reaction at the anode, and oxygen electrochemical reduction reaction at cathode. The SR‐DAFCs exhibited record high‐power density up to 319.2 mW cm −2 with various alcohols feed, that is 3 times higher than traditional DAFC, demonstrating great potential of using unrefined alcohols as an economical fuel source for wider applications.

The synthesis of ultra-high-molecular-weight (UHMW) ethylene-propylene (EP) polar elastomers with high functional degree represents a great challenge. The modification of UHMW EP-5-ethylidene-2-norbornene (ENB) terpolymers (EPDM) with a high content of ENB structural units provides a viable way. The synthesis of UHMW EPDM with a high content of ENB structural units is critical for the preparation of UHMW polar EP elastomers with high functional degree. Herein, the copolymerization of ethylene with propylene and the terpolymerization of ethylene and propylene with ENB were investigated by using N-heterocyclic carbene vanadium complex NHCVOCl3 (PhCH2NCH=CHN(2,4,6-Me3C6H2R)C:VOCl3). The UHMW EPDM (Mw = 1059-1586 kgmol-1) were successfully prepared with high catalytic activity of <= 2.65 x 105 g polymermol-1 of Vh-1. The content of ENB structural units in resulting EPDMs can be increased to 12.5 mol% (35.4 wt%) by increasing the ENB concentration in monomer feed. The epoxidation of UHMW EPDM with m-chloroperbenzoic acid in tetrahydrofuran results in an efficient conversion of C=C double bonds in the ENB structural units into epoxy groups. The functionalized EP elastomers containing epoxy groups of <= 11.2 mol% have been successfully synthesized. The epoxy groups in the functionalized EP elastomers can be successfully and quantitatively converted into carbonyl groups, affording functionalized EP elastomers with a high content of norcamphor structural units of <= 11.2 mol%. The UHMW EPDM with a high content of polar epoxy or carbonyl groups can behave with good compatibility with inorganic fillers, which is a benefit for the preparation of high-performance composites of UHMW EPDM with inorganic fillers. Ultra-high molecular weight ethylene-propylene-diene rubber is produced via the copolymerization of ethylene with propylene and the terpolymerization of ethylene and propylene with 5-ethylidene-2-norbornene using a vanadium catalyst.

Marangoni self-propulsion refers to motion of liquid or solid driven by a surface tension gradient, and has applications in soft robots/devices, cargo delivery, self-assembly etc. However, two problems remain to be addressed for motion control (e.g., ON–OFF) with conventional surfactants as Marangoni fuel: (1) limited motion lifetime due to saturated interfacial adsorption of surfactants; (2) in- situ motion stop is difficult once Marangoni flows are triggered. Instead of covalent surfactants, supra-amphiphiles with hydrophilic and hydrophobic parts linked noncovalently, hold promise to solve these problems owing to its dynamic and reversible surface activity responsively. Here, we propose a new concept of ‘supra-amphiphile fuel and switch’ based on the facile synthesis of disodium-4-azobenzene-amino-1,3-benzenedisulfonate (DABS) linked by a Schiff base, which has amphiphilicity for self-propulsion, hydrolyzes timely to avoid saturated adsorption, and provides pH-responsive control over ON-OFF motion. The self-propulsion lifetime is extended by 50-fold with DABS and motion control is achieved. The mechanism is revealed with coupled interface chemistry involving two competitive processes of interfacial adsorption and hydrolysis of DABS based on both experiments and simulation. The concept of ‘supra-amphiphile fuel and switch’ provides an active solution to prolong and control Marangoni self-propulsive devices for the advance of intelligent material systems.

Ethylene/propylene/5-ethylidene-2-norbornene terpolymers with high ENB incorporation and ultra-high molecular weight were synthesized by using imidazolidin-2-iminato vanadium complexes.

Open-tubular immobilized enzyme microreactors (OT-IMERs) are some of the most widely used enzyme reaction devices due to the advantages of simple preparation and fast sample processing. However, the traditional approaches for OT-IMERs preparation had some defects such as limited enzyme loading amount, susceptibility to complex sample interference, and less stability. Here, we report a strategy for the preparation of highly active and stable OT-IMERs, in which the single-stranded DNA-enzyme composites were immobilized in capillaries and then encapsulated in situ in the capillaries via zeolitic imidazolate frameworks (ZIF-L). The phosphate groups of the DNA adjusted the surface potential of the enzyme to negative values, which could attract cations, such as Zn2+, to promote the formation of ZIF-L for enzyme encapsulation. Using chymotrypsin (ChT) as a model enzyme, the prepared ChT@ZIF-L-IMER has higher activity and better affinity than the free enzyme and ChT-IMER. Moreover, the thermal stability, pH stability, and organic solvent stability of ChT@ZIF-L-IMER were much higher than those of free enzyme and ChT-IMER. Furthermore, the activity of ChT@ZIF-L-IMER was much higher than that of ChT-IMER after ten consecutive reactions. To demonstrate the versatility of this preparation method, we replaced ChT with glucose oxidase (GOx). The stability of GOx@ZIF-L-IMER was also experimentally demonstrated to be superior to that of GOx and GOx-IMER. Finally, ChT@ZIF-L-IMER was used for proteolytic digestion analysis. The results showed that ChT@ZIF-L-IMER had a short digestion time and high digestive efficiency compared with the free enzyme. The present study broadened the synthesis method of OT-IMERs, effectively integrating the advantages of metal-organic frameworks and IMER, and the prepared OT-IMERs significantly improved enzyme stability. All of the results indicated that the IMER prepared by this method had a broad application prospect in capillary electrophoresis-based high-performance enzyme analysis.

The highly efficient method has been developed for the synthesis of NHC-VOCl3 containing symmetrical or unsymmetrical N-heterocyclic carbene (NHC) ligands by the transmetallation reaction of NHG·AgCl with VOCl3. The total isolated yield of VOCl3[1,3-(2,4,6-Me3C6H2)2(NCH=)2C:] (V4′) reached 86

A series of polyisobutylene-based thermoplastic elastomers (PIB-TPE) with different polybutyl carbamate hard segments could be synthesized via reaction of hydroxyl-terminated PIB telechelics (HO-PIB-OH) with bis(4-isocyanatocyclohexyl)methane (HMDI) and then 1,4-butanediol (BDO). The influence of HMDI/PIB molar ratio on the aggregation structure, elastic recovery, self-healing property, hydrophilcity/hydrophobicity on the elastomer surface, dynamic mechanical and tensile properties of PIB-TPE were systematically investigated. The flexible PIB segments with fully saturated structure in PIB-TPE serve as soft segments. The physically crosslinked domains ((3.6 +/- 0.5) nm) were generated due to the microphase separation between soft segments and hard segments and the crystallization from the ordered and disordered hydrogen bonds in polybutyl carbamate hard segments. The three-dimensional supramolecular network in PIB-TPE is formed at room temperature and dissociated to transform into viscous state due to melting of crystallization and dissociation of hydrogen bonds at high temperature and then gradually returned to the three-dimensional supramolecular network with decreasing temperature. The temperatures of melting of crystallization and dissociation of hydrogen bond depend on the length of hard segments in PIB-TPE. When the molar ratio of HMDI to PIB is less than 19, the temperature of melting peak of crystallization in hard segments is higher than 119 degrees C. Some of the disordered hydrogen bonds in PIB-TPE could change into the ordered hydrogen bonds with storage time, leading to a great improvement in tensile strength and elongation at break of PIB-TPE materials. The PIB-TPE materials behave good elastic recovery and self-healing properties. The hydrophilcity/hydrophobicity on the PIB-TPE film surface could be adjusted by the molar ratio of HMDI to PIB or self-assembly induced by n-hexane vapor. The water contact angle (WCA) on surfaces of elastomer film decreased from 98.7 degrees to 77.8 degrees with an increase in the molar ratio of HMDI to PIB from 6 to 21, meaning a change from hydrophobicity to hydrophilicity. Moreover, the fully saturated PIB soft segments endow PIB-TPE elastomer with good damping performance with relatively broad damping temperature range of -55 similar to 25 degrees C and the maximum tan delta of 1.05. The above multi-block PIB-based thermoplastic elastomers would have the potential applications as biomedical, damping and self-healing functional materials.

Main observation and conclusionStyrene polymerization catalyzed by the half‐titanocenes CpTiCl2[1,3‐R2(CH2N)2C=N] (6b: R= 2,6‐Me2C6H3, T4: R = 2,4,6‐Me3C6H2; T5: R = 2,6‐iPr2C6H3) was carried out in the presence of methylaluminoxane (MAO). Compared to the styrene conversion (31%) and syndiospecific index (45%) using reported 6b as precatalyst, T5 bearing ligand with isopropyl substitutes on the N‐aryl‐rings exhibits much higher styrene conversion (61%) and syndiospecific index (99%), indicating that the catalytic behavior could be improved obviously by the introduction of electronic donating and steric bulky substituents. One N atom in imidazolin‐2‐iminato ligand was replaced by O atom, affording half‐titanocenes CpTiCl2[3‐C6H5(CH2N)(CH2O)C=N (T1) and CpTiCl2[2,6‐Me2(C6H3O)(NiPr2)C=N] (T2). Compared to 6b, both higher styrene conversion and syndiospecific index are afforded by using half‐titanocene T1 containing 2‐imino‐3‐phenyloxazolidine ligand. All the results illustrate that both the chemical structure and the nature of substituents of the ligand have obvious influence on the styrene conversion and syndiospecific index in the polymerization of styrene. All the resulting syndiotactic polystyrenes (sPSs) are highly syndiospecific (rrr > 99%). Correspondingly, the sPS prepared using T5/MAO catalytic system exhibits high melting point and narrow molecular weight distribution. The results might show new light on designing more efficient half‐titanocenes for styrene polymerization with both high styrene conversion and high syndiospecific selectivity.

Ethylene-propylene rubber, linear low-density polyethylene and polyolefin elastomer, which are prepared by copolymerization of ethylene with alpha-olefins, have an important market share of the industry due to their excellent properties. Catalyst plays important role in the copolymerization of ethylene with alpha-olefins. Many vanadium complexes in the oxidation states of +3, +4 and +5 have been developed as precatalyst for the copolymerization. The progress of vanadium complex catalysts and their use in copolymerization of ethylene with alpha-olefins were reviewed. The effects of chelated ligands on the catalytic activity of catalysts, composition, molecular weight, molecular weight distribution and sequence of the resulting copolymers were discussed. Vanadium(III) complexes are widely used since vanadium(III) species are usually considered as active species in olefin coordination polymerization. Vanadium(III) complexes bearing monodentate N-heterocyclic carbene (NHC) ligand or bidentate beta-diketonate ligands have been used as precatalyst in copolymerization of ethylene with propylene, affording ethylene-propylene copolymers with high propylene content. Ethylene-propylene copolymers with ultra-high molecular weight were prepared by using vanadium(III) complexes containing NHC ligand. Vanadium(III) complexes bearing chelated bidentate (NN)-N-boolean AND or (NO)-O-boolean AND, etc. ligands show high catalytic activity up to 8820 kg mol(-1) h(-1) toward copolymerization of ethylene with 1-hexene. The introduction of bulky substitutes on the ligand results in an increase in the reactive ratio of ethylene and a decrease in the reactive ratio of 1-hexene, and thus a change in the sequence of monomer in the resulting copolymer. Vanadium(III) complexes containing tridentate and tetradentate ligands display relatively lower catalytic activity than their analogues containing similar bidentate ligand. Most vanadium(IV) complexes display lower catalytic activity than vanadium(III) complexes bearing similar ligands. Ethylene-propylene copolymer with high propylene content could be prepared by copolymerization of ethylene and propylene catalyzed by vanadium(IV) complexes containing monodentate amide ligands. Vanadium(V) complexes bearing chelating aryloxides have been shown to be highly active (up to 144400 kg mol(-1) h(-1)) in copolymerization of ethylene with propylene, affording ethylene-propylene copolymers with low propylene content (less than 15%(mol)). Ethylene-propylene copolymers with high propylene content (more than 30%(mol)) could be prepared by vanadium complexes containing monodentate or bedentate ligands. It is interesting to note that quasi-living copolymerization of ethylene with propylene was realized by using vanadium(V) complexes containing NHC ligand and ethylene-propylene copolymers with ultrahigh molecular weight and narrow molecular weight distribution were obtained. In conclusion, the vanadium complex catalysts have displayed good catalytic behavior towards the copolymerization of ethylene with alpha-olefins. The vanadium complexes discussed here may be an inspiration for future work in the development of vanadium complex catalyst with high catalytic activity and high comonomer incorporation for copolymerization of ethylene with alpha-olefins.

Highly efficient terpolymerization of ethylene, propylene and 5-ethylidene-2-norbornene using a half-titanocene containing iminoimidazolidine with methylaluminoxane/Al(iBu) 3 /2,6-ditertbutyl-4-methyl-phenol was achieved.

The cross-linked imidazolium functionalized anion-exchange membranes is in-situ prepared via reaction of chloromethylated poly(styrene-b-isobutylene-b-styrene) with 1,1?-(1,6-hexanediyl)bisimidazole and N-methylimidazole. The composite membranes of cross-linked imidazolium poly(styrene-b-isobutylene-b-styrene) with a small amount of modified graphene oxide grafted with octadecyl and propyl phenyl imidazolium could be further prepared. These membranes exhibit significantly high chemical stability and ionic conductivity (?), marked by low methanol permeability, together with improved dynamic mechanical properties. The ionic conductivity of cross-linked imidazolium poly(styrene-b-isobutylene-b-styrene) reaches 2.09 x 10-2 S cm- 1 at 80 ?C by introduction of 0.5 wt% loading of modified graphene oxide. This membrane also behaves an excellent chemical stability and ? can remain ca. 82% of the original value after immerged in strong alkaline medium (2 M NaOH) at 60 ?C for 500 h, which is almost the same as that (ca. 82%) of commercial Nafion 115 in acid medium (2 M H2SO4) at 60 ?C for 500 h. The cross-linked imidazolium poly(styrene-b-isobutylene-b-styrene) is characterized as a promising anion exchange membrane materials in fuel cell for its high ionic conductivity, chemical stability and low methanol permeability.

Neodymium complexes containing N-heterocyclic carbene (NHC) ligands, NdCl3[1,3-R2(NCH=)2C:]·THFx(Nd1: R = 2,6-iPr2C6H3, x = 0; Nd2: R = 2,6-Et2C6H3, x = 1; Nd3: R = 2,4,6-Me3C6H2, x = 1) were synthesized and employed as precatalysts for the coordination polymerization of conjugated dienes (butadiene and isoprene). In combination with triisobutylaluminium (TIBA), Nd1 promoted butadiene polymerization to produce extremely high cis-1,4 (up to 99.0%) polybutadienes with high molecular weight (Mw = 250–780 kg·mol−1). The Nd1/TIBA catalytic system also exhibited both high catalytic activity and cis-1,4 selectivity (up to 97.8%) for isoprene polymerization. The catalytic activity, molecular weight and molecular weight distribution of resulting polydienes were directly influenced by Al/Nd molar ratio, aging method, and polymerization temperature. Very interestingly, the high cis-1,4 selectivity of the catalyst towards butadiene and isoprene kept almost unchanged under different reaction conditions. The cis-1,4 polyisoprenes with high molecular weight (Mw = 210–530 kg·mol−1) and narrow molecular weight distribution (Mw/Mn = 1.9–2.7) as well as high cis-1,4 selectivity (~97%) could be synthesized by using the aged Nd1/TIBA catalytic system in the presence of isoprene (100 equivalent to Nd) at low Al/Nd molar ratios of 6–10. Polyisoprenes with low molecular weights (Mw = 12–76 kg·mol−1) and narrow molecular weight distributions (Mw/Mn = 1.7–2.6) were obtained by using Nd2 and Nd3 as precatalysts, indicating that the molecular weight of resulting polyisoprenes can be adjusted by changing the substitutes of ligand in Nd complex.

Vanadium catalysts, among the most important ones, display unique characteristics in olefin polymerization, namely in the preparation of amorphous polymers in ethylene/propylene/non-conjugated diene copolymerization, syndiotactic polypropylene in propylene polymerization and polyethylene with high-molecular weight. In this chapter, the efficient vanadium catalysts with various ligands for olefin oligomerization, polymerization and copolymerization will be introduced in detail.

Vanadium catalysts, among the most important ones, display unique characteristics in olefin polymerization, namely in the preparation of amorphous polymers in ethylene/propylene/non-conjugated diene copolymerization, syndiotactic polypropylene in propylene polymerization and polyethylene with high-molecular weight. In this chapter, the efficient vanadium catalysts with various ligands for olefin oligomerization, polymerization and copolymerization will be introduced in detail.

Inspired by the intriguing capability of beetles to quickly slide on water, scientists have long translated this surface-tension-gradient–dominated Marangoni motion into various applications, for example, self-propulsion. However, this classical spontaneous motion is limited by a short lifetime due to the loss of the surface tension gradient. Indeed, the propellant of amphiphilic surfactants can rapidly reach an adsorption equilibrium and an excessive aggregation state at the air/liquid interface. Here, we demonstrate a supramolecular host–guest chemistry strategy that allows the breaking of the physical limit of the adsorption equilibrium and the simultaneous removal of surfactant molecules from the interface. By balancing the competitive kinetics between the two processes, we have prolonged the lifetime of the motion 40-fold. Our work presents an important advance in the query of long-lived self-propulsion transport through flexible interference at the molecular level and holds promise in electricity generation applications .

ABSTRACTThe quasi‐living copolymerization of ethylene with propylene was achieved by using N‐heterocyclic carbene (NHC) ligated vanadium complex (V3, VOCl3[1,3‐(2,6‐iPr2C6H3)2(NCH)2C:]) due to the stabilization of active center by the introduction of bulky and electron rich NHC ligand with bulky isopropyl substituents at the ortho positions of the phenyl rings. The weight‐average molecular weight (Mw) of the resulting copolymer increases linearly with its weight in 20 min. The ultra‐high‐molecular‐weight (UHMW) ethylene‐propylene copolymer (Mw = 1612 kg mol−1) can be synthesized with V3/Et3Al2Cl3 catalytic system. The novel complex V4′ (VCl3[1,3‐(2,4,6‐Me3C6H2)2(NCH)2C:]·2THF) was constructed by the introduction of two coordinated tetrahydrofuran molecules and decrease in steric hindrance at the ortho positions of phenyl rings. The UHMW ethylene‐propylene copolymer (Mw = 1167 kg mol−1) can also be synthesized by using V4′/Et3Al2Cl3 catalytic system. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 553–561

A highly effective alcoholysis of ethylene-vinyl acetate (EVA) copolymers has been achieved to prepare ethylene-vinyl alcohol (EVOH) copolymers with various ethylene contents (30.2-49.5 mol %) having ca. 100% of alcoholysis degree even at a very low catalyst dosage. The kinetics show that the alcoholysis rate strongly depends on the composition and sequence of the EVA copolymer. The alcoholysis rate decreases with increasing E content and decreases in the order of VAcVAcVAc > VAcVAcE > EVAcE triad sequence. The formation of densely packed regions in EVOH from VVV, EVE, and EEE triad sequences along macromolecular chains via hydrogen bonds and crystallization makes a great contribution to inhibit oxygen transmission and thus to improve the barrier property. To the best of our knowledge, this is the first example to reveal the effect of sequence on alcoholysis of EVA and the oxygen barrier property of EVOH, which is profitable for macromolecular engineering of high performance EVOH copolymers.

Polyolefin materials, such as polyethylene, polypropylene, polyisobutene, ethylene-propylene rubber and isobutene rubber, play important roles in the industry and our daily life. Polyolefin materials with high performance, various microstructure, sequence distribution and topological structure could be prepared by controlled polymerization of olefin. We summarized the recent work on ethylene/propylene coordination copolymerization and isobutene cationic polymerization to prepare ethylene-propylene rubber, isobutene rubber and polyisobutene. The design and synthesis of Ziegler-Natta vanadium catalysts, half-titanocene catalysts and single-site vanadium catalyst and their application for ethylene/propylene copolymerization were introduced. The novel initiating system for the controlled/living cationic polymerizations, transformation of polymerization character, cationic polymerization in aqueous medium with high efficiency, cationic polymerization in rotating packed bed reactor were developed. The macromolecular engineering based on the controlled polymerization of olefin was also introduced.

Macroscopic supramolecular assembly (MSA) is a rising concept in supramolecular science, in which building blocks with sizes exceeding 10 μm self-assemble into larger structures. MSA faces the challenge of developing appropriate self-propulsion strategies to improve the motility of the macroscopic building blocks. Although the Marangoni effect is an ideal driving force with random motion paths, excessive aggregation of the surfactant and fast decay of motion remain challenging problems. Hence, a molecular interference strategy to drive the self-assembly over longer times by finely controlling the interfacial adsorption of surfactants using dynamic equilibria is proposed. Surfactant depletion through molecular recognition in the solution to oppose fast interfacial aggregation efficiently facilitates macroscopic motion and assembly. The resulting motility lifetime is extended remarkably from 120 s to 2200 s; with the improved kinetic energy, the assembly probability increases from 20 % to 100 %.