Microstructure characterization of short-chain branching polyethylene with differential scanning calorimetry and successive selfnucleation/annealing thermal fractionation

A series of the copolymers of ethylene with 1-hexene(M1–M9) synthesized by metallocene catalyst Et[Ind]2ZrCl2/MAO was studied by differential scanning calorimetry and successive self-nucleation and annealing(SSA) thermal fractionation. The distribution of methylene sequence length(MSL) in the different copolymers was determined using the SSA method. The comonomer contents of samples M4 and M5 are 2.04 mol% and 2.78 mol%, respectively. Both M4 and M5 have low comonomer content and their MSL distribution profiles exhibit a monotonous increase trend with their MSL. The longest MSL of M5 is 167, and its corresponding molar percent is 43.95%, which is higher than that of M4. Moreover, the melting temperature(Tm) of M5 is also higher than that of M4. The comonomer contents of samples M7, M8, and M9 are 8.73 mol%, 14.18 mol% and 15.05 mol%, respectively. M7, M8, and M9 have high comonomer contents, and their MSL distribution profiles display unimodality. M7 has a lower peak value of 33 and a narrow MSL distribution, resulting in a Tm lower than that of M8 and M9. The MSL and its distribution are also key points that influence the melting behavior of copolymers. Sometimes, MSL and its distribution of copolymers have a greater impact on it than the total comonomer contents, which is different from traditional views.     

Facile synthesis of 4-vinylpyridine-based hydrogels via laser-ignited frontal polymerization and their performance on ion removal

We report herein the fabrication of poly(AAM-co-4VP) hydrogels (AAM?=?acrylamide, 4VP?=?4-vinylpyridine) by using laser-ignited frontal polymerization (LIFP) in an easy and rapid way. The appropriate amounts of AAM, 4VP, γ-methacryloxypropyltrimethoxysilane-modified nanosilica, and couple redox initiator of ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine were mixed together in the presence of dimethylsulfoxide as solvent. LIFP was initiated by heating the upper side of the mixture with the laser. Once initiated, no further energy or treatment was required for the following polymerization to occur. A variety of features for the preparation of hydrogels, such as the initiator concentration and the ratio of different monomers, were thoroughly investigated. The morphology and swelling behavior of hydrogels were investigated. For comparison, the hydrogels prepared via traditional thermal frontal polymerization were also presented and discussed. Furthermore, the hydrogels possess absorption capacity towards copper ions, which can be applied to remove heavy metals.     

Ring-opening polymerisation of ɛ-caprolactone catalysed by Brønsted acids

Two new Brønsted acids [2,2′-ethylidene-bis (4,6-di-tert-butylphenol)] phosphoric acid (EDBPPOOH) and (3,3′,5,5′-tetra-tert-butylbiphenyl-2,2′-diol) phosphoric acid (TBPO-POOH) were synthesised and fully characterised by ¹H NMR and ¹³C NMR spectra and mass spectra. The ringopening polymerisation (ROP) of ?-caprolactone (?-CL) catalysed by the two Brønsted acids proceeded at 110°C without a solvent or at ambient temperature in toluene. Experimental results indicated that the two Brønsted acids were efficient catalysts for the ROP of ?-CL with moderate number-average molar mass (Mn) and narrow polydispersity indices (PDI). The catalytic activity of TBPO-POOH is higher than EDBP-POOH in the ROP of ?-CL. After benzyl alcohol was added, it was able to accelerate the polymerisation process. The polymerisation can also occur with the addition of water with a monomer/catalyst/initiator mole ratio of 100: 1: 1. The living polymerisation was ascertained by the linear relationships of the Mn vs. monomer conversion, then it was further confirmed by a second-feed experiment of a double monomer producing double Mn. A kinetic study of the relationships between monomer concentration and time revealed a first-order dependence on monomer concentration in the polymerisation. End-group analysis of ¹H NMR spectra and electrospray-ionisation mass spectra suggests that the two Brønsted acids are capable of catalysing and initiating the ROP of ?-CL.     

聚合物锂离子电池界面相容性的研究进展

聚合物锂离子电池作为储能装置在电子产品中具有广泛的应用前景。电极/聚合物电解质(E/P)界面相容性是影响聚合物锂离子电池电导率、安全性、机械性能的重要影响因素之一。研究E/P界面的电化学反应及形成机理,是解决相容性问题的关键。本文综述了近年来有关聚合物锂离子电池E/P界面相容性及相关研究技术的进展,并对聚合物锂离子电池界面相容性的相关研究进行了展望。     

Synthesis and structure of novel 6-(pyrazol-1-yl)-4-methyl-1H-pyrazolo[3,4-b]pyridin-3-ol derivatives

New 6-(pyrazol-1-yl)pyrazolo[3,4-b]pyridin-3-ol compounds were synthesized by cyclization reaction from 2,6-dichloro-4-methylnicotinonitrile. Their derivatives exist as the 3-hydroxy tautomer. The structure of the compound 1a of one of the resulting compounds was studied in detail by X-ray diffraction.     

Catalytic oxidation of NO over Mn–Co–Ce–Ox catalysts: effect of reaction conditions

Manganese–cobalt–cerium oxide (Mn–Co–Ce–Ox) catalysts were synthesized by the co-precipitation method and tested for activity in low-temperature catalytic oxidation of NO in the presence of excess O₂. With the best Mn–Co–Ce mixed-oxide catalyst, approximately 80 % NO conversion was achieved at 150 °C and a space velocity of 35,000 h^?1. The effect of reaction conditions (reaction temperature, volume fractions of NO and O₂, gas hourly space velocity (GHSV), and catalyst stability) was investigated. The optimum reaction temperature was 150 °C. Increasing the O₂ content above 3 % results in almost no improvement of NO oxidation. This catalyst enables highly effective removal of NO within a wide range of GHSV. Furthermore, the stability of the Me–Co–Ce–Ox catalyst was excellent; no noticeable decrease of NO conversion was observed in 40 h.     

A Hydrogen-Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

Developing highly efficient and low-cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble-metal co-catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so-called L-NiCo nanosheets with a nonstoichiometric composition and O²⁻/Co³⁺ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O²⁻ and Co³⁺ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H₂ evolution rate of 1.7 μmol h⁻¹ under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.     

Chromophore-Assisted Proximity Labeling of DNA Reveals Chromosomal Organization in Living Cells

The spatial arrangement of chromosome within the nucleus is linked to genome function and gene expression regulation. Existing genome-wide mapping methods often rely on chemically crosslinking DNA with protein baits, which raises concerns of artifacts being introduced during cell fixation. By genetically targeting a photosensitizer protein to specific subnuclear locations, we achieved blue-light-activated labeling of local DNA with a bioorthogonal functional handle for affinity purification and sequence identification through next-generation sequencing. When applied to the nuclear lamina in human embryonic kidney 293T cells, it revealed lamina-associated domains (LADs) that cover 37.6 % of the genome. These LADs overlap with heterochromatin hallmarks and are depleted with CpG islands. This simple labeling method avoids the harsh treatment of chemical crosslinking and is generally applicable to the genome-wide high-resolution mapping of the spatial chromosome organization in living cells.     

ACQ-to-AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two-Photon NIR Bioimaging

The traditional design strategies for highly bright solid-state luminescent materials rely on weakening the intermolecular π–π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid-state fluorescence. TBP-e-TPA with a molecular rotor in the end position of a planar core adopts a long-range cofacial packing mode, which in the solid state is almost non-emissive. By shifting molecular rotors to the bay position, the resultant TBP-b-TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid-state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP-b-TPA nanoparticles were used for two-photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid-state fluorophores.     

Expanding the Synthesis Field of High-Silica Zeolites

Aluminosilicate zeolites are synthesized under hydrothermal conditions in a basic/alkaline medium in the pH range between 9 and 14. The synthesis of MFI-type zeolite in an acidic medium is presented. The critical parameter determining the zeolite formation in an acidic medium was found to be the isoelectric point (IEP) of gel particles. MFI-type zeolite was synthesized above the isoelectric point of the employed silica source, where the silica species exhibit a negative charge and the paradigm of zeolite formation based on the electrostatic interaction with the positively charged template is retained. No zeolite formation is observed below the isoelectric point of silica. The impact of aluminum on the zeolite formation is also studied. The results of this study will serve to extend the synthesis field of high silica zeolites to the acidic medium and thus open new opportunities to control the zeolite properties.