Highly Efficient Depolymerization of Waste Polyesters Enabled by Transesterification/Hydrogenation Relay Under Mild Conditions

The efficient depolymerization of polyesters under mild conditions remains a significant challenge. Herein, we demonstrate a highly efficient strategy for the degradation of a diverse array of waste polyesters as low to 80 °C, 1 bar H₂. The key to the success of this transformation relied on the initial transesterification of macromolecular polyester into more degradable oligomeric fragments in the presence of CH₃OH and the subsequent hydrogenation by the use of the rationally designed quinaldine-based Ru complex. Controlled experiments and preliminary mechanistic studies disclosed the quinaldine-based catalysts could be hydrogenated to the eventually active species, which has been confirmed by X-ray diffraction analysis and directly used as a catalyst in the hydrogenolysis of polyester. The strong viability and high activity of this new species in protic solvent were explained in detail. Besides, the crucial role of CH₃OH in promoting reaction efficiency during the whole process was also elucidated. The synthetic utility of this method was further illustrated by preparing 1,4-cyclohexanedimethanol (CHDM) from waste polyethylene terephthalate (PET).     

Solvent-Free Chemical Recycling of Polymethacrylates made by ATRP and RAFT polymerization: High-Yielding Depolymerization at Low Temperatures

Although controlled radical polymerization is an excellent tool to make precision polymeric materials, reversal of the process to retrieve the starting monomer is far less explored despite the significance of chemical recycling. Here, we investigate the bulk depolymerization of RAFT and ATRP-synthesized polymers under identical conditions. RAFT-synthesized polymers undergo a relatively low-temperature solvent-free depolymerization back to monomer thanks to the partial in situ transformation of the RAFT end-group to macromonomer. Instead, ATRP-synthesized polymers can only depolymerize at significantly higher temperatures (>350 °C) through random backbone scission. To aid a more complete depolymerization at even lower temperatures, we performed a facile and quantitative end-group modification strategy in which both ATRP and RAFT end-groups were successfully converted to macromonomers. The macromonomers triggered a lower temperature bulk depolymerization with an onset at 150 °C yielding up to 90 % of monomer regeneration. The versatility of the methodology was demonstrated by a scalable depolymerization (≈10 g of starting polymer) retrieving 84 % of the starting monomer intact which could be subsequently used for further polymerization. This work presents a new low-energy approach for depolymerizing controlled radical polymers and creates many future opportunities as high-yielding, solvent-free and scalable depolymerization methods are sought.     

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.     

Interfacial Engineering for Efficient Low-Temperature Flexible Perovskite Solar Cells

Photovoltaic technology with low weight, high specific power in cold environments, and compatibility with flexible fabrication is highly desired for near-space vehicles and polar region applications. Herein, we demonstrate efficient low-temperature flexible perovskite solar cells by improving the interfacial contact between electron-transport layer (ETL) and perovskite layer. We find that the adsorbed oxygen active sites and oxygen vacancies of flexible tin oxide (SnO₂) ETL layer can be effectively decreased by incorporating a trace amount of titanium tetrachloride (TiCl₄). The effective defects elimination at the interfacial increases the electron mobility of flexible SnO₂ layer, regulates band alignment at the perovskite/SnO₂ interface, induces larger perovskite crystal growth, and improves charge collection efficiency in a complete solar cell. Correspondingly, the improved interfacial contact transforms into high-performance solar cells under one-sun illumination (AM 1.5G) with efficiencies up to 23.7 % at 218 K, which might open up a new era of application of this emerging flexible photovoltaic technology to low-temperature environments such as near-space and polar regions.     

结晶度对微波作用下PET水解解聚的影响

本文对微波作用下PET的中性水解解聚反应中原料结晶度的影响进行了研究.     

Depolymerization of polysilicic acid by tiron

As a preliminary experiment for the development of an effective silica scale inhibitor at geothermal power plants, the effect of tiron, a ligand to monosilicic acid, on the polymerization of silicic acid was investigated by gel chromatographic method. The experiments were carried out at Si concentration of 400 ppm (14 mM) and at pH 8 where are a similar condition to geothermal water. The tiron concentration was varied (0-50 mM). At 30 mM of tiron, the polymerization of silicic acid occurred rapidly within first 1 h in spite of the presence of tiron, however, polysilicic acids were depolymerized by tiron. The depolymerization mechanism of polysilicic acids was discussed based on zeta potentials for silica gel particles in the absence and presence of tiron.     

Depolymerization of hyaluronate by the phototoxic drugs phenothiazines and sulfacetamide

Phenothiazines (promazine, promethazine, chlorpromazine) and sulfacetamide, known as phototoxic drugs, depolymerize aqueous sodium hyaluronate (HA) on exposure to light. The reduction in the HA molecular weight was followed by size-exclusion chromatography with low-angle laser light scattering. In the low-concentration region of the drugs below 0.05 mM, the rate constants of depolymerization increased. The molecular weight of HA was practically unchanged without UV irradiation in the presence of drugs or with UV irradiation in the absence of drugs, indicating the phenothiazines and sulfacetamide require photoenergy to yield any kind of damaging chemical species for HA depolymerization. An involvement of active oxygen radicals in the effects of promazine and promethazine was evidenced by inhibition under anaerobic conditions. Further, addition of mannitol controlled the reaction in the presence of oxygen, pointing to hydroxyl radicals as the damaging agent. Chlorpromazine and sulfacetamide preferably depolymerized HA under anaerobic conditions, suggesting the participation of hydrated electrons. Received: 14 July 1999/Accepted in revised form: 7 September 1999     

Regulating Perovskite Crystallization through Interfacial Engineering Using a Zwitterionic Additive Potassium Sulfamate for Efficient Pure-Blue Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) perovskites are emerging as efficient emitters in blue perovskite light-emitting diodes (PeLEDs), while the imbalanced crystallization of the halide-mixed system limits further improvements in device performance. The rapid crystallization caused by Cl doping produces massive defects at the interface, leading to aggravated non-radiative recombination. Meanwhile, unmanageable perovskite crystallization is prone to facilitate the formation of nonuniform low-dimensional phases, which results in energy loss during the exciton transfer process. Here, we propose a multifunctional interface engineering for nucleation and phase regulation by incorporating the zwitterionic additive potassium sulfamate into the hole transport layer. By using potassium ions (K⁺) as heterogeneous nucleation seeds, finely controlled growth of interfacial K⁺-guided grains is achieved. The sulfamate ions can simultaneously regulate the phase distribution and passivate defects through coordination interactions with undercoordinated lead atoms. Consequently, such synergistic effect constructs quasi-2D blue perovskite films with smooth energy landscape and reduced trap states, leading to pure-blue PeLEDs with a maximum external quantum efficiency (EQE) of 17.32 %, spectrally stable emission at 478 nm and the prolonged operational lifetime. This work provides a unique guide to comprehensively regulate the halide-mixed blue perovskite crystallization by manipulating the characteristics of grain-growth substrate.     

Complete Depolymerization of PET Wastes by an Evolved PET Hydrolase from Directed Evolution

PETase displays great potential in PET depolymerization. Directed evolution has been limited to engineer PETase due to the lack of high-throughput screening assay. In this study, a novel fluorescence-based high-throughput screening assay employing a newly designed substrate, bis (2-hydroxyethyl) 2-hydroxyterephthalate (termed BHET-OH), was developed for PET hydrolases. The best variant DepoPETase produced 1407-fold more products towards amorphous PET film at 50 °C and showed a 23.3 °C higher T_m value than the PETase WT. DepoPETase enabled complete depolymerization of seven untreated PET wastes and 19.1 g PET waste (0.4 % W_enzyme/W_PET) in liter-scale reactor, suggesting that it is a potential candidate for industrial PET depolymerization processes. The molecular dynamic simulations revealed that the distal substitutions stabilized the loops around the active sites and transmitted the stabilization effect to the active sites through enhancing inter-loop interactions network.     

Interfacial Engineering of Ni/V2O3 Heterostructure Catalyst for Boosting Hydrogen Oxidation Reaction in Alkaline Electrolytes

Alkaline fuel cells can permit the adoption of platinum group metal-free (PGM-free) catalysts and cheap bipolar plates, thus further lowering the cost. With the exploration of PGM-free hydrogen oxidation reaction (HOR) catalysts, nickel-based compounds have been considered as the most promising HOR catalysts in alkali. Here we report an interfacial engineering through the formation of nickel-vanadium oxide (Ni/V₂O₃) heterostructures to activate Ni for efficient HOR catalysis in alkali. The strong electron transfer from Ni to V₂O₃ could modulate the electronic structure of Ni sites. The optimal Ni/V₂O₃ catalyst exhibits a high intrinsic activity of 0.038 mA cm⁻² and outstanding stability. Experimental and theoretical studies reveal that Ni/V₂O₃ interface as the active sites can enable to optimize the hydrogen and hydroxyl bindings, as well as protect metallic Ni from extensive oxidation, thus achieving the notable activity and durability.     

液滴在不互溶液体表面上的相对界面自由能曲面及Neumann三角形的导出

根据系统的界面Helmholtz自由能自发地趋于最低的热力学原理,以浮在不互溶液体(2)表面上透镜状液滴(3)在气(1)、液₂、液₃三相交界处,气-液₃、液₂-液₃界面各自和气-液₂界面通过液滴内部的夹角θ₁、θ₂为变量(0°≤θ₁≤180°,0°≤θ₂≤180°),证明出3个界面张力γ₁₂、γ₁₃、γ₂₃各种可能组合情况下液体₃稳定时的θ₁、θ₂值与它们之间的关系,导出Neumann三角形;并按照计算数据绘出几种类型相对于气相中圆球形液滴的界面自由能曲面图。     

Depolymerization study of sodium hyaluronate by flow field-flow fractionation/multiangle light scattering

Thermal depolymerization of ultrahigh-molecular-weight (UHMW) sodium hyaluronate (NaHA) was studied systematically by using frit-inlet asymmetrical flow field-flow fractionation/multiangle light scattering/differential refractive index (FI-AFlFFF/MALS/DRI). FI-AFlFFF was utilized for the size separation of NaHA samples which had been thermally degraded for varied treatment times, followed by light-scattering detection to determine MW and structural information of degraded NaHA products. Analysis of NaHA products showed time-dependent depolymerization of raw molecules into smaller-MW components, as well as unfolding of compact structures of UHMW NaHA. To determine whether the observed decrease in MW of sodium hyaluronate originated from the chain degradation of UHMW molecules or from dissociation of entangled complex particles that may have been formed by intermolecular association, narrow size fractions (1 × 10⁷–6 × 10⁷ and >6 × 10⁷ MW) of NaHA molecules were collected during FlFFF separation and followed by thermal treatment. Subsequent FI-AFlFFF/MALS analysis of collected fractions after thermal treatment suggested that the ultrahigh-MW region (>10⁷ Da) of NaHA is likely to result from supermolecular structures formed by aggregation of large molecules.     

有机电致发光器件的结构、发光机理及表面工程

简要介绍有机电致发光器件(OLED)的结构、发光机理、表面工程及检测、有机-无机电致发光材料的复合及制备技术。     

界面张力弛豫法研究不同分子量原油活性组分界面扩张粘弹性

采用界面张力弛豫法研究了不同分子量原油活性组分在正癸烷-水界面上的扩张粘弹性质,阐述了界面扩张模量的弹性和粘性随扩张频率的变化规律.研究发现,随着原油活性组分分子量的增大,极限扩张粘度明显增大,而极限扩张弹性逐渐增大;当分子量大于某一数值后,极限扩张弹性变化不明显.对界面张力弛豫实验结果进行拟合得到的参数表明,界面上和界面附近的微观弛豫过程的数目随原油活性组分分子量的增加而增加,弛豫过程的特征频率也呈规律性变化.不同原油活性组分的界面扩张粘弹性质可从其不同特征的微观弛豫过程得到解释.     

界面聚合法制备复合膜中的改性研究

介绍了复合膜的结构及性能,阐述了界面聚合法的基本原理及用该法制备复合膜的优越性;同时重点综述了国内外对复合膜的性能如通量和截留率、耐氯性、热稳定性、耐溶剂性和抗污染性的研究现状及改进方法,并对界面聚合法制备复合膜存在的问题以及研究前景进行了展望。     

Interfacial deposition of functionalized copolymers onto nanoemulsions produced by the solvent displacement method

Cationic nanoemulsions containing an oily core as potential carriers of nucleic acids were prepared by a solvent displacement method in the presence of a nonionic surfactant (Pluronic F68). With a view to functionalize such nanoemulsions for further incorporation of a fusogenic peptide, a poly(maleic anhydride-alt-methyl vinyl ether) (M _n=67,000) grafted with variable amount of acetylspermine (or acetylspermidine) and decylamine was nanodeposited during the nanoemulsion formation step. Functionalized nanoemulsions were characterized in terms of particle size (by quasi-elastic light scattering and electron microscopy), electrophoretic mobility and long-term stability as a function of the amount of polymer used in the formulation. It was found that increases in the level of the copolymer led to a reduction in the particle size and a decrease in colloidal stability. In addition, the incorporation of the grafted copolymers at the interface of the nanoemulsions was clearly evidenced, a shift towards low pH at the point of zero charge being attributed to the formation of carboxylic groups induced by hydrolysis of the residual maleic anhydride groups of the copolymer. Received: 1 September 2000 / in revised form: 29 November 2000 Accepted: 12 December 2000     

界面聚合法制备正二十烷微胶囊化相变储热材料

采用界面聚合的方法, 以甲苯鄄2,4-二异氰酸酯(TDI)和乙二胺(EDA)为反应单体, 非离子表面活性剂聚乙二醇壬基苯基醚(OP)为乳化剂, 合成了正二十烷为相变材料的聚脲包覆微胶囊. 结果表明, 二异氰酸酯和乙二胺按质量比1.9:1 进行反应. 以透射电镜和激光粒度分析仪分析微胶囊, 测得空心微胶囊直径约为0.2 μm, 含正二十烷微胶囊约为2-6 μm. 红外光谱分析证明, 壁材料聚脲是由TDI 及EDA 两种单体形成的. 正二十烷的包裹效率约为75%. 微胶囊的熔点接近囊芯二十烷的熔点, 而其储热量在壁材固定时随囊芯的量而变. 热重分析表明, 囊芯正二十烷、含正二十烷的微胶囊以及壁材料聚脲, 能够耐受的温度分别约为130 ℃、170 ℃及270 ℃.     

Reversible Zn Metal Anodes Enabled by Trace Amounts of Underpotential Deposition Initiators

Routine electrolyte additives are not effective enough for uniform zinc (Zn) deposition, because they are hard to proactively guide atomic-level Zn deposition. Here, based on underpotential deposition (UPD), we propose an “escort effect” of electrolyte additives for uniform Zn deposition at the atomic level. With nickel ion (Ni²⁺) additives, we found that metallic Ni deposits preferentially and triggers the UPD of Zn on Ni. This facilitates firm nucleation and uniform growth of Zn while suppressing side reactions. Besides, Ni dissolves back into the electrolyte after Zn stripping with no influence on interfacial charge transfer resistance. Consequently, the optimized cell operates for over 900 h at 1 mA cm⁻² (more than 4 times longer than the blank one). Moreover, the universality of “escort effect” is identified by using Cr³⁺ and Co²⁺ additives. This work would inspire a wide range of atomic-level principles by controlling interfacial electrochemistry for various metal batteries.     

界面张力弛豫法研究不同结构破乳剂油水界面扩张粘弹性

采用界面张力弛豫法研究了支链破乳剂AE121和直链破乳剂SP169在正癸烷-水界面上的扩张粘弹性质，并与小幅周期振荡法获得的结果进行了比较.阐述了两种破乳剂的扩张模量随扩张频率和破乳剂浓度的变化规律.研究发现，在低频率处，两种破乳剂的扩张模量均接近于零；在中间频率范围内，扩张模量随扩张频率的增加而增大；在高频率处，扩张模量的幅度接近于极限扩张弹性.在中间频率范围内，扩张模量随破乳剂浓度增大，在接近临界胶束浓度处出现一个极大值；同时还发现，界面上和界面附近的微观弛豫过程的数目随破乳剂浓度增加而增大，其贡献也呈规律性变化.     

界面聚合法合成聚吡咯甲烷微球及其影响因素研究

采用吡咯和对二甲氨基苯甲醛通过酸催化静态界面聚合的方法得到了聚[吡咯-2,5-二(对二甲氨基苯甲烷)]微球。通过扫描电镜分析．研究了酸催化剂种类、浓度和反应温度对成球的影响。红外光谱分析表明得到的聚合物具有类似开环卟啉的结构。