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Deactivation Effect Caused by Catalyst-Cocatalyst Pre-contact in Propylene Polymerization with MgCl2-supported Ziegler-Natta Catalyst

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Chinese Journal of Polymer Science 2019年第10期37卷 1023-1030,I0005页

作者： Zhen Zhang Bai-Yu Jiang Biao Zhang Zhi-Sheng Fu Zhi-Qiang Fan Ministry of Education Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University

Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst. The number of active centers([C*]/[Ti])was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and measuring sulfur content in the polymer. The pre-contact treatment caused selective deactivation of a part of active centers with low stereoselectivity and much lower activity in the initial stage of polymerization as compared with the polymerization run without the pre-contact stage. The active center concentration and polymerization activity decreased with prolonging of the pre-contact stage. The proportion of stereoselective active centers was increased by prolonging the pre-contact stage, so the isotacticity of produced polypropylene was enhanced. Release of active centers through catalyst particle fragmentation was significantly retarded, and the polymerization rate curve changed from decay type to induction type by the precontact treatment. In the induction period both non-stereoselective and stereoselective active centers were released and activated, resulting in gradual reduction of the polymer’s isotacticity in the first 5-10 min of polymerization. Selective deactivation of non-stereoselective active centers also took place in propylene polymerization using the catalyst without pre-contacting with the cocatalyst. In this case, the polymerization rate decayed with time after a short induction period of 2-5 min. Over reduction of the active center precursors with low stereoselectivity by triethylaluminum was considered as the reason for their deactivation during the pre-contact or the polymerization processes.

关键词： Propylene Polymerization Supported Ziegler-Natta catalyst Cocatalyst Pre-contact

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Ultrafast Volumetric Assembly of Layered Nanocomposites at Dynamic Gelation Interface

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SSRN 2023年

作者： Wang, Yaoguang Zhao, Nifang Shao, Ziyu Wen, Jiaxian Ma, Qiong Gao, Weiwei Bai, Hao State Key Laboratory of Chemical Engineering College of Chemical and Biological Engineering Zhejiang University Hangzhou310027 China Institute of Zhejiang University-Quzhou Quzhou324000 China MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University Hangzhou310027 China

Biomimetic learning has boosted the development of layered nanocomposites with superior mechanical properties, fast ion conduction, high barrier capacities, and high conductivities, resulting in numerous practical applications in artificial structural materials, energy storage, filtration, and electromagnetic shielding. These outstanding properties result from the highly oriented layered structure. Convenient fabrication and complex shapes are required for practical applications. However, conventional strategies, including ice templating, vacuum filtration, and electromagnetic induction, are constrained by time-consuming fabrication and sample shapes, restricting their extension to large-scale applications. Herein, we present a facile, universal, and scalable strategy for fabricating layered nanocomposites using ion diffusion-induced directional gelation. This ultrafast volumetric production, including controllable thickness growth with no size restriction, results from continuous gelation and convenient post-processing, whose fabrication rate is 21.7 times that of ice templating, 13.2 times that of vacuum filtration, and 3.1 times that of electromagnetic induction. Furthermore, layered alumina/epoxy nanocomposites were prepared with superior specific strength (2.9 MPa m1/2/(Kg/m3)) and specific toughness (96.2 MPa/(Kg/m3)), demonstrating the validity of our strategy for layered structures. Moreover, our approach can be extended to other material systems and arbitrary shapes for multifunctional applications in wearable devices, sensors, and anti-corrosion coatings. © 2023, The Authors. All rights reserved.

关键词： Gelation

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Recent Progress on COS-derived Polymers

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Chinese Journal of Polymer Science 2019年第10期37卷 951-958,I0002页

作者： Cheng-Jian Zhang Xing-Hong Zhang Key Laboratory of Macromolecular Synthesis and Functionalization (Ministry of Education) Department of Polymer Science & Engineering Zhejiang University

The synthesis of sulfur-containing polymer, a very promising functional material, has made a great progress in the past several years. This review is focused on the very recent advances in poly(monothiocarbonate)s derived from carbonyl sulfide(COS) and epoxides including biomass-derived epoxides. Of significance, metal-free catalyst systems, including triethyl borane/Lewis base pair and thiourea/Lewis base pair are developed for the alternating copolymerization of COS with epoxides. Thereof, the thiourea/Lewis base pair is highly active to the copolymerization of COS with epoxide in a living manner. Moreover, a series of crystalline poly(monothiocarbonate)s are presented, including the copolymers derived from COS with oxetane, ethylene oxide, enantiopure epichlorohydrin, and achiral mesoepoxides via enantioselective copolymerization. Based on these COS/epoxide copolymerization process, a variety of COS-based block copolymers with well-defined structure are presented.

关键词： Carbonyl sulfide Epoxide Copolymerization Poly(monothiocarbonate)

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Ionic Liquid-Triggered Charge Regulation of Polydopamine-Based Surface for Antibacterial Nanofiltration

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SSRN 2024年

作者： Zhang, Wen-Ting Zhao, Zi-Yang Jing, Ya-Juan Li, Hao-Nan Cao, Ye Weng, Rui-Bin Wu, Bai-Heng Li, Yongjin Yang, Jing Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education Key Laboratory of Organosilicon Material Technology of Zhejiang Province College of Material Chemistry and Chemical Engineering Hangzhou Normal University No. 2318 Yuhangtang Rd. Hangzhou311121 China MOE Key Laboratory of Macromolecular Synthesis and Functionalization Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province Department of Polymer Science and Engineering Zhejiang University Hangzhou310027 China

The charged surfaces with desirable performance are of high concern in membrane separation but there exist challenges to tailor them over a task-specific range. Herein, we propose an ionic liquid (IL)-triggered charge regulation strategy for polydopamine (PDA)-based surfaces by tuning the number and position of amino groups of ILs. By strategically manipulating the location of amino groups in either the anion, cation, or both, we realize a complete inversion in the surface charge nature of PDA coatings from highly negative to negative and even highly positive (zeta potential: -25 mV to +25 mV), which is attributed to both the number of protonable groups and shielding effect provided by counter ions. Such charge flip enhances Donna effect when the PDA/IL coatings serve as the skin layer of nanofiltration membranes, thereby enabling high rejection to both negative and positive target molecules. Despite charge regulation, ILs with dual amino groups cross link the PDA aggregates, largely narrowing the pore size distribution of the skin layer. The IL cross-linked PDA skin layer with uniform pores thus shows a nearly 100% rejection to the target solutes. Meanwhile, the IL synchronously endow the PDA coatings with tunable charge characteristics, imidazolium functional groups and exceptional superoleophobicity, compensating for the originally inferior antibacterial activity of membranes in a wide pH range © 2024, The Authors. All rights reserved.

关键词： Ionic liquids

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Organocatalytic polymerization

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Science China Chemistry 2019年第9期62卷 1087-1089页

作者： Cheng-Jian Zhang Xing-Hong Zhang Key Laboratory of Macromolecular Synthesis and Functionalization (Ministry of Education) Department of Polymer Science and EngineeringZhejiang University

Organocatalysis, defined as the use of small organic molecules for catalyzing chemical transformations, can be traced back more than a century and has become a thriving area over the past 20 years.

关键词： Organocatalytic polymerization organic molecules catalyzing chemical transformations

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Robust Superhydrophobic Poly(Vinylidene Fluoride) Membranes with Spherulitic Surface Morphology Against Wetting and Scaling in Membrane Distillation

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SSRN 2024年

作者： Han, Minyuan Liu, Gaohui Fang, Chuanjie Zhu, Liping MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University Hangzhou310058 China MOE Engineering Research Center of Membrane and Water Treatment Technology Zhejiang University Hangzhou310058 China Center for Healthcare Materials Shaoxing Institute Zhejiang University Shaoxing312000 China

Membrane distillation (MD) theoretically intercepts salts completely and provides a promising desalination pathway for freshwater supply. However, conventional hydrophobic membranes fail to desalinate water containing surfactants or supersaturated gypsum over a long term. To address wetting and scaling challenges, we developed a superhydrophobization methodology for poly(vinylidene fluoride) membranes by in situ controlling spherulitic surface morphology in thermally induced phase separation. The major advantages of this one-step strategy lie in its fluorination-free, template-free, and nanoparticle-free. The as-prepared membranes exhibit a rough morphology and superhydrophobic character with high air-trapping pockets. The stable vapor fluxes and high salt rejections (> 99%) in the desalination of saline water containing 0.6 mM sodium dodecyl sulfate, 0.03 mM cetyltrimethylammonium bromide, or gypsum solution with a saturation index of 1.1 are achieved. Also, the outstanding anti-wetting and anti-scaling properties aredemonstrated using synthetic shale gas wastewater. The formation of an air layer on the integrated spherulitic surfacehighlights the local kinetic barrier and slippery surface, effectively preventing the attachment of amphiphilic surfactants and mineral ions. More importantly, due to the membrane’s structural integrity, the spherulitic surface displays high robustness and minimal impact from abrasion cycles and ultrasonication. This work exemplifies a facile strategy to engineer micro-/nano-spherulitic surface morphology for robust superhydrophobic membranes used in MD desalination. © 2024, The Authors. All rights reserved.

关键词： Desalination

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Planar Distribution Measurement of Cross-Plane Thermal Diffusivity for Microscale Films

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SSRN 2024年

作者： Zhang, Yanhui Yang, Jie Zhang, Tiantian Liu, Yi Xu, Rui Liu, Yingjun Wang, Jianli Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments Department of Mechanical Engineering Southeast University Nanjing210096 China China Academy of Launch Vehicle Technology Beijing100076 China MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province Zhejiang University 38 Zheda Road Hangzhou310027 China

Thin-film materials are widely used in the field of thermal management, but the characterization of their thermophysical properties on the microscale is still challenging. In this work, the planar distribution of the cross-plane thermal diffusivity for microscale films is measured utilizing the location-variation and frequency-variation methods based on a laser spot heating technique. A laser beam is focused on the film surface for periodic heating, while a thermocouple collects the temperature rise signal from the back surface. The in-plane thermal diffusivity is determined employing the phase lag spatial distribution of the temperature rise. The cross-plane thermal diffusivity is derived after correcting the frequency dependence of phase lag using the bias phase, thereby eliminating the effect of thermal contact resistance at the thermocouple junction. The accuracy of this method is verified by measuring the thermal diffusivity of standard anisotropic polyester and isotropic stainless-steel films. Finally, the cross-plane thermal diffusivity planar distribution of microscale stainless-steel and reduced graphene oxide films are successfully measured, bridging the gap left by the infrared lock-in thermography technique. © 2024, The Authors. All rights reserved.

关键词： Thermal diffusivity

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Conformation tuning of simple non-fused electron acceptors via oxygen and sulfur substitutions and its effects on photovoltaics

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Multifunctional Materials 2021年第2期4卷

作者： Yao, Zhenghui Li, Yaokai Li, Shuixing Shi, Minmin Chen, Hongzheng State Key Laboratory of Silicon Materials Moe Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University Hangzhou310027 China

By altering the number and position of oxygen and sulfur substitutions, four simple non-fused electron acceptors, PTO-4F, PDO-4F, PDS-4F and PTS-4F, were synthesized via feasible two-step reactions. These four acceptors serve as good molecular models to investigate the heteroatom effects on performance of organic solar cells (OSCs) based on their blends with typical polymer donor PBDB-T. The quantity of intramolecular noncovalent bonds, conformation of the molecules and performance of OSCs can be easily adjusted. Gradually increasing oxygen atoms could influence the intramolecular noncovalent (OS, OH) interactions, backbone planarity, film morphology, and electrical and photovoltaic properties significantly. When replacing O atoms with S atoms, the torsional angle of the backbone increases from 3.5 to 97 owing to the reduction of OS attractive coulomb interaction and/or OH hydrogen bonding interaction. With increasing oxygen atom numbers, the absorption is red-shifted gradually and the energy levels are lifted. As a result, the power conversion efficiency of the device increases from 4.06% (PTS-4F) to 6.81% (PTO-4F). This study provides helpful molecular design guideline for the optimization of simple non-fused acceptors and device performances by finely controlling the weak intramolecular noncovalent interactions and molecular conformations. © 2021 IOP Publishing Ltd.

关键词： Hydrogen bonds

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A tarsus construct of a novel branched polyethylene with good elasticity for eyelid reconstruction in vivo

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Regenerative Biomaterials 2020年第3期7卷 259-269页

作者： Peifang Xu Xue Feng Honghao Zheng Zhongwei Feng Zhisheng Fu Changyou Gao Juan Ye Department of Ophthalmology The Second Affiliated Hospital of Zhejiang UniversityCollege of MedicineHangzhouZhejiang 310009China MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou 310027China

Branched polyethylene(B-PE)elastomer was investigated for its potential medical application as a tarsus *** in vitro results showed that the B-PE and processed B-PE films or scaffolds did not exhibit noticeable cytotoxicity to the NIH3T3 fibroblasts and human vascular endothelial cells(ECs).The B-PE scaffolds with a pore size of 280–480 mm were prepared by using a gelatin porogen-leaching *** porous scaffolds implanted subcutaneously in rats exhibited mild inflammatory response,collagen deposition and fast fibrovascularization,suggesting their good *** real-time PCR analysis showed low expression of pro-inflammatory genes and up-regulated expressions of collagen deposition and vascularization-related genes,validating the results of historical evaluation in a molecular *** B-PE scaffolds and Medpor controls were transplanted in rabbits with eyelid *** B-PE scaffolds exhibited a similar elastic modulus and provided desirable repair effects with mild fibrous capsulation,less eyelid deformities,and were well integrated with the fibrovascular tissue compared with the Medpor controls.

关键词： branched polyethylene elasticity scaffolds fibrovascularization eyelid reconstruction

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Dynamically softened substrate regulates malignancy of breast tumor cells

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Science China Materials 2021年第10期64卷 2580-2592页

作者： Mi Hu Xu Li Wei-Pin Huang Deng-Feng Hu Ke-Feng Ren Jian Ji MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou 310027China Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province Sir Run Run Shaw HospitalZhejiang UniversityHangzhou 310016China

It has long been hypothesized that an increase in the extracellular matrix(ECM)stiffness mechanoactivates malignant phenotypes of breast tumor cells by regulating an array of processes underlying cancer *** the contribution of substrate stiffening to drive malignant phenotype traits and other biological functions of a tumor is increasingly understood,the functional role of substrate softening on breast cancer cellular responses has rarely been ***,we employed matrix metalloproteinase(MMP)-sensitive film to perform assays to explore the consequences of lowering stiffness on the biological behaviors of breast cancer cell *** demonstrated that cells underwent dramatic changes in migration,cellular conjunction,and expression of malignance-associated proteins and genes when the substrate stiffness *** on RNA sequencing and analysis,we found that hub genes including TP53,CCND1,MYC,CTNNB1,and YAP were validated to play central parts in regulating stiffness-dependent cellular manner ***,through visualization of differentially expressed genes(DEGs),cells on dynamically softened substrate appeared less influenced by transfer to tissue culture polystyrene(TCPS).These results suggest substrates with decreasing stiffness could normalize breast tumor malignant phenotype and help cells store the mechanical memory of the consequential weaker malignance.

关键词： substrate stiffness dynamic softening breast tumor cell malignance normalization

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