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Effects of thiocyanate anions on switching and structure of poly(N-isopropylacrylamide) brushes

Chinese Physics B 2019年第6期28卷 262-269页

作者： Xin-Jun Zhao Zhi-Fu Gao Xinjiang Laboratory of Phase Transitions and Microstructures of Condensed Matter Physics Yili Normal UniversityYining 835000China Laboratory of Micro-Nano Electro Biosensors and Bionic Devices Yili Normal UniversityYining 835000China Xinjiang Astronomical Observatory Chinese Academy of Sciences150Science 1-StreetUrumqi 830011China

In this work, we investigate the effects of thiocyanate anions on the switching and the structure of poly(Nisopropylacrylamide)(PNIPAM) brushes using a molecular theory. Our model takes into consideration the PNIPAM–anion bonds, the electrostatic effects and their explicit coupling to the PNIPAM conformations. It is found that at low thiocyanate anion concentration, as the anion concentration of thiocyanate increases, thiocyanate anions are more associated with PNIPAM chains through the PNIPAM–anion bonds, which contributes to stronger electrostatic repulsion and leads to an increase of lower critical solution temperature(LCST). By analyzing the average volume fractions of PNIPAM brushes,it is found that the PNIPAM brush presents a plateau structure. Our results show that the thiocyanate anions promote phase segregation due to the PNIPAM–anion bonds and the electrostatic effect. According to our model, the reduction of LCST can be explained as follows: at high thiocyanate anion concentration, with the increase of thiocyanate concentration, more ion bindings occurring between thiocyanate anions and PNIPAM chains will result in the increase of the hydrophobicity of PNIPAM chains;when the increase of electrostatic repulsion is insufficient to overcome the hydrophobic interaction of PNIPAM chains, it will lead to the reduction of brush height and LCST at high thiocyanate anion concentration. Our theoretical results are consistent with the experimental observations, and provide a fundamental understanding of the effects of thiocyanate on the LCST of PNIPAM brushes.

关键词： molecular theory PNIPAM brushes effect of thiocyanate anions

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Numerical Analysis of Tilted Cutting and F128 brushes

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Computer Modeling in Engineering & Sciences 2019年第10期121卷 23-47页

作者： Libardo V.Vanegas-Useche Magd M.Abdel-Wahab Graham A.Parker Facultad de Ingeniería Mecánica Universidad Tecnológica de PereiraLa JulitaPereira 660003Colombia Division of Computational Mechanics Ton Duc Thang UniversityHo Chi Minh CityViet Nam Faculty of Civil Engineering Ton Duc Thang UniversityHo Chi Minh CityViet Nam Soete Laboratory Faculty of Engineering and ArchitectureGhent UniversityTechnologiepark Zwijnaarde 46B-9052 ZwijnaardeBelgium Faculty of Engineering and Physical Sciences University of Surrey.Guildford GU27XHUK.

Road sweeping is an essential service that has to be conducted for public health,as well as aesthetic *** many countries,sweeping vehicles are used for this *** usually comprise a gutter brush that sweeps the debris that is located in the road *** work studies the performance of two kinds of gutter brushes:a cutting brush and a flicking(F128)*** is carried out by means of a 3-D dynamic,nonlinear Finite Element(FE)brush model developed by the *** this model,inertia forces are applied to the bristle,and its clamped end is ***,the surface(road)is rotated,translated,and ***-road interaction is modelled as flexible-to-rigid *** particular,the aim of this article is to compare the performance of a conventional brush and a brush rotating at variable *** brushes normally work tilted,FE analyses are carried out for tilted cutting and F128 brushes,rotating at speeds that fluctuate at different *** is concluded that brush oscillations have a significant effect on bristle tip velocities and bristle-road ***,at certain frequencies,oscillations seem to improve sweeping performance of the F128 ***,they do not appear to improve significantly the performance of the cutting brush.

关键词： Gutter brushes cutting brush flicking brush FEM variable speed brushing

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Miktoarms hyperbranched polymer brushes:One-step fast synthesis by parallel click chemistry and hierarchical self-assembly

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Science China Chemistry 2010年第12期53卷 2461-2471页

作者： HAN Yi & GAO Chao MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering,Zhejiang University,Hangzhou 310027,China 1. MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027 China

Spherical molecular brushes with amphiphilic heteroarms were facilely synthesized by grafting the arms of hydrophobic 2-azidoethyle palmitate and hydrophilic monoazide-terminated poly(ethylene glycol) onto the core of alkyne-modified hyperbranched polyglycerol (HPG) with high molecular weight (Mn=122 kDa) via one-pot parallel click *** parallel click grafting strategy was demonstrated to be highly efficient (～100%),very fast (～ 2 h) and well controllable to the amphilicity of molecular *** adjusting the feeding ratio of hydrophobic and hydrophilic arms,a series of brushes with different arm ratios were readily *** resulting miktoarms hyperbranched polymer brushes (HPG-g-C16/PEG350) were characterized by hydrogen-nuclear magnetic resonance (1H NMR),Fourier transform infrared (FT-IR) spectroscopy,gel permeation chromatography (GPC),and differential scanning calorimetry (DSC) *** spherical molecular brushes showed high molecular weights up to 230 kDa,and thus could be visualized by atomic force microscopy (AFM).AFM and dynamic laser light scattering (DLS) were employed to investigate the self-assembly properties of amphiphilic molecular brushes with closed proportion of hydrophobic and hydrophilic *** brushes could self-assemble hierarchically into spherical micelles,and network-like fibre structures,and again spherical micelles by addition of n-hexane into the dichloromethane or chloroform solution of *** addition,this kind of miktoarms polymer brush also showed the ability of dye loading via host-guest encapsulation,which promises the potential application of spherical molecular brushes in supramolecular chemistry.

关键词： miktoarms molecular brushes hyperbranched polyglycerol amphiphilic self-assembly

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Enhancing the ionic conductivity in a composite polymer electrolyte with ceramic nanoparticles anchored to charged polymer brushes

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Chinese Chemical Letters 2020年第3期31卷 831-835页

作者： Bintao Zhao Xi Lu Qian Wang Jingfa Yang Jiang Zhao Henghui Zhou College of Chemistry and Molecular Engineering Peking UniversityBeijing 100871China Pulead Technology Industry Co.Ltd. Beijing 102200China Institute of Chemistry Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Polymer electrolytes a re essential for next-gene ration lithium batteries because of their excellent safety ***,low ionic conductivity is the main obstacle restricting their commercial *** with nanoparticles are a promising route to overcome this *** this work,lithium polystyrene sulfonate brushes(LiPSS)is anchored to silicon dioxide nanoparticles with chemical bonding using atom transfer radial polymerization(SI-ATRP).The composite polymer electrolytes are made by mixing vinylene carbonate and nanoparticles via a facile in situ polymerization *** ionic conductivity of composite polymer electrolytes is improved to 7.2×10^-4 S/cm at room temperature,which is attributed to the low degree of crystallinity of polymer electrolyte and the fast ion transport on the surfaces of polymer brush layers that act as a conductive *** composite polymer electrolytes show a wide electrochemical window of approximately 4.5 V ***^+/Li and excellent cycling performance retention of approximately 95%after 100 cycles at ambient *** results also prove that surface groups of ceramic na noparticles are an important way to increase the electrochemical properties of composite polymer electrolytes.

关键词： Polymer electrolyte Polymer brushes Solid batteries Nanoparticles Composite electrolyte

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Controlled synthesis of silver nanoparticles from polyoxometalates-immobilized poly(4-vinylpyridine) brushes

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Chinese Chemical Letters 2019年第5期30卷 1097-1099页

作者： Hang Bian Xuejian Zhang Hongkai Zhao Ning Zhang School of Material Science and Engineering Jilin Jianzhu UniversityChangchun 130118China Department of Chemistry Northeast Normal UniversityChangchun 130024China

This contribution reports the immobilization of polyoxometalate(POM)into poly(4-vinyl pyridine)(P4 VP)brushes and the controlled reduction of silver ions,in-situ generating metal nanoparticles in the brushes.P4 VP brushes were straightforwardly created by UV-assisted photopolymerization of 4-vinyl pyridine(4VP)on silicon or glass *** acid(H3 PW12 O40),one of the most widely used Keggin-type POM was anchored onto these pyridine moieties through electrostatic interaction,leading to the P4 VP/POM hybrid *** immobilized POM was further reduced to heteropolyblue,which could be used to generate silver nanoparticles in a controlled ***,UV-vis and IR characterization indicate that P4 VP brushes not only provide an efficient platform in the controlled preparation of Ag nanoparticles,but also efficiently disperse and stabilize POM,thus preventing the aggregation of the generated Ag nanoparticles.

关键词： Polymer brushes Polyoxometalate Ag nanoparticles Grafting polymerization

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Novel Hyperbranched Polyurethane brushes for Biomedical Applications

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复旦学报（自然科学版） 2007年第5期46卷 612-,616页

作者： Ton Loontjens Bart Plum University of Groningen Nijenborgh 4 9747AGGroningen the NetherlandsDSM research Urmonderbaan 22 6160MDGeleen the Neterhlands DSM research Urmonderbaan 22 6160MDGeleen the Neterhlands

1 Results The objective was to make hyperbranched (HB) polyurethane brushes with reactive end groups, to coat biomedical devices and to enable the introduction of various functionalities that are needed to fulfill biomedical *** materials should fulfill at least three requirements: (1) good mechanical properties, (2) good biocompatibility and (3) provided with functionalities to perform the required tasks. Since polyurethanes are able to fulfill the first 2 requirements we focused in this w...

关键词： hyperbranched brushes biomedical blocked isocyanates polyurethanes/urea

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Selective modification of two-dimensional MoS_2 nanosheets by polymer grafting

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Chinese Chemical Letters 2019年第2期30卷 311-313页

作者： Hang Bian Xuejian Zhang Dexin Huang Ning Zhang School of Material Science and Engineering Jilin Jianzhu University Key Laboratory of Synthetic Rubber Changchun Institute of Applied ChemistryChinese Academy of Sciences

As an emerging two-dimensional (2D) nanomaterial, single layer ora few layers of molybdenum disulfide (MoS_2) has drawn significant attention in the past decade. In the present work, we report a strategy in direct creating polymer brushes on MoS_2 surfaces via S—C bond in the presence of UV light. The modification of MoS_2 nanosheets can be achieved bilaterally or homolaterally by performing the UVgrafting polymerization on exfoliated MoS_2 nanosheets or a single layer of MoS_2 deposited on a silicon substrate. A series of vinyl monomers including methyl methacrylate (MMA), styrene (St) and 2-isopropenyl-2-oxazoline (IPOx) could be applied to this approach, leading to the formation of poly (methyl methacrylate) (PMMA), polystyrene (PS) and poly (2-isopropenyl-2-oxazoline) (PIPOx) ***, IR, and XPS characterizations indicate the successful formation of homogeneous brush layers on MoS_2 surfaces. The polymer brushes modified MoS_2 may found potential applications in photo dynamic therapy and sensing technologies.

关键词： Molybdenum disulfide Polymer brushes SIPGP Surface modification S-C bond

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