Liquid-like polymer lubricating surfaces:Mechanism and applications

Liquid-like polymer lubricating surfaces(LPLSs)are solid substrates with highly flexible polymer chains grafted via covalent bonds.This unique modification enables ultralow contact-angle hysteresis,repellency of various liquids and bulk ice,and stability.The distinctive wettability and universality of LPLSs have potential applications in liquid motion,biological detection,and environmental protection.In this review,we summarize the mechanisms,preparation,and applications of LPLSs.We discuss the wettability and lubrication mechanisms of liquid droplets on LPLSs.We then categorize LPLS fabrication into“grafted onto”and“grafted from”groups,depending on the type of polymer.We highlight representative applications with recent developments in anti-complex liquid,anti-icing,anti-biological adhesions,biosensing,and photocatalytic activity.Finally,we discuss future challenges and outlooks for LPLSs.

Green Synthesized Liquid-like Dynamic Polymer Chains with Decreased Nonspecific Adhesivity for High-Purity Capture of Circulating Tumor Cells

The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabilities of the capture surfaces,which critically hampers the efficiency and purity of the captured CTCs.Herein,we propose a liquid-like interface design strategy that consists of liquid-like polymer chains and anti-EpCAM modification processes for high-purity and high-efficiency capture of CTCs.The dynamic flexible feature of the liquid-like chains endows the modified surfaces with excellent antiadhesion property for proteins and blood cells.The liquid-like surfaces can capture the target CTCs and show high cell viability due to the environmentfriendly surface modification processes.When liquid-like surface designs were introduced in the deterministic lateral displacement(DLD)-patterned microfluidic chip,the nonspecific adhesion rate of WBCs was reduced by more than fivefold compared to that in the DLD chip without liquid-like interface design,while maintaining comparable capture efficiency.Overall,this strategy provides a novel perspective on surface design for achieving high purity and efficient capture of CTCs.

Synthesis of PMMA-co-PMAA Copolymer Brush on Multi-Wall Carbon Nanotubes

Poly(methyl methacrylate)/poly(methacrylamide) copolymer (PMMA-co-PMAA) was synthesized by a free radical copolymerization of MMA and MAA monomers in methylethyl ketone using AIBN as radical initiator. Multi-wall carbon nanotubes (MWCNT) were oxidized in KMnO4 acidic suspension. Carboxyl groups on the surface oxidized MWCNT were reacted with primary amide group of PMMA-co-PMAA copolymer in MEK solution under ultrasound to form polymer brush on the surface of MWCNT. With the help of TG analyses the amount of covalently grafted PMMA-co-PMAA copolymer onto MWCNT surface was determined as ?47 wt%. TEM analyses identified thin co-polymer layer adhered onto MWCNT surface with average thickness ?5 nm.

Influence of Solvent Size on Structural Properties of Bottle-brush Polymers

We proposed a modified dissipative particle dynamics simulation model by which one can effectively avoid the bond-crossing problem, and investigated the effect of solvent size on the structural properties of bottle-brush polymers in dilute solution on the basis of this model. It was found that with the increase of solvent size, the radius of the gyration of the bottle-brush polymer decreases considerably in the athermal solvent but increases in the selective solvent favoring the backbone, respectively.

Self-healable and Robust Film Based on Electroactive Polymer Brush as Electrode for Flexible Supercapacitor

The aim of this study was to develop self-healable and robust elect roconductive film based on polyaniline copolymer for application as electrode in flexible supercapacitor.For this purpose,the electroconductive polymer brushes(EPB)was elaborated.The synthesis of EPB is based on graft polymerizations of acrylamide(AAm)on poly(vinyl alcohol)(PVA)with formation of PVA-PAAm polymer brush and subsequent graft copolymerization of aniline and p-phenylenediamine on PVA-PAAm resulting in formation of EPB with electroconducting copoly(aniline-co-pphenylenediamine)(PAPh DA).It was found that the ratio between PVA and PAAm at the first stage greatly influence the electrochemical performance of the EPBs.Electroconducting films were prepared by casting of EPB solution with subsequent drying.Investigation of electrical current distribution through the film with AFM reveal more uniform distribution of PAPhDA in EPB in comparison with reference PVA-PAPhDA and PAAm-PAPhDA samples.It was demonstrated that mechanical cha racteristics and electrical conductivity values of films restore at large extent after curring and self-healing under optimal relative humidity level(58%).The flexile supercapacitor cell with EPB film electrodes demon strate specific capacitance 602 mF·cm^(-2)at the current density of 1 mA·cm^(-2)and retention 94%of initial capacitance after 5000 charge/discharge cycles.

Friction between Strongly Compressed Polymer Brushes

We present the results of molecular dynamics simulations of steady shear between a pair of neutral polymer brushes,as well as a pair of charged polymer brushes in the strongly compressed regime.The results of the molecular dynamic simulations of neutral and polyelectrolyte brushes in implicit solvent including normal forces,shear forces,viscosities and friction coefficients as a function of separation between brushes,are presented in the study.The comparison of the simulation results of neutral and charged brushes shows that the charged brushes is in the quasi-neutral regime,and the dependence of viscosity on the separation distance show the similar power law of neutral brushes.Our simulation results confirm that the implicit solvent simulations of polyelectrolyte brushes that ignore hydrodynamics interaction are in agreement with the scaling predictions qualitatively because of screening of hydrodynamic interaction and long-range electrostatic interactions on the correlation length scale.Both of neutral and charged brushes show the lubrication properties that the friction coefficient decreases with the separation decreases at enough large loads.However,a maximum of friction coefficients is observed for polyelectrolyte brushes,which is in contrast to the neutral brushes with monotonical dependence.

Oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient friction and wear reduction

Nanomaterials as lubricating oil additives have attracted significant attention because of their designable composition and structure,suitable mechanical property,and tunable surface functionalities.However,the poor compatibility between nanomaterials and base oil limits their further applications.In this work,we demonstrated oil-soluble poly(lauryl methacrylate)(PLMA)brushes-grafted metal-organic frameworks nanoparticles(nanoMOFs)as lubricating oil additives that can achieve efficient friction reduction and anti-wear performance.Macroinitiators were synthesized by free-radical polymerization,which was coordinatively grafted onto the surface of the UiO-67 nanoparticles.Then,PLMA brushes were grown on the macroinitiator-modified UiO-67 by surface-initiated atom transfer radical polymerization,which greatly improved the lipophilic property of the UiO-67 nanoparticles and significantly enhanced the colloidal stability and long-term dispersity in both non-polar solvent and base oil.By adding UiO-67@PLMA nanoparticles into the 500 SN base oil,coefficient of friction and wear volume reductions of 45.3%and 75.5%were achieved due to their excellent mechanical properties and oil dispersibility.Moreover,the load-carrying capacity of 500 SN was greatly increased from 100 to 500 N by the UiO-67@PLMA additives,and their excellent tribological performance was demonstrated even at a high friction frequency of 65 Hz and high temperature of 120℃.Our work highlights oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient lubricating additives.

Tuning Polymer-Grafted Particle Monolayer Structure at the Air-Water Interface by Introducing Anisotropic Features

Fabrication of anisotropic material is one of the important topics and we examined to introduce “anisotropic” nature by spreading polymer-grafted particle on the medium with polymer-reactive potential. Poly (tert-butyl methacrylate) (PtBMA) was polymerized from polystyrene latex (PSL) surface by ATRP to give PtBMA-grafted PSL (PSL-PtBMA). Particle monolayer was formed at air-water and air-acidic water interfaces and the monolayer characteristics were compared by π-A isotherm measurements, SEM observations, and contact angle measurements. π-A isotherms, in particular, indicates that the interaction between polymer chains become stronger by changing the subphase condition, which suggests that anisotropicparticle monolayer formation.

亲水、疏水聚合物刷水润滑机制的对比研究

通过表面接枝聚合技术在摩擦副表面(陶瓷球-玻璃盘)分别生长亲、疏水型2种聚合物刷:聚甲基丙烯酸-3-磺酸丙酯钾盐(PSPMA)和聚甲基丙烯酸月桂酯(PLMA),成功构筑了润湿性不同的2种浸润表面,利用球-盘式光干涉薄膜测量装置研究了2种表面在水环境中的液膜厚度和摩擦力变化,结果表明2种表面呈现出不同的减摩效果:PLMA表面的摩擦力稳定且随速度变化较小,推测这与其较低的表面自由能和低玻璃化温度有关;PSPMA表面的摩擦系数波动较大且滑滚比和卷吸速度对其影响较大,这可能与聚合物刷发生高度水化而在接触表面形成了1层具有法向承载能力的水合层有关.亲水的PSPMA表面形成的水膜膜厚要远远高于疏水的PLMA表面水膜.高速滑动条件下,在流体动压效应和水合作用共同耦合作用使得PSPMA表面呈现出了润滑增强作用,从而获得了较高的膜厚和较低的摩擦系数.研究表明聚合物刷的水合效应对于获取优异的润滑性能是至关重要的,这对于理解水基润滑的机理和指导水润滑材料的设计具有较为重要的意义.

水合作用与 pH 调控两性离子聚合物刷的相变行为

本文基于Flory-Huggins理论,建立理论模型研究水合作用与pH调控两性离子聚合物(ZP)刷的相变行为.理论模型考虑ZP的水合作用,以及ZP刷体系中的静电作用.研究发现,在不同pH条件下,ZP刷的体积分数随着水合作的减弱而的增加.随着pH的变化,ZP刷构象随着水合性转变行为明显改变,这是由于pH调控ZP链单体带有过多的净电荷(正电荷或负电荷),致使ZP链内出现静电排斥导致ZP刷溶胀.另外,当ZP链单体呈现过多的净电荷,会在很大程度上决定ZP刷体系静电势,影响ZP刷的相变行为.通过考察体系自由能,我们还发现,ZP刷体系自由能呈现了极大值,随着pH值的变化,自由能呈现的极大值随之改变,由此表明了体系的不稳定性,进而导致ZP刷体系发生相变.

针对高分子刷构象转变的自振荡模型

自振荡高分子刷在封闭空间中具有独特的应用.长期以来,由于缺乏理论模型,自振荡高分子刷的物理机制无法被深刻地揭示,其新结构也无法被预测.基于扩散动力学建立高分子刷自振荡的动力学理论模型,通过理论模型方程计算高分子刷的体积分数、高分子单体与溶剂相互作用的势函数,定量确定高分子刷构象转变自振荡的动力学特性,以及高分子单体的Belousov-Zhabotinsky(BZ)反应在诱导高分子刷自振荡过程中的重要作用,获得了高分子刷构象转变的化学波特性,揭示了这种化学波在很大程度上源于BZ反应.理论结果揭示了BZ反应导致化学振荡,在高分子刷内的扩散也是以化学波形式传播,且自振荡的高分子刷还可改变BZ的反应模式.研究结果确定了高分子刷的构象转变的自振荡特性遵守扩散动力学规律.基于所提模型可预言高分子刷体积分数的空间波动特性会导致刷内高分子单体体积分布具有空间不均匀性,令高分子刷内出现结节状结构.研究结果可为设计智能高分子表面材料提供参考.

超支化高分子水基钻井液仿生润滑机理

随着定向钻井技术的发展,水基钻井液润滑性逐渐成为确保定向井钻进的关键指标,设计新型钻井液润滑材料已成为油田化学领域的研究热点和重点。为探究超支化高分子水基钻井液仿生润滑机理,首先采用发散法合成了第1.5代超支化聚丙烯酸乙二胺基丙烯酸十八酯G1.5 P(EDA—MA—OA),然后进行了合成产物结构、微观形貌与热稳定性检测及其强化水基钻井液润滑性能评价,最后系统分析了超支化高分子与膨润土粒子的吸附行为。研究结果表明:①G1.5 P是粒径分布在几十纳米的分散性粒子,具有良好的热稳定性,热解温度集中在214℃;②以G1.5 P为润滑添加剂,构建的水基钻井液润滑系数为0.068,具有良好降摩减磨性;③G1.5 P呈“分子刷”状吸附于亲水材料表面,不仅改变了表面润湿性,而且还可促进膨润土粒子聚结形成致密、韧性的泥饼;④基于超支化高分子强化水基钻井液润滑的构效关系,提出了一种水基钻井液边界—固体润滑新模型,即超支化高分子促进在钻具与井壁摩擦副间形成低剪切强度泥饼,以泥饼结构内摩擦代替钻具刚性外摩擦,实现钻井液降摩减磨功能。结论认为,该认识完善了水基钻井液润滑添加剂的设计思路,为新型高性能润滑处理剂设计及超滑水基钻井液的开发提供了理论与技术支撑。

Microgroove-structured liquid-like surface for liquid discrimination

Discriminating between different liquids using surfaces with special wettability holds significant implications for both fundamental research and practical applications.However,current differentiation surfaces still struggle with challenges such as complex microstructure design,a limited detection range,and poor stability.In this study,we present a new platform for droplet discrimination achieved through a combination of groove structures and a liquid-like polydimethylsiloxane(PDMS)brushes coating.The PDMS brushes coating exhibits excellent stability and low adhesion across a wide range of liquids with surface tensions ranging from 27.5 to 72.8 mN/m,while the groove structure provides distinct energy barriers for droplet sliding.Consequently,liquids with varying surface tensions can be effectively discriminated,as evidenced by the increased sliding angles(SAs)observed as liquids with lower surface tension moving across the groove.Furthermore,we utilized a three dimensional(3D)model of the droplet developed using Surface Evolver,and conducted energy variation calculations during droplet sliding across the groove to analyze the SA differences among liquids with different surface tensions.Additionally,we proposed two simple differentiation platforms that successfully demonstrated effective droplet discrimination.This work introduces a novel strategy for droplet discrimination,offering innovative ideas for the design of functional surfaces.These findings may potentially be applied in other fields involving droplet manipulation,such as droplet-based microchemical reactions and bio-detection.

Simultaneous Bulk-and Surface-initiated Living Polymerization Studied with a Heterogeneous Stochastic Reaction Model

To better characterize the properties of surface-initiated polymers, simultaneous bulk-and surface-initiated polymerizations are usually carried out by assuming that the properties of the surface-initiated polymers resemble those of the bulk-initiated polymers. Through a Monte Carlo simulation using a heterogeneous stochastic reaction model, it was discovered that the bulk-initiated polymers exhibit a higher molecular weight and a lower dispersity than the corresponding surface-initiated polymers, which indicates that the equivalent assumption is invalid. Furthermore, the molecular weight distributions of the two types of polymers are also different, suggesting different polymerization mechanisms. The results can be simply explained by the heterogeneous distributions of reactants in the system. This study is helpful to better understand surface-initiated polymerization.

全氟乙烯基醚类单体的自由基共聚合、基于“SuFEx”点击反应的后修饰及其性能

首先在常压和非氟溶剂中通过自由基热引发共聚合制备了6种全氟乙烯基醚类单体与非氟乙烯基醚类单体的共聚物,然后经“SuFEx”点击反应进行功能化修饰制得聚合物分子刷,进一步通过透析法构筑高含氟量的聚合物纳米粒子。利用傅里叶变换红外光谱(FT-IR)、核磁共振氟谱(^(19)F-NMR)、核磁共振氢谱(^(1)H-NMR)差示扫描量热分析(DSC)和凝胶渗透色谱(GPC)等详细表征了含氟聚合物的结构、接枝率及物化性能,证明全氟乙烯基醚类单体与非氟乙烯基醚类单体共聚合得到交替共聚物,与乙酸乙烯酯单体共聚合得到无规共聚物。同时“SuFEx”点击反应可以实现磺酰氟(―SO_(2)F)共聚物侧链的高效接枝。紫外-可见分光光度计(UV-Vis)、动态光散射(DLS)和透射电镜(TEM)分析表明,两亲性氟化共聚物自组装形成了流体力学粒径120 nm左右的球形胶束状聚集体,且具有较低的临界聚集浓度。

PIEZOELECTRIC PROPERTIES OF SINGLE-STRAND DNA MOLECULAR BRUSH BIOLAYERS

The paper is devoted to investigations on nanomechanical behaviors of biochips in label-free biodetections. The chip consists of Si-layer, Ti-layer, Au-layer and single-strand DNA （ssDNA） molecular brush biolayer immobilized by self-assembly technology of thiol group. Unlike previous viewpoints, such as force-bending, entropy-bending and curvature electricity effect, etc., the piezoelectric effect of the biopolymer brush layer is viewed as the main factor that induces nanomechanical bending of biochips, and a classical macroscopic piezoelectric constitutive relation is used to describe the piezoelectric effect. A new laminated cantilever beam model with a piezoelectric biolayer in continuum mechanics, the linearized Poisson-Boltzmann equation in statistical mechanics and the scaling method in polyelectrolyte brush theory are combined to es- tablish a relationship between the nanomechanical deflection of DNA chips and the factors such as nanoscopic structural features of ssDNA molecules, buffer salt concentration, macroscopic mechanical/piezoelectric parameters of DNA chips etc. Curve fitting of experimental data shows that the sign of the piezoelectric constant of the biolayer may control the deflection direction of DNA chips during the packaging process.

Collapse of Four-Arm Stars Polyelectrolyte Brushes Under An Electric Field in the Presence of Trivalent Salt Coions

Langevin dynamics simulations were conducted to study the collapse of grafted partially charged 4-arm star chains onto the oppositely charged grafting electrode in the presence of trivalent salt coions.Simulation results reveal that the average charge fraction of the grafted star chains and the salt concentration play critical roles in the competitive adsorption of charged monomers and trivalent salt coions onto the oppositely charged electrode.For grafted star chains with relatively high charge fraction,charged monomers are the dominant species collapsing on the oppositely charged electrode with the emergence of charge reversal on the grafting electrode.At a low charge fraction such that the total amount of charges on a grafted star molecule is comparable to that of a trivalent salt coion,trivalent salt coions absorb more strongly onto the electrode than grafted stars even at very low salt concentration.It is found that at relatively low charge fraction of star chains,the addition of trivalent salt coions does not lead to charge overcompensation of the surface charges on the grafting electrode.The stretching of star brushes under an electric field in the presence of trivalent salt coions was also briefly investigated.

水基钻井液用抗超高温聚合物刷润滑剂的研制

深部复杂地层油气钻探过程中,为了满足钻井液抗高温、抗盐的技术要求,以甲基丙烯酸甲酯、丙烯酸月桂酯、丙烯酸羟乙酯为主要原料,偶氮二异丁腈作为引发剂,制备了一种水基钻井液用聚合物刷润滑剂HLM。通过傅里叶红外光谱、核磁共振、热重分析和凝胶色谱分析对产物进行了表征。然后评价了HLM与钻井液的配伍性以及高温、高盐、高密度条件下的润滑性能,利用多功能材料表面性能测试仪和四球摩擦实验仪进一步分析了润滑性。实验结果表明,HLM的热稳定性较好,重均分子质量为3494;HLM在室温下与基浆配伍性良好,对流变性基本没影响,抗温可达260℃;加量2%时,常温下润滑系数降低率达91.16%,260℃老化后润滑系数降低率达88.24%;在饱和盐水基浆中润滑系数降低率为75.69%,在高密度基浆中润滑系数降低率大于40%。表面摩擦实验进一步证明了HLM可以大幅度降低金属-金属间的摩擦力,四球摩擦实验证明了HLM可在金属表面形成稳定的润滑膜。由于HLM具有多个吸附位点且吸附能力强,在高温、高盐条件下吸附膜仍具有一定的强度,因此赋予HLM良好的润滑性能。可为深层超深层钻井液体系的构建提供技术借鉴。

超滑氟硅涂层研究进展

超滑氟硅涂层是一种新型的表面功能涂层,因其表面具有类似液体和分子光滑的特性而表现出良好的疏液、自愈合、防结冰、防指纹、防生物污损等性能,具有重要应用前景。本文介绍了超滑液体浸润涂层(或表面)和类液态高分子刷涂层2类超滑涂层的制备原理和性能特点。其中,前者通过超滑液体浸润多孔基底或溶胀于涂层基体之中获得,该涂层(或表面)润滑性强、自修复效果好,但易受侵蚀;后者通过氟硅高分子刷化学键合于基材表面或整个涂层基体之中制得,超滑性能相对较弱,但机械稳定性较好。进一步,重点介绍了2类超滑涂层的性能提升策略及已取得的进展。最后,指出了超滑涂层未来发展所面临的挑战。

平行场刷形等离子体羽的放电特性及其聚合物表面改性

大气压等离子体射流可以在开放空间产生富含活性粒子的等离子体羽,在材料生长、表面改性、生物医疗等领域具有广泛的应用前景.由于通常等离子体羽的截面尺度很小,造成等离子体射流应用时效率较低,因此,急需产生大尺度的等离子体羽.目前报道的大尺度的等离子体羽多是交叉场等离子体羽,相比于平行场等离子体羽而言其化学活性较低.针对于此,本文利用双电极结构的平行场氩气射流,通过交流激励产生了大尺度的刷形等离子体羽.利用电学、光学和光谱学手段对刷形等离子体羽的放电特性进行了表征.在此基础上,利用该平行场刷形等离子体羽对聚合物(聚对苯二甲酸乙二醇酯(PET))进行了改性研究.通过研究PET表面的水接触角(WCA)、拉曼光谱、X线光电子能谱(XPS)和原子力显微镜(AFM)照片,发现刷形等离子体羽能实现PET表面的大尺度均匀改性.改性后的PET表面含氧极性官能团数量显著增加,并且PET表面的粗糙度增加,因此亲水性得到改善,此种亲水性改良对不同的聚合物具有普适性.这些研究结果对于大尺度等离子体射流的深入研究及等离子体表面改性的应用均具有一定参考价值.