STUDIES ON RELATION BETWEEN INTRINSIC VISCOSITY OF POLYELECTROLYTES IN SOLUTIONS USED FOR LAYER-BY-LAYER SELFASSEMBLY AND THEIR CORRESPONDING ADSORPTION AMOUNTS IN THE RESULTANT MULTILAYER MEMBRANES

The adsorption amount of poly(styrene sulfonate) and poly(dimethyldiallyl ammonium chloride) (PSS/PDDA) self-assembled multilayer membranes in designed dipping solvents were measured by UV-Vis-spectroscopy and quartz crystal microbalance (QCM). Intrinsic viscosities of PSS and PDDA in corresponding dipping solvents were determined by an Ubbelohde viscometer. It is found that the adsorption amount of PSS/PDDA self-assembled multilayer membranes built up in different dipping solutions, added salt concentration, pH of solution and solvent quality, respectively changed oppositely with the corresponding intrinsic viscosity of PSS and PDDA in dipping solvents. A negative relation between the adsorption amount and intrinsic viscosity was revealed, and explained in term of the concept of excluded volume of polymer molecule in dilute solutions.

Self-Assembly of <i>Escherichia coli</i>Phage Shock Protein A

The Phage shock protein (Psp) response is an extracytoplasmic stress response. The central component of this system is PspA, a protein that mediates the physiological response to membrane stress. PspA is also involved in regulating its own transcription and that of the psp operon, forming a positive feedback loop. PspA has been previously shown to oligomerise into higher-order species, including a 36-meric species with ring-like structure. In this study, we demonstrate that the ring-like PspA structures further self-assemble into rod-shaped complexes. These rod-like structures may play a scaffolding role in the maintenance of membrane integrity during phage shock protein response.

Do membrane proteins cluster without binding between molecules?

Clustering is a basic event for the initiation of immune cell responses, and simulation analyses of clustering of membrane proteins have been performed. It was claimed that a cluster is formed by the self-assembly induced by protein dimerization with a high binding speed (Woolf and Linderman, Biophys. Chem. 104, 217-227, 2003). We examined the cluster formation with Monte Carlo simulation using two algorithms. The first was that simulation processes were divided into two substeps. All proteins were subjected to movement in the first substep, followed by reaction in the second substep. The second algorithm was that proteins were first selected to react and proteins which did not react were subjected to movement. The self-assembly induced by dimerization was simulated only with the second algorithm. In this algorithm, monomers dissociated from dimers do not move because these monomers are not selected for movement, and a large proportion of such monomers are selected to form dimers in the next step. The self-assembly was again simulated with the first algorithm containing the conditions that monomers dissociated from dimers did not move in the next movement substep. This algorithm seems to be far removed from natural conditions. Thus, it is inferred that the self-assembly induced by dimerization is unlikely in situ, and that some interaction between proteins is required for cluster formation. In contrast to algorithms in previous simulations, our results suggest that it is more appropriate that proteins move to the same direction for a while and reflect when the collision occurs.

接枝改性SAMS-CMC-CS双极膜及在电合成高铁酸盐中的应用

采用双阴极室隔膜电解槽,以SAMS-CMC-CS双极膜为隔膜,多孔圆筒铸铁为阳极,结合变频不对称脉冲方波技术电合成高铁酸盐。扫描电镜观察,膜的截面形貌。FT-IR分析表明膜中含有-SO3-、-COO-、-N=CHR官能团。膜特性研究表明:该膜溶胀度较小,可有效地阻止FeO42-向阴极室扩散还原。双极膜中的水解离后产生的OH-及时地传输入阳极室中,以补充电生成FeO42-时消耗的OH-。电解6h,平均电流效率64.1%。

Toward the Highly Ordered Lamellar Hybrid Membrane for Molecular Sieving by One-Pot Self-Assembly of Hybrid Hyperbranched Polymer

Ordered lamellar hybrid membranes are of great interest,due to their application as functional materials,including molecular sieving,biosensors,optical devices,and drug,as well as gene deliveries,but their fabrication remains challenging because three critical issues regarding synthesis of regular nanosheets,interfacing,and their spatial distribution in a polymer matrix are difficult to address simultaneously.Here,we fabricated a well-defined hybrid lamellar membrane through one-pot self-assembly,whose structure consisted of alternating layers of hydrophilic hyperbranched poly(ether amine)(hPEA)and polyhedral oligomeric silsesquioxane(POSS).

Studies of Self-assembled Monolayers Formed by Imidazofine on Iron Surface by SEM and SECM

The self-assembled monolayers （SAMs） of imidazoline （IM） on the iron surface were characterized by scanning electron microscope （SEM） and scanning electrochemical microscopy （SECM）. The results showed that SAMs were an effective inhibition film for iron.

In situ crosslinking of polyoxometalate-polymer nanocomposites for robust high-temperature proton exchange membranes

The most practical high-temperature proton exchange membranes(PEMs) are phosphoric acid(PA)-doped polymer electrolytes. However, due to the plasticizing effect of PA, it is a challenge to address the trade-off between the proton conductivity and the mechanical performance of these materials. Here,we report an effective strategy to fabricate robust high-temperature PEMs based on the in situ electrostatic crosslinking of polyoxometalates and polymers. A comb copolymer poly(ether-ether-ketone)-grafted-poly(2-ethyl-2-oxazoline)(PGE) with transformable side chains was synthesized and complexed with H_(3)PW_(12)O_(40)(PW) by electrostatic self-assembly, forming PGE/PW nanocomposite membranes with bicontinuous nanostructures. After a subsequent PA-treatment of these membranes, high-temperature PEMs of PGE/PW/PA ternary nanocomposites were obtained, in which the in situ electrostatic crosslinking effect between PW and PGE side chains was generated in the hydrophilic domains of the bicontinuous structures. The microphase separation structure and the electrostatic crosslinking feature endow the PGE/PW/PA membranes with excellent anhydrous proton conductive ability while retaining high mechanical performance. The membranes show a high proton conductivity of 42.5 m S/cm at 150 ℃ and a high tensile strength of 13 MPa. Our strategy can pave a new route based on electrostatic control to design nanostructured polymer electrolytes.

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

Layer-by-layer assembly is a versatile technique for fabricating nanofiltration membranes,where multiple layers of polyelectrolytes are usually required to achieve reasonable separation performance.In this work,an ionic strength directed self-assembly procedure is described for the preparation of nanofiltration membranes consisting of only a single bilayer of poly(diallyldimethylammoniumchloride)and poly(sodium-4-styrenesulfoate).The influence of background ionic strength as well as membrane substrate properties on the formation of singlebilayer membranes are systematically evaluated.Such a simplified polyelectrolyte deposition procedure results in membranes having outstanding separation performance with permeating flux of 14.21.5 L∙m^(–2)∙h^(-1)∙bar^(–1) and Na2SO4 rejection of 97.1%0.8%under a low applied pressure of 1 bar.These results surpass the ones for conventional multilayered polyelectrolyte membranes.This work encompasses an investigation of ionic strength induced coiling of the polyelectrolyte chains and emphasizes the interplay between-polyelectrolyte chain configuration and substrate pore profile.It thus introduces a new concept on the control of membrane fabrication process toward high performance nanofiltration.

分子自组装技术在防银表面变色中的研究与应用前景

银工艺饰品很容易变色。针对电镀贵金属、化学钝化、电化学钝化、保护性配合物膜、固体润滑层、高分子涂料等常用的几类防银变色表面处理方式存在的不足,介绍了分子自组装成膜的原理和特点,及其在防银变色方面的研究情况和应用效果,并分析了分子自组装膜在防银工艺饰品变色方面的广阔应用前景和需要进一步研究的一些问题。

铝表面自组装端羟基聚酯胺膜的XPS和STM表征

制备了端羟基聚酯胺(HTP)在铝基片上的自组装膜并进行了XPS和STM表征,确认了HTP在铝基片上的吸附组装;由XPS的吸附时间扫描,自组装单分子膜(SAMs)随浸泡时间的延长而增厚,在2 h后达到平衡。由HTP在铝基片的STM三维图可以看到HTP自组装膜以团块形式组成,其间包含孔洞缺陷。提出了铝基片上HTP–SAMs的多羟基结构与膜上孔洞的共同作用是提高环氧类涂层附着力的主要原因。

Facilely prepared layer-by-layer graphene membrane-based pressure sensor with high sensitivity and stability for smart wearable devices

With the prosperous development of artificial intelligence,medical diagnosis and electronic skins,wearable electronic devices have drawn much attention in our daily life.Flexible pressure sensors based on carbon materials with ultrahigh sensitivity,especially in a large pressure range regime are highly required in wearable applications.In this work,graphene membrane with a layer-by-layer structure has been successfully fabricated via a facile self-assembly and air-drying(SAAD)method.In the SAAD process,air-drying the self-assembled graphene hydrogels contributes to the uniform and compact layer structure in the obtained membranes.Owing to the excellent mechanical and electrical properties of graphene,the pressure sensor constructed by several layers of membranes exhibits high sensitivity(52.36 kPa……-1)and repeatability(short response and recovery time)in the loading pressure range of 0–50 kPa.Compared with most reported graphene-related pressure sensors,our device shows better sensitivity and wider applied pressure range.What’s more,we demonstrate it shows desired results in wearable applications for pulse monitoring,breathing detection as well as different intense motion recording such as walk,run and squat.It’s hoped that the facilely prepared layer-by-layer graphene membrane-based pressure sensors will have more potential to be used for smart wearable devices in the future.

Molecular Dynamics Study of Dipalmitoylphosphatidylcholine Lipid Layer Self-Assembly onto a Single-Walled Carbon Nanotube

Single-walled carbon nanotubes(SWNTs)are possible nano-injectors and delivery vehicles of molecular probes and drugs into cells.In order to explore the interaction between lipid membranes and carbon nanotubes,we investigate the binding mechanism of dipalmitoylphosphatidylcholine(DPPC)with SWNTs by molecular dynamics.In low concentration range simulations,the DPPC molecules form a supramolecular two-layered cylindrical structure wrapped around the carbon nanotube surface.The hydrophobic part of DPPC is adsorbed on the surface of the nanotube,and the hydrophilic top is oriented towards the aqueous phase.For higher concentration ranges,the DPPC molecules are found to form a supramolecular multi-layered structure wrapped around the carbon nanotube surface.At the saturation point a membrane-like structure is self-assembled with a width of 41.4Å,which is slightly larger than the width of a cell membrane.Our study sheds light on the existing confl icting simulation data on adsorption of single-chained phospholipids.

金属表面绿色环保自组装防腐膜的研究进展

自组装膜技术在金属表面防腐中的应用越来越广泛,采用简单有效的膜技术制备绿色环保膜产品已成为防腐 膜领域的研究热点。本文综述近年来金属表面自组装膜制备技术的研究进展,分别阐述了金属表面自组装单层膜 和复合膜在铝/铝合金、铜/铜合金、不锈钢和其他活泼金属表面自组装膜技术的分类、特点和应用、防腐机理等,指 出膜与基体之间的界面结合、成膜机理、防腐机理等方面的研究还不够完善,仍然是亟待解决的科学问题。

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing Trans/Cis Isomers

Nanoporous membranes and vesicles are interesting systems with potential in applications offering channels for material exchange.Herein,nanoporous membranes and polymersomes are developed by self-assembly of trans-and cis-stereoisomers of amphiphilic polymers.Two polymers,PEG550-TPEChol and PEG550-SS-TPE-SS-Chol,containing a central tetraphenylethene(TPE),a cholesterol(Chol),and a poly(ethylene glycol)(PEG550)are studied.

Rapidly SO2-responsive vesicles with intrinsic fluorescent indicators for membrane structure evolution

Stimuli-responsive vesicles(SRVs)have been widely exploited as smart nanocarriers for biomedical applications.Herein,high-performance SO2-responsive nanovesicles were reported to exemplify a new mode of SRVs.Structurally,the sensory vesicles were based on amphiphilic hydrogen-bonded(HB)polymers which can be facilely fabricated via modular self-assembly.The HB polymers are designed to consist of a melamine-barbituric acid HB skeleton with pendant anthracene fluorophores and amphiphilic side chains.Upon stimulation with increasing amount of SO2,the vesicles in aqueous solution undergo an unusual morphology evolution including rapid fission into small ones,swelling and final collapse of the offspring vesicles.During this process,the intrinsic fluorescence response of the vesicles allows intuitive tracking of the hierarchical structural evolution of the self-assembled membranes and straightforward quantitation of the stimuli.This work exemplifies a rational design of auto-recording stimuli-responsive nanovesicles.

Pearling and helical nanostructures of model protocell membranes

The diversity of protocell membrane structures is crucial for the regulation of cell activities and indispensable to the origin of life.Prior to the evolution of complex cellular machinery,spontaneous protocell membrane evolution results from the intrinsic physicochemical properties of simple molecules under specific environmental conditions.Here,we report the evolution of the morphology of cell-sized model protocell membranes from giant vesicles to pearling and helical nanostructures,resembling morphologies of eukaryocytes,nostoc,and spirilla.This evolution occurs in a single binary aqueous system composed of an achiral single-chain amphiphile and a biogenic polyamine(spermidine or spermine)upon evaporating water,feeding amphiphiles,or increasing pH in response to various primitive fluctuating conditions.In contrast,nonbiogenic polyamines(triamine,triethylenetetramine,and hexamethyltriethylenetetramine)with slight differences in the number of methylene groups or protonated amine groups do not induce such a kind of evolution.The evolution of the shape transformation strongly relies on the balance between electrostatic attraction and hydrogen bonding,attributed to the odd/even effect of polyamines in the assembly.Strikingly,both pearling and helical structures emerge from multilamellar vesicles undergoing different processes,where the helix shows stronger permeability and encapsulation capability due to its multicompartmentalized structure.Thus,subtle adjustment of weak intramolecular interactions not only yields significant changes in the morphological evolution of protocell membranes but also brings new insights into the natural inevitability of biogenic small molecules.

Superwetting polyethersulfone membrane functionalized with ZrO_(2) nanoparticles for polycyclic aromatic hydrocarbon removal

Polycyclic aromatic hydrocarbons(PAHs)are persistent and widespread in the aquatic environment,causing potential hazards for human health.In this study,a superwetting and robust PES-PAA-ZrO_(2)nanofiltration membrane was proposed through surface modification for PAH removal with high efficiency.A ZrO_(2)coating was formed on polyethersulfone(PES)membrane surface through chemical bonding,thus the PES-PAA-ZrO_(2)membrane exhibited super-hydrophilicity,under-water oleophobicity,and excellent stability.In comparison with the original PES membrane,the water contact angle of the modified membrane was significantly decreased from about 50°to less than 10°,and quickly dropped to 0°within 1s.This provided a much lower energy barrier for water permeation due to its super-high water affinity.The wastewater treatment efficiency was increased by about 4 times after modification with more than 90%of PAH rejection rate.The excellent robustness of PES-PAA-ZrO_(2)membrane was verified under various conditions,which gave the membrane practical potential for long-term operation.

Lateral dipole moments induced by all-cis-pentafluorocyclohexyl groups cause unanticipated effects in self-assembled monolayers

All-cis-hexafluoro-and all-cis-pentafluoro-cyclohexane(PFCH)derivatives are new kinds of materials,the structures and properties of which are dominated by the highly dipolar Janus-face motif.Here,we report on the effects of integrating the PFCH groups into self-assembled monolayers(SAMs)of alkanethiolates on Au(111).Monolayers with an odd(eleven)and even(twelve)number of methylene groups were characterized in detail by several complementary experimental tools,supported by theoretical calculations.Surprisingly,all the data show a high similarity of both kinds of monolayers,nearly lacking the typically observed odd-even effects.These new monolayers have a packing density about 1/3 lower than that of non-substituted alkanethiolate monolayers,caused by the bulkiness of the PFCH moieties.The orientations of the PFCH groups and the alkyl chains could be determined independently,suggesting a conformation similar to the one found in the solid state structure of an analogous compound.Although in the SAMs the PFCH groups are slightly tilted away from the surface normal with the axial fluorine atoms pointing downwards,most of the dipole moments of the group remain oriented parallel to the surface,which is a unique feature for a SAM system.The consequences are much lower water contact angles compared to other partly fluorinated SAMs as well as rather moderate work function values.The interaction between the terminal PFCH moieties results in an enhanced stability of the PFCH-decorated SAMs toward exchange reaction with potential molecular substituents in spite of the lower packing density of these films.

A Comparison Study on Corrosion Resistance of 430 Stainless Steel Surfaces Modified by Alkylsilane and Fluoroalkylsilane SAMs

The self-assembly monolayers （SAMs） of n-dodecyltriethoxysilane （DTES） and 1 H, 1 H, 2H, 2H-perflu- orodecyltriethoxysilane （PFDS） on the surface of the 430 stainless steel （430SS） were prepared and their corrosion protection performance was investigated by potentiodynamic polarization, Fourier transform infrared spectroscopy （FTIR） -attenuated total reflection （ATR）, static contact angle and atomic force microscopy （AFM）. The results showed that the alkali pretreatment and the water added into the self-assembly solution could generate more hydrox- yls on the 430SS surface, and then enhanced the adsorption of the SAMs. A suitable temperature of the self-assem- bly solution is important for the formation of the SAMs. The silane SAMs were chemically adsorbed on the 430SS substrates by Fe-O-Si bonds. In all cases tested, PFDS has a better inhibition effect compared with DTES, and the difference in inhibition effect is most marked at the lowest concentration of 1 mmol/L.