DNA translocation through polyelectrolyte‐modified nanopores: An analytical approximation

An analytical model for the electrophoretic speed of DNA translocating through nanopore functionalized with polyelectrolyte (PE) brush is developed for the first time. The electrophoretic speed depends on DNA surface potential, applied electric field, viscosity, and permittivity of solution along with velocity and electrostatic potential at liquid–polyelectrolyte layer (PEL) interface where the interface seemed to behave similar to that of a solid‐state nanopore wall. Under the limit of Debye–Hückel linearization, the electrostatic potential at liquid–PEL interface and at DNA surface have been calculated. Velocity at liquid–PEL interface has been estimated by assuming a linear variation of hydrodynamic frictional force within the PEL. It is observed that velocity and electrostatic potential at liquid–PEL interface strongly depend on PE charge density and softness parameter. Present analytical results show excellent agreement with exact numerical results (i.e., without any approximation) at a higher salt concentration where Debye–Hückel linearization is applicable.     

Preparation of Langmuir/Blodgett-cellulose Surfaces by Using Horizontal Dipping Procedure. Application for Polyelectrolyte Adsorption Studies Performed with QCM-D

A method of preparing model cellulose surfaces by the Langmuir–Blodgett (LB) technique with horizontal dipping procedure has been developed. The primary aim for the use of these surfaces was adsorption studies performed with the quartz crystal microbalance with dissipation (QCM-D) instrument. Hydrophobised cellulose (trimethylsilyl cellulose, TMSC) was deposited on the hydrophobic, polystyrene-coated QCM-D crystal. After 15 dipping cycles, the TMSC film fully covers the crystal surface. TMSC can easily be hydrolysed back to cellulose with acid hydrolysis. With this method a smooth, rigid, thin and reproducible cellulose film was obtained. Its morphology, coverage, chemical composition and wetting was further characterised using atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), and contact angle measurements. The swelling behaviour and the stability of the cellulose film in aqueous solutions at different ionic strengths were studied using the QCM-D instrument. The swelling/deswelling properties of the cellulose film were those expected of polyelectrolytes with low charge density; some swelling occurred in pure water and the swelling decreased when the ionic strength was increased. No significant layer softening was detected during the swelling. The effect of electrolyte concentration and polymer charge density on the adsorption of cationic polyelectrolytes on the cellulose surface was also investigated. At low electrolyte concentration less of the highly charged PDADMAC was adsorbed as compared to low charged C-PAM. The adsorbed amount of PDADMAC increased with increasing ionic strength and a more compact layer was formed while the effect of electrolyte concentration on the adsorption of C-PAM was not as pronounced.     

Polyelectrolyte brushes

We survey recent progress made in the field of polyelectrolyte brushes. These systems consist of long polyelectrolyte chains that are grafted densely to planar or curved surfaces. The main feature of all polyelectrolyte brushes is the strong confinement of the counterions within the brush layer. The high osmotic pressure which is thus built up explains the unusual features of these systems. Here we focus on the most recent experimental developments which are rationalized on the basis of existing theoretical predictions and opens new challenging problems. In particular, we shall discuss briefly the experimental systems used for comparing theory and experiment lately. Moreover, we review various aspects related to the experimental analysis of polyelectrolyte brushes. As a final point, we survey trends in recent applications which demonstrate that polyelectrolyte brushes have an excellent prospect for future nanotechnology.     

旋涂-逐层自组装制备光响应性聚丙烯酸酯类偶氮聚电解质多层膜

偶氮聚电解质的静电逐层自组装是实现偶氮聚合物功能性的重要手段,是制备诸如光存储材料、光开关材料和非线性光学材料等的新途径.因此,光响应性偶氮聚电解质的静电逐层自组装已引起了人们的广泛关注.静电逐层自组装通常在水溶液中进行,即通过基材在在水溶液中的交替浸渍和逐层     

Mass transfer of a neutral solute in polyelectrolyte grafted soft nanochannel with porous wall

A soft nanochannel involves a soft interface that contains a polyelectrolyte layer (PEL) sandwiched between a rigid surface and a bulk electrolyte solution. Mass transfer of a neutral solute in a combined electroosmotic and pressure driven flow through a polyelectrolyte grafted charged nanochannel with porous wall is presented in this work. Assuming the PEL as fixed charged layer and PEL-electrolyte interface as a semi-penetrable membrane, analytical solutions were obtained for potential distributions (for small wall potential). Velocity profiles were also derived in the same domains, for both inside and outside the PEL. Convective-diffusive species balance equation was semi-analytically solved inside the PEL. Expression of length averaged Sherwood number was also obtained and effects of different parameters, namely, drag parameter (α), Debye parameter , and PEL thickness were studied in detail. The variation of permeate concentration and permeation flux across the porous wall was obtained.     

A NEW TYPE LOW SHEAR RATE VISCOMETER FOR HIGH MOLECULAR WEIGHT POLYMER

In this paper, the effects of shear rate on the intrinsic viscosity measurement of partiallyHydrolysed Polyacrylamide (HPAM) in salt solution were studied with homemade multi-bulb viscometer and low shear rate rheometer. The critical shear rate of HPAM in saltsolution for high molecular weight HPAM was determined. A low shear rate capillaryviscometer was designed in which the [η] approached to value at zero shear rate can beobtained for HPAM-salt system. The effect of molecular weight on shear rate dependenceof viscosity was also studied.     

离子型芘衍生物同聚电解质键合平衡的模拟

利用平衡键合模型模拟了聚电解质同荧光探针离子键合过程的计量关系 ,以及添加盐竞争键合时的计量关系 .计算的结果能够描述荧光实验结果 .芘离子探针PyMeA·HCl的IE IM 随着探针浓度的增加 ,会出现一个极大值 ,此极大值能够定量地给出饱和键合计量关系 .当盐浓度和聚电解质荷电单元浓度相当时 ,盐离子和芘离子探针发生明显的竞争键合 ,部分离子探针被排挤入水相 ,实验的IE IM 随盐浓度增大急剧减小     

Polymerlzatlon of 1-Ethynyl-1-Cyclohexanol by Radiation,Electroinitiation, and Chemical Catalysts

Abstract

Solid-state polymerization of 1-ethynyl-1-cyclohexanol was carried out by irradiation in vacuum and in open air at 20°C. Radiation-induced polymerization was also done in a benzene solution. The products were mixtures of oligomers and polymers. IR, NMR, U V, and x-ray investigations showed the initial formation of trimer, oligomer, and polymer. The polymer fraction increased with an increase of conversion. Electro-initiated polymerization gave soluble and insoluble fractions. The soluble fraction was an ether. However, the results were not reproducible. No polymers were obtained with n-butyllithium and borontrifluoride etherate as chemical catalysts.     

Stimuli-responsive polymer/metal composites: From fundamental research to self-regulating devices

The review focuses on stimuli–responsive composite materials consisting of polymers and metals. Special attention is drawn to the conversion of one external stimulus into another one, which leads to a cascade effect on the interaction with the vicinity. Beside fundamental aspects concepts for technical applications of those polymer/metal composites are presented.     

聚电解质渗透汽化膜

介绍了聚电解质渗透汽化膜的研究进展，包括聚电解质以及聚电解质复合物的定义、特点、制备、着重介绍了近年来开发的一些重要的聚电解质渗透汽化膜的制备方法及其分离性能。