两嵌段共聚高分子在固液界面吸附的Monte Carlo模拟(Ⅰ)——吸附链的构型分布

用MonteCarlo方法对两嵌段共聚高分子在固液界面的吸附进行模拟,获得了固液界面区吸附链节的分布和吸附构型大小分布等微观信息.考察了吸附性链节的吸附能ε_Aa和两嵌段共聚高分子中吸附性链节比例f对固液界面区高分子链节的分布和各种吸附构型大小的影响.结果表明,吸附层厚度主要由两嵌段共聚高分子中非吸附性链段的长度决定.     

石英晶体微天平在高分子科学中的应用

固/液界面上高分子的行为直接影响着界面的物理和化学性质.对于高分子在界面的动态行为,由于缺乏有效的手段,检测一直十分困难.最近,一种频率-耗散联用型石英晶体微天平(QCM-D)问世,它能够同时检测固/液界面上有关高分子质量和结构的变化,因而可应用于界面高分子研究的多个方面.本文介绍石英晶体微天平的基本原理,并综述作者实验室最近几年利用QCM-D开展的若干工作,包括固/液界面上高分子链的构象变化,固/液界面上高分子的吸附,高分子降解动力学和聚电解质的"层层组装"等方面.     

隐藏高分子界面及生物界面分子结构的和频振动光谱研究

界面的分子结构决定界面的性质.为了以优化界面的结构来改进材料的性质,原位实时地研究界面的分子结构是很重要的.近年来和频振动光谱已发展成为一个很有效及独特的手段来研究隐藏界面的分子结构,例如液/液界面、固/液界面及固/固界面等.这篇综述讨论了和频振动光谱在研究高分子界面及生物界面等复杂界面的分子结构上的应用.具体说来,本文论述了高分子表面在水里的分子结构变化,高分子及模型粘合促进剂硅烷在界面相互作用的分子机理和隐藏的高分子/高分子及高分子/金属界面的结构.另外,此文还将介绍不同二级结构的多肽及几个有代表性的蛋白分子在界面的结构.界面在诸如化学、生物、物理、材料科学及工程和纳米技术等许多领域都很重要.发展一个独特的能原位研究隐藏界面的分子结构的技术会有力地促进这些领域的研究及跨学科研究的发展.     

两嵌段共聚高分子在固液界面吸附的Monte Carlo模拟（Ⅰ）— …

用Ｍｏｎｔｅ Ｃａｒｌｏ方法对两嵌段共聚高分子在固液界面的吸附进行模拟,获得了固液界面区吸附链节的分布和吸附构型大小分布等微观信息。考察了吸附性链节的吸附能εＡａ和两嵌段共聚高分子中吸附性链节比例ｆ对固液界面区高分子链节的分布和各种吸附构型大小的影响。结果表明,吸附层厚度主要由两嵌段共聚高分子中非吸附性链段的长度决定。     

放射性核素在固-液界面上的吸附：模型及其应用

放射性核素在固-液界面上的吸附行为是其在低浓度下物理化学行为研究的重要内容之一。本文综述了固-液界面吸附研究方面取得的主要进展,总结了放射性核素在固-液界面的吸附动力学、热力学模型,重点讨论了表面配位模型和亚稳态理论在固-液界面吸附行为研究中的应用和发展,较为详细地概括了部分先进光谱技术、理论计算方法和模型模拟手段等在...     

两嵌段共聚高分子在固液界面吸附的Monte Carlo模拟(Ⅱ)──界面浓度分布和吸附量

用MonteCarlo方法对两嵌段共聚高分子在固液界面的吸附进行模拟,获得了固液界面区总链节密度和吸附链节浓度分布、链附着率、表面覆盖率和吸附量等信息,考察了吸附性链节的对比吸附能 ε>_An 和两嵌段共聚高分子中吸附性链节比例f对它们的影响.结果表明,较大时,吸附量先随f的增加而上升,在f=0.4左右达到最大值后逐渐下降.     

水溶性高分子在固/液界面上吸附行为的光物理研究进展

本文概述了物理方法的特点,评述了水溶性高分子在固／液界面上吸附行为的光物理研究进展。     

两嵌段共聚高分子在固液界面吸附的MonteCarlo模型（Ⅱ）：？…

用ＭｏｎｔｅＣａｒｌｏ方法对两嵌段共聚高分子在固液界面的吸附进行模拟,获得了固液我总链节密度和吸附链节浓度分布、链附着率、表面覆盖率和吸附量等信息,考察了吸生链节的对比吸附能εＡａ和两嵌段共聚高分子中吸附性链节比例ｆ对它们的影响,结果表明,εＡａ在时吸附量先随ｆ的增加而上升,在ｆ＝０．４左右达到最大值后逐渐下降。     

高分子固液复合界面与液体黏附调控

受猪笼草口缘区润滑效应启发,将低表面能液体注入高分子微纳米多孔结构中可构筑高分子固液复合界面.与超疏水固体界面相比,固液复合界面展现出独特的浸润性和黏附性.界面黏附是高分子复合材料重要的性质之一,实现界面黏附的精准调控对促进这类材料的发展和应用具有至关重要的作用.本文重点从稳定性调控、方向性调控以及原位可逆调控3个方面综述提升固液复合界面黏附可控性的工作,通过在表面微米结构中组装纳米层状及异质纳米层状结构,提高界面黏附的稳定性;使用界面薄层定向冷冻干燥法、激光刻蚀法以及复型法等方法,构筑具有取向结构的高分子固液复合界面,实现界面黏附的方向性调控;通过在界面中引入快速响应的智能基元,设计智能响应高分子固液复合界面,实现界面黏附的原位可逆调控.最后,概述了这类材料目前存在的问题并展望了其未来发展的方向.     

石英晶体微天平在高分子研究中的应用

石英晶体微天平(QCM)作为一种强有力的表征工具已被广泛应用于高分子研究之中.本文中,作者介绍了QCM的发展简史、基本原理以及实验样品制备方法 .在此基础上,介绍了如何基于带有耗散测量功能的石英晶体微天平(QCM-D)及相关联用技术研究界面接枝高分子构象行为、高分子的离子效应以及高分子海洋防污材料,展示了QCM-D技术在高分子研究中的广阔应用前景. QCM-D可同时检测界面高分子薄膜的质量变化和刚性变化,从而反映其结构变化.与光谱型椭偏仪联用后,还可同步获取界面高分子薄膜的厚度变化等信息,可以有效解决相关高分子研究中的问题.希望本文能够对如何利用QCM-D技术开展高分子研究起到一定的启示作用,使这一表征技术能够为高分子研究解决更多问题.     

A Review of Temperature Influence on Adsorption Mechanism and Conformation of Water Soluble Polymers on the Solid Surface

The temperature effect on adsorption behavior of water soluble polymer and structure of its adsorption layer formed on the solid surface is presented. The main reasons for such problem explanation are wide application possibilities of stabilization-flocculation properties of polymers in many technological and ecological processes and very poor knowledge about temperature dependences of high-molecular compounds adsorption on the solid surface. To systematize the information about the effect of temperature on polymer chain conformation on the adsorbent surface the following aspects were considered: thermodynamic and physicochemical characteristics of polymer solutions, stabilization-flocculation properties of polymers in the dispersed systems, and presentation of respective experimental results. The theoretical and experimental evidence of the temperature effect on polymer macromolecule conformation on the solid surface presented in the article can contribute to better knowledge and understanding of the adsorption process at the metal oxide-polymer solution interface in the temperature function.     

Molecular simulation of protein adsorption and conformation at gas-liquid,liquid–liquid and solid–liquid interfaces

The adsorption of proteins at surfaces and interfaces is important in a wide range of industries. Understanding and controlling the conformation of adsorbed proteins at surfaces is critical to stability and function in many technological applications including foods and biomedical testing kits or sensors. Studying adsorbed protein conformation is difficult experimentally and so over the past few decades researchers have turned to computer simulation methods to give information at the atomic level on this important area. In this review we summarize some of the significant simulation work over the past four years at both fluid (liquid–liquid and gas–liquid interfaces) and solid–liquid interfaces. Of particular significance is the work on surfactant proteins such as fungal hydrophobins, ranspumin-2 from the túngara frog and the bacteria protein BslA. These have evolved unique structures impart very high surface-active properties to the molecules. A highlight is the elucidation of the clam-shell unhinging mechanism of ranspumin-2 adsorption to the gas–liquid interface that is responsible for its adsorption to and stabilization of the air bubbles in túngara frog foam nests.     

Facile preparation of polydopamine‐coated imprinted polymers on the surface of SiO2 for estrone capture in milk samples

Estrone molecularly imprinted polymers were synthesized through the self‐polymerization of dopamine on the surface of silica gels, which had the characteristics of mild polymerization conditions, simple reaction procedure and good specific recognition ability for estrone. The estrone molecularly imprinted polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and nitrogen adsorption–desorption tests. The characterization confirmed that the imprinted polymers were successfully grafted on the surface of silica gels. Through investigating the adsorption performance, the prepared estrone molecularly imprinted polymers exhibited high adsorption capacity, fast mass transfer, as well as excellent selectivity toward estrone. The estrone molecularly imprinted polymers as the solid‐phase extraction adsorbent coupled with high‐performance liquid chromatography was developed to determine estrone from the milk samples. The developed estrone molecularly imprinted polymer solid‐phase extraction with high‐performance liquid chromatography method exhibited satisfactory specificity, precision, accuracy and good linearity relationship in the range of 0.2–20 μg/mL. The developed method is simple, fast, effective and high specificity method and it provides a new method to detect the residues of estrone in animal foods.     

Dynamic behavior of flexible polymers at a solid/liquid interface

The mean time spent by a macromolecule at a solid/liquid interface is analyzed in the region of adsorption saturation. The method consists of carrying out preliminary adsorption with radioactively labeled high-molecular-weight polyacrylamide and subsequently exposing the surface to a solution of unlabeled polyacrylamide. It was found that, apart from a small fraction of polymers “loosely” attached, the exchange between labeled and unlabeled polymers takes place at the interface at a very slow rate. Furthermore, desorption of surface molecules occurs only in the presence of a solution, and then the rate of desorption increases proportionally to the number of molecules in the solution. A mechanism based on a bimolecular chemical exchange process is proposed.     

Potential-modulation spectroscopy at solid/liquid and liquid/liquid interfaces.

Potential-modulation spectroelectrochemical methods at solid/liquid and liquid/liquid interfaces are reviewed. After a brief summary of the basic features and advantages of the methods, practical applications of potential-modulation spectroscopy are demonstrated using our recent studies of solid/liquid and liquid/liquid interfaces, including reflection measurements for a redox protein on a modified gold electrode and fluorescence measurements for various dyes at a polarized water/1,2-dichloroethane interface. For both interfaces, the use of linearly polarized incident light enabled an estimation of the molecular orientation. The use of a potential-modulated transmission-absorption measurement for an optically transparent electrode with immobilized metal nanoparticles is also described. The ability of potential-modulated fluorescence spectroscopy to clearly elucidate the charge transfer and adsorption mechanisms at liquid/liquid interfaces is highlighted.     

Site blocking effect on the conformation of adsorbed cationic polyacrylamide on a solid surface

It has been known that pre-adsorbed polymers on a solid surface can block some adsorption sites for a post-added polymer on the same substrate. If the charge of pre-adsorbed polymer is the same as that of post-adsorbed polymer, the repulsion force between these two polymers will change not only the polymer adsorption amount but also the conformation and the properties of the polymer on the substrate. The site blocking effect is a possible mechanism in many commonly used flocculation programs. However, no research has been able to confirm the proposed theory of its effects on adsorbed polymer conformation. This work reports, for the first time, detailed information regarding the effects of site blocking on an adsorbed polymer's conformation using scanning probe microscopy. Using both polymers and nanoparticles as site blocking additives, experiments were performed on single cationic polyacrylamide polymers. This work illustrates that the increased thickness in adsorbed polymer layers, reported by previous researchers, is due to a dramatic increase in the tail portion of the adsorbed polymer. The previously postulated increase in adsorbed polymer loop lengths was not present in these experiments.     

Innovative method for the enrichment of high‐polarity bioactive molecules present at low concentrations in complex matrices

Ginsenoside Rg1 is a valuable bioactive molecule but its high polarity and low concentration in complex mixtures makes it a challenge to separate Ginsenoside Rg1 from other saponins with similar structures, resulting in low extraction efficiency. The successful development of effective Rg1 molecularly imprinted polymers that exhibit high selectivity and adsorption may offer an improved method for the enrichment of active compounds. In this work, molecularly imprinted polymers were prepared with two different methods, precipitation polymerization or surface imprinted polymerization. Comparison of the adsorption abilities showed higher adsorption of the surface molecularly imprinted polymers prepared by surface imprinted polymerization, 46.80 mg/g, compared to the 27.74 mg/g observed for the molecularly imprinted polymers prepared by precipitation polymerization. Therefore, for higher adsorption of the highly polar Rg1, surface imprinted polymerization is a superior technique to make Rg1 molecularly imprinted polymers. The prepared surface molecularly imprinted polymers were tested as a solid‐phase extraction column to directionally enrich Rg1 and its analogues from ginseng tea and total ginseng extracts. The column with surface molecularly imprinted polymers showed higher enrichment efficiency and better selectivity than a C₁₈ solid‐phase extraction column. Overall, a new, innovative method was developed to efficiently enrich high‐polarity bioactive molecules present at low concentrations in complex matrices.     

Preparation and evaluation of a molecularly imprinted sol–gel material as the solid‐phase extraction adsorbents for the specific recognition of cloxacilloic acid in cloxacillin

Highly selective molecularly imprinted polymers on the surface of silica gels were prepared by a sol–gel process and used as solid‐phase extraction adsorbents for the specific recognition, enrichment and detection of cloxacilloic acid in cloxacillin. The obtained polymers were characterized by scanning electron microscopy, FTIR spectroscopy, nitrogen adsorption and desorption, elemental analysis and thermogravimetric analysis. The imprinted polymers not only possessed high adsorption capacity (6.5 μg/mg), but also exhibited fast adsorption kinetics (they adsorb 80% of the maximum amount within 20 min) and excellent selectivity (the imprinted factor was 3.6). A method using the imprinted polymers as solid‐phase extraction adsorbents coupled with high‐performance liquid chromatography was established with good specificity, linearity (r = 0.9962), precision (ranging from 0.5 to 6.7%), accuracy (ranging from 93.9 to 97.7%) and extraction recoveries (ranging from 78.8 to 89.8%). The limits of detection and quantification were 0.07 and 0.25 mg/g, respectively. This work could provide a promising method in the enrichment, extraction and detection of allergenic impurities in the manufacture, storage and application of cloxacillin.     

Probing the polymer anomalous dynamics at solid/liquid interfaces at the single-molecule level

A goal across multiple scientific fields (e.g. separations, polymer processing, and biomaterials) is to understand polymer dynamics at solid/liquid interfaces. In the last two decades, rapid developments in single-molecule techniques have revolutionized our ability to directly observe molecular behaviors with ultra-high spatial/temporal resolution and to decouple the elementary processes that were often veiled in ensemble experiments. This review provided an overview of principle and realization of two single-molecule fluorescence techniques that were often used to study the interfacial dynamics. In addition, this review updated recent progress in the discovery and understanding of dynamical anomalies of polymers at solid/liquid interfaces using these single-molecule techniques, emphasizing important elementary processes of diffusion, adsorption, and desorption.