梯度接触角表面的构建与应用

梯度接触角是梯度表面张力的反映,固体表面的润湿性由表面化学组成和表面微观形貌共同决定。通过表面化学组成和表面微观形貌的梯度化,可制备接触角变化范围不同的梯度接触角表面。本文综述了梯度接触角表面在液滴移动、微流体流动和生物吸附等领域中的应用。梯度接触角表面具有的不平衡杨氏力是促进液滴移动的主要原因,而表面所产生的接触角滞后则阻碍液滴移动;在生物学领域,梯度接触角表面会造成蛋白质和细胞选择性吸附或黏附。最后,简要探讨了梯度接触角表面存在的问题和发展方向。     

Wettability of plasma-polymerized vinyltriethoxysilane film

Plasma-polymerized films of vinyltriethoxysilane were surface characterized using the sessile drop technique. The surface free energy and its components were evaluated using the Owens-Wendt-Kaelble geometric mean method, Wu harmonic mean method, and van Oss, Chaudhury, and Good acid-base theory. Influence of deposition conditions on the surface free energy was demonstrated in the study. Improved wettability of the films was related to the diminished concentration of apolar methyl groups in plasma polymers. An increased concentration of carbonyl and hydroxyl groups resulted in a very small improvement of the polar component.     

Low‐Cost,Thermoresponsive Wettability of Surfaces: Poly(N‐isopropylacrylamide)/Polystyrene Composite Films Prepared by Electrospinning

Low‐cost, responsive poly(N‐isopropylacrylamide)/polystyrene composite films were prepared by a facile electrospinning technique. The surface structures and wettabilities of the composite films are tunable by simply controlling the concentration of polymer. With a proper proportion of each polymer, the wettability of the surface can be switched between superhydrophilicity and superhydrophobicity when the temperature is changed from 20 °C to 50 °C. The combination of a stimuli‐responsive polymer with micro/nanostructures on the surface of the composite film contributes to this unique surface property.

     

激光刻蚀硅表面的形貌及其对浸润性的影响

利用脉冲激光在Si表面刻蚀具有不同宽度和深度的微槽形貌, 通过测量接触角的大小研究其浸润特性, 并分析了形貌与浸润性的关系. 结果表明, 在Si表面刻蚀微槽深度一定的条件下, 刻蚀微槽宽度越宽, 接触角越小; 在Si表面刻蚀微槽宽度一定的条件下, 刻蚀微槽越深, 接触角越大, 最高可达165°. 而且Si表面上刻蚀后产生的细微尖峰结构对其浸润特性有显著的影响. 因此, 利用激光刻蚀表面方法可以在一定程度上调控固体表面的润湿性能.     

Wettability control of a solid surface by utilizing photocatalysis

This paper describes a strategic approach utilizing a photocatalyst to obtain a solid surface with a high level of sustainable wettability (hydrophilicity or hydrophobicity). We clarified that the substances adsorbed on the surface could be successfully removed by photocatalytic oxidation resulting in sustainable high hydrophilic and high hydrophobic states. In addition to the conventional redox reaction, photoinduced wettability conversion plays an inevitable role in obtaining a superhydrophilic state. Both of the aforementioned photoinduced properties can be applied to sustain a high level of hydrophilicity. A superhydrophobic surface can be designed based on the Cassie theory. However, a combination with the usual TiO₂ photocatalyst leads to a decrease in hydrophobicity because the photocatalyst becomes hydrophilic itself as a result of the photoinduced hydrophilic reaction. Utilizing the newly developed hydroxyapatite doped with Ti(IV) ions (TiHAP) photocatalyst, which has a considerably reduced hydrophilic effect, a superhydrophobic surface can be sustained after exposing it to outdoor conditions for a long period. As for sustaining the hydrophobic state, the introduction of a material design based on dynamic wettability leads to the possibility of novel functional materials with a high dynamic hydrophobicity. Our study shows that a high level of wettability (hydrophilic or hydrophobic) of a solid surface as that sustained by biologic action is possible by utilizing photocatalysis. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 279–290; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20154     

Acid-Containing Tyrosine-Derived Polycarbonates: Wettability and Surface Reactivity

Tyrosine-derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4-6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (-COOH) to carboxylate ion (-COO⁻). The surface compositions of imidazole-labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N-hydroxysuccinimide.     

Control over the Wettability of Colloidal Crystal Films by Assembly Temperature

Summary: A facile method to fabricate colloidal crystal films with tunable wettability from an amphiphilic material polystyrene‐block‐poly(methyl methacrylate)‐block‐poly(acrylic acid) is presented. The wettability of the film can be tuned from superhydrophilic (CA, 0°) to superhydrophobic (CA, 150.2°) by varying the assembly temperature, while the position of the photonic bandgap of the colloidal crystal films remains virtually unchanged. The method could open new application fields of colloidal crystals in diverse environments.

The relationship of assembly temperature with water CA (inset is the water droplet profile of the relative water CA).     

Thermally Tunable Surface Wettability of Electrospun Fiber Mats: Polystyrene/Poly(N‐isopropylacrylamide) Blended versus Crosslinked Poly[(N‐isopropylacrylamide)‐co‐(methacrylic acid)]

This work reports on thermally tunable surface wettability of electrospun fiber mats of: polystyrene (PS)/poly(N‐isopropylacrylamide) (PNIPA) blended (bl‐PS/PNIPA) and crosslinked poly[(N‐isopropylacrylamide)‐co‐[methacrylic acid)] (PNIPAMAA) (xl‐NIPAMAA). Both the bl‐PS/PNIPA and xl‐PNIPAMAA fiber mats demonstrate reversibly switchable surface wettability, with the bl‐PS/PNIPA fiber mats approaching superhydrophobic ≥150° and superhydrophilic contact angle (CA) values at extreme temperatures. Weight loss studies carried out at 10 °C indicate that the crosslinked PNIPAMAA fiber mats had better structural integrity than the bl‐PS/PNIPA fiber mats. PNIPA surface chemistry and the Cassie–Baxter model were used to explain the mechanism behind the observed extreme wettability.

     

Mechanism and Influencing Factors of Wettability Alteration of Water-Wet Sandstone Surface by CTAB

Different experimental methods including ellipsometry, zeta potential measurements, imbibition studies, and contact angle measurements were used to study the mechanism and influencing factors of wettability alteration of water-wet sandstone surface caused by CTAB (hexadecyl trimethyl ammonium bromide). Results show that when the concentration of CTAB reaches a certain level (below CMC), due to the electrostatic attraction between the positively charged head groups of CTAB and the negatively charged sandstone surface, the monolayer of CTAB is formed and hydrophobic chains of CTAB molecules are toward the aqueous phase, making the solid surface oil-wet. When the concentration of CTAB continues to increase (above CMC), due to the hydrophobic interaction, the compact bilayer of CTAB is formed and hydrophilic head groups of CTAB molecules are toward the aqueous phase, rendering the solid surface water-wet. The contact angles between the oil–water interface and the surface treated with CTAB increase with the increase of the concentration of NaCl and CaCl_2. Compared to NaCl, the inorganic salt CaCl₂ has a greater impact on the contact angle. In addition, the contact angles increase with the increase of temperature and decrease with the increase of pH value of the aqueous solution.     

Towards Dynamic Control of Wettability by Using Functionalized Altitudinal Molecular Motors on Solid Surfaces

We report the synthesis of altitudinal molecular motors that contain functional groups in their rotor part. In an approach to achieve dynamic control over the properties of solid surfaces, a hydrophobic perfluorobutyl chain and a relatively hydrophilic cyano group were introduced to the rotor part of the motors. Molecular motors were attached to quartz surfaces by using interfacial 1,3‐dipolar cycloadditions. To test the effect of the functional groups on the rotary motion, photochemical and thermal isomerization studies of the motors were performed both in solution and when attached to the surface. We found that the substituents have no significant effect on the thermal and photochemical processes, and the functionalized motors preserved their rotary function both in solution and on a quartz surface. Preliminary results on the influence of the functional groups on surface wettability are also described.     

Effect of Spontaneous and Water-Based Passivation on Components and Parameters of Ti6Al4V (ELI Grade) Surface Tension and Its Wettability by an Aqueous Solution of Sucrose Ester Surfactants

Solid wettability is especially important for biomaterials and implants in the context of microbial adhesion to their surfaces. This adhesion can be inhibited by changes in biomaterial surface roughness and/or its hydrophilic–hydrophobic balance. The surface hydrophilic–hydrophobic balance can be changed by the specifics of the surface treatment (proper conditions of surface preparation) or adsorption of different substances. From the practical point of view, in systems that include biomaterials and implants, the adsorption of compounds characterized by bacteriostatic or bactericidal properties is especially desirable. Substances that are able to change the surface properties of a given solid as a result of their adsorption and possess at least bacteriostatic properties include sucrose ester surfactants. Thus, in our studies the analysis of a specific surface treatment effect (proper passivation conditions) on a biomaterial alloy’s (Ti6Al4V ELI, Grade 23) properties was performed based on measurements of the contact angles of water, formamide and diiodomethane. In addition, the changes in the studied solid surface’s properties resulting from the sucrose monodecanoate (SMD) and sucrose monolaurate (SML) molecules’ adsorption at the solid–water interface were also analyzed. For the analysis, the values of the contact angles of aqueous solutions of SMD and SML were measured at 293 K, and the surface tensions of the aqueous solutions of studied surfactants measured earlier were tested. From the above-mentioned tests, it was found that water environment significantly influences the components and parameters of Ti6Al4V ELI’s surface tension. It also occurred that the addition of both SMD and SML to water (separately) caused a drop in the water contact angle on Ti6Al4V ELI’s surface. However, the sucrose monolaurate surfactant is characterized by a slightly better tendency towards adsorption at the solid–water interface in the studied system compared to sucrose monodecanoate. Additionally, based on the components and parameters of Ti6Al4V ELI’s surface tension calculated from the proper values of components and parameters of model liquids, it was possible to predict the wettability of Ti6Al4V ELI using the aqueous solutions of SMD and SML at various concentrations in the solution.     

Chemical Dual‐Responsive Wettability of Superhydrophobic PANI‐PAN Coaxial Nanofibers

PANI‐PAN coaxial nanofibers have been prepared by electro‐spinning during polymerization. The surface of the resulting nanofibers is superhydrophobic with a water contact angle up to 164.5°. Conductivity of the PANI‐PAN nanofibers is about 4.3 × 10⁻² S · cm⁻¹. The superhydrophobic nanofibers show a chemical dual‐responsive surface wettability, which can be easily triggered by changing pH value or redox properties of the solution. A reversible conversion between superhydrophobicity and superhydrophilicity can be performed in a short time. The strategy used here may provide an easy method to control the wettability of smart surfaces by using properties of low‐cost functional polymers.

     

一维纳米纤维构筑的导电聚合物三维结构及其可控的浸润性

微/纳米结构的导电聚合物由于具有高导电性、易合成以及优异的环境稳定性从而在许多先进的研究领域备受关注,并有望在分子导线、化学和生物传感器、发光器件等领域获得广泛应用。 特别是,复杂的三维自组装结构在获得高性能和功能化的材料方面提供了巨大的潜在应用价值。本文主要介绍了我们利用胶束的软模板和自组装驱动力的协同效应,实现由一维纳米结构组装的三维微米结构导电聚合物方面的研究进展。该制备技巧在于低表面自由能的含氟有机酸具有软模板、掺杂剂、自组装驱动力,以及诱导超疏水性的多重作用实现导电聚合物三维结构的组装和多功能化。介绍了利用环境湿度调整分子的自组装驱动力,实现导电聚合物由一维纳米结构向三维微米结构的组装。此外,还介绍了利用导电聚合物可逆的化学掺杂/脱掺杂机制,实现导电聚合物表面浸润性的可逆转化。最后介绍了在液/液/固三相体系中,通过外加电场刺激,可实现油滴在导电聚合物表面的浸润性和黏附力的控制。     

微纳结构超疏水表面的浸润性分析及设计

微纳复合结构超疏水表面在防污、流动减阻、防冰等领域具有广阔的应用前景，超疏水表面主要通过设计表面化学性质和微观几何结构来获得.合理设计保持表面润湿态的稳定性是其性能发挥的关键.以"液滴-超疏水表面"系统为研究对象，基于最小能原理分析了四种稳定润湿形态，指出影响润湿状态的本征接触角和微观结构参数（相对柱距、相对柱高）.推导了本征接触角的计算公式并对常见材料的本征接触角进行了讨论.结合四种润湿态方程，绘制了随着相对柱距和相对柱高的润湿云图，并将润湿云图归纳为"一点三线六区四状态".分析了相对柱距和相对柱高对浸润状态的影响，结果表明较大的本征接触角、较小的相对柱距和较大的相对柱高能够减小浸润状态发生转变的临界参数，从而拓展超疏水表面的区域范围，有利于超疏水表面的稳定性.利用文献数据验证了上述润湿云图能够准确反映出润湿形态.在上述工作基础之上总结提炼了超疏水表面设计的一般思路.研究结果可为超疏水表面的设计提供理论依据和技术基础.     

Wettability of commercial starches and galactomannans

This paper describes the wettability of basic commercial polysaccharides: starches (potato PS, wheat WS, corn CS, tapioca TS, kuzu KS) and galactomannans (fenugreek gum FG, guar gum GG, tara gum TG, locust bean gum LBG). The study was conducted using the Washburn capillary rise method and thermal drying. This allowed one to determine the material constant C, contact angle θ, surface free energy of solid SFE, and initial moisture content M. The measured values of contact angle θ and surface free energy SFE indicated that potato starch (70.9°, 41.1?mN?·?m^?1) and wheat starch (88.4°, 30.2?mN?·?m^?1) were characterized by the highest and lowest wettability among the examined starches, respectively. In turn, the galactomannans were poorly wettable substances. Their contact angles θ were approximately equal to 90°, showing a slight increase with increasing substitution degree. The observed decrease in surface free energy SFE from 30 to 29.6?mN?·?m^?1 indicated a very minor hydrophobization of their surfaces. Material constant C was practically independent of temperature, and an increase in initial moisture content M in the examined starches and galactomannans proceeded according to the following schemes: CS?相似文献   

Self-Assembled Dipeptide Aerogels with Tunable Wettability

Constructing supramolecular materials with tunable properties and functions is a great challenge due to the complex competition between multiple assembly pathways. Herein, we report that dipeptides can self-assemble into aerogels with entirely different surface wettability through precisely controlling the assembly pathways. Charged groups or aromatic residues are selectively exposed on the surface of their nanoscale building blocks which results either in a superhydrophilic or highly hydrophobic surface. With this special property, single component dipeptide aerogels can play diverse roles in medical care applications. This study suggests great promise in the synthesis of supramolecular materials with different targeted functions from the same molecular unit.     

纳米通道内表面浸润性对气泡的作用

运用分子动力学模拟方法研究了在质量力驱动下不同浸润性壁面纳米通道中气泡的分布及其运动状况, 提出了一种统计纳米通道中气泡运动速度的方法. 结果显示, 在亲水性壁面的纳米通道中, 气泡位于通道中间, 气泡的运动速度接近但小于通道中心流速, 在势能强度较大时, 壁面吸附的分子较多, 气泡也较大, 反之则气泡较小; 对超疏水性壁面, 气泡则位于固壁附近, 两个壁面形成对称的一对气泡, 气泡的运动速度接近但大于边缘速度. 流体总的流动速度随着流体粒子与壁面粒子作用的减弱而增大, 滑移速度则逐渐从负转变为正.