层层组装制备低介电常数超薄膜

低介电常数材料可作为微电子器件的层间或是导线间的绝缘材料，以提高微电子芯片的信号传输速率。在聚合物材料中引入氟元素或引入空洞可以有效降低聚合物材料介电常数。本文利用层层组装的方法在聚合物中引入空洞以降低聚合物材料的介电常数。这样，不仅能够获得低介电常数材料，而且可以得到超薄膜，对于降低电子元件的尺寸、提高芯片的信号传输速率具有实际的应用价值。 对具有笼状结构的八苯代聚倍半硅氧烷（OPS）采取先用发烟硝酸硝化为带有硝基的产物ONPS，然后再以水合肼作为还原剂将硝基还原为胺基的两步反应方法，制得了带有胺基的聚倍半硅氧烷（OAPS）。用NMR、FTIR方法对合成过程从原料、中间产物、及目标产物进行跟踪分析证明反应结束后，OAPS仍然具有完整的笼状结构，并且胺基化很完全。另外，利用发烟硫酸作为磺化试剂，采用一步合成的方法制得了磺化OPS（SOPS）。经NMR、FTIR表征，确认了SOPS的结构，磺酸基是在苯环上Si的间位发生了取代。经XPS分析得知，OPS上约有91％的苯环参与了磺化反应。在合适的条件下SOPS与OAPS都可以溶于水，分别带有负电荷与正电荷。 然后，利用合成的SOPS与聚丙烯胺(PAH)进行组装。当PAH溶液的pH值小于7.5时，SOPS在PAH溶液中产生脱落现象。通过调节PAH溶液的pH值，可以控制SOPS在PAH溶液中的脱落现象。当PAH溶液的pH值为9.0时，SOPS在PAH溶液中不再脱落。紫外数据表明，尽管组装过程中SOPS在PAH溶液中会有部分脱落，但这并不影响SOPS/PAH复合多层膜的组装。当溶液的pH为3.0时，OAPS溶于水中并带有正电荷。带有负电荷的聚对苯乙烯磺酸钠（PSS）、聚丙烯酸（PAcA）分别与带有正电荷的OAPS实现层层组装。经过QCM、Contact Angle、XPS、UV等方法表征，证明OAPS/PSS与OAPS/PAcA复合多层膜组装过程中生长均匀，并且多层膜厚度可控。用椭圆偏振的方法测得OAPS/PAcA多层膜的折光指数，运用Maxwell方程将其转化为介电常数为2.01，较纯聚丙烯酸的介电常数（2.56）有明显的降低。加热处理OAPS/PAcA多层膜，红外（FTIR）光谱数据显示OAPS与PAcA间发生了交联反应，形成新的酰胺键。紫外可见（UV-Vis）光谱数据也表明，加热后的OAPS/PAcA多层膜在强酸性溶液中的稳定性较加热前的样品有极大的提高。 合成了聚酰胺酸，并将其制成可溶于水的聚酰胺酸三乙胺盐（PAAs）。调节PAAs溶液的pH值为7.5，使之带有负电荷，可以与带有正电荷的OctaAmmonium（OA-POSS）纳米粒子进行组装。QCM数据显示，当OA-POSS的pH为4.5时，PAAs与OA-POSS的组装量相当，组装量比较大。UV-Vis、XPS数据表明，OA-POSS与PAAs可以实现层层组装，并且组装均匀，可控。加热交联后，PAAs能够很容易地转化为聚酰亚胺（PI）。 调节溶液的pH值，使豇豆花叶病毒（CPMV）表面带有负电。以聚阳离子的聚二烯丙基二甲基胺盐酸盐（PDDA）和聚丙烯胺（PAH）作为插层材料可以实现PAAs与CPMV的层层组装，制得复合多层膜[PDDA/CPMV+(PDDA/PAAs)m]n和[PAH/CPMV+(PAH/PAAs)m]n。QCM、UV-Vis数据表明，多层组装膜的厚度可以通过改变[PAH/CPMV+(PAH/PAAs)m]或[PDDA/CPMV+(PDDA/PAAs)m]的组装循环层数进行调节。而且，薄膜中CPMV与PAAs的比例也可以通过改变（PAH/PAAs）或（PDDA/PAAs）的循环个数进行调节。得到组装多层膜后，将其进行加热处理。FTIR数据显示，以PAH、PDDA作为插层所制备得到的CPMV/PAAs复合多层膜经过加热处理后，PAAs向PI的转化非常完全。用椭圆偏振的方法测试加热交联前后的多层膜样品[PAH/CPMV+(PAH/PAAs)m]n的厚度及折光指数，可以得知，加热处理后，薄膜的厚度稍有降低。将折光指数用Maxwell方程转化为介电常数为2.32，这一数值比纯聚酰亚胺的介电常数值（3.40）降低很多，归因于聚酰亚胺中引入带有空洞结构的CPMV，使聚酰亚胺的密度降低，从而降低材料的介电常数。

完全疏水涂层的构建及应用研究

超疏水性表面是指水在固体表面的接触角大于150°的表面。这种表面具有很多独特的性质，如防污、防水、自清洁，防腐等。具有良好透光性的超疏水玻璃在很多交通工具如飞机、汽车等挡风玻璃及日常的建筑幕墙玻璃等方面具有广阔的应用前景。制备超疏水表面一般采用两种方法：一种是先在固体表面构建微细结构，再进行低表面能物质修饰；另一种是直接在具有低表面能材料表面构建微细结构。其中构建表面微细结构这一过程使得超疏水材料的制备过程更加繁琐，同时后续步骤有的还需要采用较昂贵的低能表面进行修饰，因而这些方法在实际大规模应用中缺乏可操作性。因此采用简单、快捷的方法直接制备超疏水表面是非常具有研究有意义的。 本文以常见的普通玻璃为基底，通过气液固扩散法，探索了一种采用简单的一步合成法直接在其表面制备出了具有完全疏水性的表面涂层。这种表面由无序排列的甲基硅氧烷聚合物纳米纤维构成，测试的水滴不能在这样的表面进行粘附，具有非常好的疏水性。同时采用FE-SEM、TG-DTA、FT-IR、Contact angle（CA）等手段对制备的涂层表面进行表征并对纳米纤维可能的形成机理进行了探讨，同时对其耐酸碱性、透光性、耐磨性等也进行了初步的研究。采用冷却这种完全疏水的涂层基底从空气中收集水分，发现这种完全疏水的材料比普通的基底材料具有更好的水分收集效率，因而有望将这种材料在除湿机以及空调上得到应用。

Fabrication of Novel Superhydrophobic Surfaces and Water Droplet Bouncing Behavior - Part 1: Stable ZnO-PDMS Superhydrophobic Surface with Low Hysteresis Constructed Using ZnO Nanoparticles

A superhydrophobic surface has many advantages in micro/nanomechanical applications, such as low adhesion, low friction and high restitution coefficient, etc. In this paper, we introduce a novel and simple route to fabricate superhydrophobic surfaces using ZnO nanocrystals. First, tetrapod-like ZnO nanocrystals were prepared via a one-step, direct chemical vapor deposition (CVD) approach. The nanostructured ZnO material was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) and the surface functionalized by aminopropyltriethoxysilane (APS) was found to be hydrophobic. Then the superhydrophobic surface was constructed by depositing uniformly ZnO hydrophobic nanoparticles (HNPs) on the Poly(dimethylsiloxane) (PDMS) film substrate. Water wettability study revealed a contact angle of 155.4 +/- 2 degrees for the superhydrophobic surface while about 110 degrees for pure smooth PDMS films. The hysteresis was quite low, only 3.1 +/- 0.3 degrees. Microscopic observations showed that the surface was covered by micro- and nano-scale ZnO particles. Compared to other approaches, this method is rather convenient and can be used to obtain a large area superhydrophobic surface. The high contact angle and low hysteresis could be attributed to the micro/nano structures of ZnO material; besides, the superhydrophobic property of the as-constructed ZnO-PDMS surface could be maintained for at least 6 months. (C) Koninklijke Brill NV, Leiden, 2010

Wettability designing by ZnO periodical surface textures

A facile and effective aqueous chemical synthesis approach towards well control of periodical ZnO textures in large-scale areas is reported, by which considerable adjusting of surface wettability can be realized. With the assistance of polystyrene spheres monolayer template and morphology control agent, we succeeded in preparing a series of ordered ZnO microbowls with different sag height. It was found that the contact angle could be well adjusted by changing geometry of microbowl. Such novel, ordered arrays are expected to exploit the great potentiality in waterproof or self-cleaning micro/nanodevices, and even microfluidic devices. (C) 2010 Elsevier Inc. All rights reserved.

Experimental Investigation of Pendant and Sessile Drops in Microgravity

The experiments regarding the contact angle behavior of pendant and sessile evaporating drops were carried out in microgravity environment. All the experiments were performed in the Drop Tower of Beijing, which could supply about 3.6 s of microgravity (free-fall) time. In the experiments, firstly, drops were injected to create before microgravity. The wettability at different surfaces, contact angles dependance on the surface temperature, contact angle variety in sessile and pendant drops were measured. Different influence of the surface temperature on the contact angle of the drops were found for different substrates. To verify the feasibility of drops creation in microgravity and obtain effective techniques for the forthcoming satellite experiments, we tried to inject liquid to create bigger drop as soon as the drop entering microgravity condition. The contact angle behaviors during injection in microgravity were also obtained.

Evaporation of Ethanol Drops on a Heated Substrate Under Microgravity Conditions

We present in this paper results obtained from a parabolic flight campaign regarding ethanol sessile drop evaporation under reduced gravity conditions. Drops are created using a syringe pump by means of injection through a PTFE (polytetrafluoroethylene) substrate. The drops are recorded using a video camera and an infrared camera to observe the thermal motion inside the drop and on the heating substrate. The experimental set-up presented in this paper enables the simultaneous visualization and access to the heat flux density that is transferred to the drop using a heat flux meter placed between the heating block and the PTFE substrate. We evidence original thermal spreading phenomena during the ethanol drop creation on a heated PTFE substrate. The drop exhibits specific behaviour which is discussed here. This work is performed in the frame of a French-Chinese collaboration (project IMPACHT) for future experiments in a Chinese scientific satellite.

Effect of acetylation on the properties of corn starch

Acetylated corn starches with different degrees of substitution (DS 0.85, DS 1.78, DS 2.89) were synthesized by the reaction of corn starch with acetic anhydride in the presence of acetic acid under varying reaction temperatures. The product was characterized by FTIR spectroscopy, H-1 NMR, X-ray diffraction and contact angle measurement. Acid-base titration and H-1 NMR methods were employed to determine the degree of substitution of product. FTIR spectroscopic analysis showed that the characteristic absorption intensities of esterified starch increased with increase in the degree of substitution, and the characterized peak of hydroxyl group almost disappeared in the spectrum of DS 2.89 acetylated starch. The detailed chemical microstructure of native starch and acetylated starch was confirmed by H-1 NMR, C-13 NMR and C-13-(1) H-1 COSY spectra.

Gelatin multilayer assembled on the poly(L-lactic acid) surface for better cytocompatibility

Gelatin multilayers were assembled on PLLA substrate at pH 3, 5, and 7, which was below, around, and above the isoelectric point of the amphoteric polymer, using the layer-by-layer assembly technique. The multilayer deposition on the PLLA substrate was monitored by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The XPS, water contact angle, and atomic force microscopy data indicated that the layer thickness, surface hydrophicity, and surface morphology of the gelatin multilayers assembled strongly depended on the pH at which the layers were deposited

Fabrication of Superhydrophobic Cellulose-Based Materials through a Solution-Immersion Process

An industrial waterproof reagent [(potassium methyl siliconate) (PMS)] was used for fabricating a superhydrophobic surface on a cellulose-based material (cotton fabric or paper) through a solution-immersion method. This method involves a hydrogen bond assembly and a polycondensation process. The silanol, which was formed by a reaction of PMS aqueous solution with CO2, Was assembled on the cellulose molecule surface via hydrogen bond interactions. The polymethylsilsesquioxane coatings were prepared by a polycondensation reaction of the hydroxyl between cellulose and silatiol. The superhydrophobic cellulose materials were characterized by FTIR spectroscopy, thermogravimetry, and surface analysis (XPS, FESEM, AFM, and contact angle measurements).

Layer-by-layer assembly of gelatin

Electrostatic assembly of one species can be realized using gelatin as a polyampholyte. Under suitable conditions where the electrostatic attraction and repulsion were both significant and in balance, linear growth of multilayers driven by electrostatic interactions was sustained over many successive assembly steps, and the maximum amount of adsorption of each layer was reached when the solution pH was around the isoelectric point. The rearrangement of the adsorbed chains after drying was confirmed by contact angle analysis. In addition with only one species involved, the assembled thin films should be chemically uniform rather than layered.

Selective oxidation of cyclohexane with hydrogen peroxide in the presence of copper pyrophosphate

Liquid phase oxidation of cyclohexane was carried out under mild reaction condition over copper pyrophosphate catalyst in CH3CN using hydrogen peroxide as an oxidant at the temperature between 25 and 80 degrees C. The copper pyrophosphate catalyst was characterized by means of XRD, FT-IR and water contact angle measurement. It was found that appropriate surface hydrophobicity is the key factor for the excellent performance of the catalyst. In addition, a significant improvement for the cyclohexane conversion in the presence of organic acid was observed.

WETTABILITY OF EPOXY RESIN ON CARBON FIBER

The micrographs of epoxy resin on single carbon fiber at room temperature and the temperature dependent contact angle on single carbon fiber were investigated using field environmental scanning electron microscope (FESEM). The results showed that the contact angle decreases significantly with increasing temperature. The advantage of this experimental approach was that can directly reflected the wettability of epoxy resin to fiber. But the experimental process was complicated, and there were many influence factors. The reason is that the wettability of epoxy resin on parallel sheet can be improved at higher temperatures. The spreading procedures for the epoxy resin droplet on carbon fiber cluster were observed by means of drop shape analysis system ( DSA) in parallel and perpendicular directions of the aligned fibers.

Super-hydrophobicity of silica nanoparticles modified with vinyl groups

Super-hydrophobic films with vinyl-modified silica nanoparticles (V-SiOx-NPs) were successfully prepared. The rough surface, which was composed of microstructures of disordered V-SiOx-NPs and nanostructures on the surface of V-SiOx-NPs, rather than the chemical composition devoted to the super-hydrophobicity of film. The relationship between contact angle and diameter of V-SiOx-NPs was then investigated. The sessile contact angles (CA) of films with 150-1600nm V-SiOx-NPs were around 166 regardless the diameter, while the film with 85 nm V-SiOx-NPs had the lowest CA of about 158. The packing manner of V-SiOx-NPs determined the air fraction on the surface and then the CA.

Preparation and Characterization of Melt Grafting 2-acrylamido-2-methyl-1-propanesulfonic Acid onto Pre-Irradiated Linear Low Density Polyethylene

Linear low density polyethylene (LLDPE) was functionalized with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) by using -ray pre-irradiation in air in a twin-screw extruder. Fourier-transformed infrared spectroscopy (FT-IR) and electron spectroscopy for chemical analysis (ESCA) were used to characterize the formation of LLDPE-g-AMPS copolymers. The content of AMPS in LLDPE-g-AMPS was determined by using element analysis instrument. The effects of concentrations of monomer, reaction temperature and pre-irradiation dose on degree of grafting were investigated. The critical surface tension of LLDPE-g-AMPS was measured by using contact angle method. The influences of the degree of grafting on crystallization properties were studied by using DSC. Compared with neat LLDPE, the crystallization temperature increased about 4C, and crystallinity decreased with increasing degree of grafting. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at the same crystallization temperature.

Counterion exchange at the surface of polyelectrolyte multilayer film for wettability modulation

Counterions present at the surface of polyelectrolyte multilayers (PEMs) were utilized for modulation of surface wettability via ion exchange. The PEM film was dipped in aqueous solutions of different anions, respectively, and the water contact angle of the surface varied from about 10 degrees to 120 degrees, depending on the hydration characteristics of the anion. The ion exchange mechanism was verified by X-ray photoelectron spectroscopy. The process was rapid and reversible. Ionic strength of the polyelectrolyte solution used for preparing the PEMs was found to be crucial to the surface wetting properties and the reversibility and kinetics of the process, and the effects were correlated to the surface density of the excess charge and counterion. This work provides a general, facile and rapid approach of surface property modulation.