Low pressure plasma‐based approaches to fluorocarbon polymer surface modification

A survey and comparison of several low pressure plasma‐based approaches to fluorocarbon polymer surface modification is reported including “simple” plasma treatment, “grafting to” and “grafting from” plasma activated surfaces, plasma immobilization of predeposited molecules and the adsorption of charged macromolecules on plasma activated surfaces. Examples of each method are discussed in detail based on results from surface analytical experiments using X‐ray photoelectron spectroscopy, ellipsometry, contact angle goniometry, and electrokinetic measurements. All reported examples refer to one and the same experimental setup. This makes the different approaches comparable and helps to exploit a wide range of plasma‐based techniques for a particular goal and a given apparatus. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 100–109, 2007     

Conformation of single polyelectrolyte chains vs. salt concentration: Effects of sample history and solid substrate

Using AFM single polymer molecule experiments we compare conformations of adsorbed on the mica substrate (in the isoelectric point) polyelectrolyte molecules (PE) of poly(methacryloyloxyethyl dimethylbenzylammonium chloride) at different concentrations of Na₃PO₄ salt. We compare the conformations at solid-liquid interface (1) with the conformations of dry samples obtained if the samples of the adsorbed PE were slowly dried (2) and if the PE chains were rapidly deposited and dried on the surface (3). The experiments demonstrate very similar conformations for the cases (1) and (2), while the case (3) differs substantially. The results suggest that the conformations (1) and (2) are formed under strong influence of the substrate. In all cases we observed very pronounced transitions from the extended coil conformation to the pearl necklace-like globule with an increase of salt concentration. The necklace-globules in the cases (1) and (2) appear at a higher salt concentration as compared to the case (3). The strong van der Waals interactions with the solid substrate stabilize the PE globule.     

Halogenation par voie electrochimique de composes ethyleniques—I. Bromation du cyclohexene dans differents solvants nucleophiles

The electrochemical bromination of cyclohexene has been studied in several solvents : acetonitrile, dimethylformamide, dimethylsulfoxide and methanol.In the former three solvents, the first oxidation step of the bromide ion is not modified by the cyclohexene presence, whereas the intensity of the second step depends on the amount of the added cyclohexene. In these three solvents, the oxidation current leads to same value when cyclohexene concentration increases. In methanol, the intensity of the single oxidation step of the Br^? ion increases with the cyclohexene concentration.The preparative electrolyses were realised at the different oxidation steps of Br^?. In acetonitrile only the trans-dibromo compound is formed. In the other solvents beside the 1,2-dibromo cyclohexane, bifunctional compounds are isolated; the solvent participation in the reaction is thus proved.     

The dust particle size distribution in the dust suction pipes of material transfer points

Conclusions A method is proposed for predicting the particle size distribution of the dust in the suction pipes of transfer points for friable materials in relation to the largest particle diameter. The method can be used for deciding the type of dust trap for new and reconstructed dust suction systems.Translated from Ogneupory, No. 8, pp. 23–28, August, 1974.     

Synthesis and behavior of the polymer covering on a solid surface. II. Effect of the adsorbent particle size on adsorption

Adsorption of poly(5-tert-butylperoxy-5-methyl-1-hexen-3-yne-co-maleic anhydride) and poly(styrene-co-maleic anhydride) on the various ultrafine powders (TiO₂, ZnO, Al₂O₃, CaCO₃, aerosil, and quartz powder) was studied. Plateau adsorption amount per unit surface of adsorbent (a^s) decreased with the decreasing of particle size of the adsorbent. The a^s-molecular mass relationship was different for copolymers of low and high molecular mass. The fractal dimension D = 2.5 of adsorbent surface was determined if the particle radius was less than 2.5 μm. Fractal behavior was explained by aggregation of particles. Due to the aggregation the interparticle space (pore) in the area of contact of neighboring particles is inaccessible for the polymer and accessible for the solvent. The experimental isotherm with maximum was employed for estimation of the volume of inaccessible pores 2.4 cm³/g for suspension of aerosil. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 299–305, 1998     

Parallel framework for dense disparity map estimation using Hamming distance

A novel framework for sparse and dense disparity estimation was designed, and the proposed framework has been implemented in CPU and GPU for a parallel processing capability. The Census transform is applied in the first stage, and then, the Hamming distance is later used as similarity measure in the stereo matching stage followed by a matching consistency check. Next, a disparity refinement is performed on the sparse disparity map via weighted median filtering and color K-means segmentation, in addition to clustered median filtering to obtain the dense disparity map. The results are compared with state-of-the-art frameworks, demonstrating this process to be competitive and robust. The quality criteria used are structural similarity index measure and percentage of bad pixels (B) for objective results and subjective perception via human visual system demonstrating better performance in maintaining fine features in disparity maps. The comparisons include processing times and running environments, to place each process into context.     

Effect of Mode Transformation in THz Clinotron

Extension of the theory of a clinotron is developed by use of the scattering matrix of an oversized T-junction on the ends of a slow wave system. The matrix contains elements corresponding to the transformation of slow grating modes into fast ones and vice versa. Those fast waves with low ohmic losses provide strong resonant properties of a clinotron even in the case of strong attenuation of the surface mode. Results of the theoretical simulation are compared with experimental ones and obtained dependencies explain strong resonances in sub-THz clinotrons.     

Synthetic Hydrophilic Materials with Tunable Strength and a Range of Hydrophobic Interactions

The ability to vary, adjust, and control hydrophobic interactions is crucial in manipulating interactions between biological objects and the surface of synthetic materials in aqueous environment. To this end a grafted polymer layer (multi‐component mixed polymer brush) is synthesized that is capable of reversibly exposing nanometer‐sized hydrophobic fragments at its hydrophilic surface and of tuning, turning on, and turning off the hydrophobic interactions. The reversible switching occurs in response to changes in the environment and alters the strength and range of attractive interactions between the layer and hydrophobic or amphiphilic probes in water. The grafted layer retains its overall hydrophilicity, while local hydrophobic forces enable the grafted layer to sense and attract the hydrophobic domains of protein molecules dissolved in the aqueous environment. The hydrophobic interactions between the material and a hydrophobic probe are investigated using atomic force microscopy measurements and a long‐range attractive and contact‐adhesive interaction between the material and the probe is observed, which is controlled by environmental conditions. Switching of the layer exterior is also confirmed via protein adsorption measurements.     

液晶共面取向的等离子处理方法

在受等离子辐照过的一些有机和无机的基板上，获得了高质量的液晶共面取向。与已知的用来改善顶部锚定及预倾角各向同性的等离子处理方法不同，新方法是将等离子束调整到倾斜射向待取向的基板。在所用的辐射参数范围内，所有基板上的LC取向的易取向轴(easy axis)都平行于等离子体传播方向。研究了LC的预倾角和锚定能与等离子束的入射角、辐照时间、能量以及辐照电流密度等的依赖关系。经等离子处理过的基板上，方位角、锚定能与用光取向方法得到的相近，而预倾角与摩擦产生的类似。透过率-电压曲线与等离子处理的和摩擦工艺处理的非常接近。与摩擦取向相同，等离子诱导的取向具有很高的温度和光照的稳定性。也考虑了采用等离子／偏振紫外光和等离子／摩擦处理等组合方法来制作LC图形。