Accuracy of the Judd—Ofelt theory

The accuracy of the Judd-Ofelt theory is investigated in several rare earth doped glasses. Using a normalized method to fit the experimental data, we show that an average accuracy of 5 to 15% is often obtained. However, large errors (up to 35%) can be found on some transitions, even in the case of ions usually considered as well described by the theory. These errors tend also to depend strongly on the materials so that prediction of the accuracy of a calculated intensity is difficult. The Judd-Ofelt parameters found with the normalized method may also differ from those computed in the usual way. Moreover, even in relatively close compositions, quality of the fits can largely vary, weakening possible correlations between compositions and Judd-Ofelt parameters.     

Competitive adsorption of collagen and bovine serum albumin—effect of the surface wettability

The competitive adsorption of collagen and bovine serum albumin (BSA) on surfaces with varied wettability was investigated with imaging ellipsometry, and ellipsometry. Silane modified silicon surfaces were used as substrates. The results showed that surface wettability had an important effect on protein competitive adsorption. With the decrease of surface wettability, the adsorption of collagen from the mixture solution of collagen and BSA decreased, while the adsorption of BSA increased.     

The Role of Dielectric Barrier Discharge Atmosphere and Physics on Polypropylene Surface Treatment

Dielectric barrier discharge (DBD) is the discharge involved in corona treatment, widely used in industry to increase the wettability or the adhesion of polymer films or fibers. Usually DBD's are filamentary discharges but recently a homogeneous glow DBD has been obtained. The aim of this paper is to compare polypropylene surface transformations realized with filamentary and glow DBD in different atmospheres (He, N₂, N₂ + O₂ mixtures) and to determine the relative influence of both the discharge regime and the gas nature, on the polypropylene surface transformations. From wettability and XPS results it is shown that the discharge regime can have a significant effect on the surface transformations, because it changes both the ratio of electrons to gas metastables, and the space distribution of the plasma active species. This last parameter is important at atmospheric pressure because the mean free paths are short (m). These two points explain why in He, polypropylene wettability increase is greater by a glow DBD than by a filamentary DBD. In N₂, no significant effect of the discharge regime is observed because electrons and metastables lead to the same active species throughout the gas bulk. The specificity of a DBD in N₂ atmosphere compared to an atmosphere containing oxygen is that it allows very extensive surface transformations and a greater increase of the polypropylene surface wettability. Indeed, even in low concentration and independently of the discharge regime, when O₂ is present in the plasma gas, it controls the surface chemistry and degradation occurs.     

Photografting of polymers onto nanosized silica surface initiated by eosin moieties immobilized onto the surface

The photograft polymerization of various vinyl monomers onto nanosized silica surfaces was investigated. It was initiated by eosin moieties introduced onto the silica surface. The preparation of the silica with eosin moieties was achieved by the reaction of eosin with benzyl chloride groups on the silica surface.These were introduced by the reaction of surface silanol groups with 4‐(chloromethyl)phenyltrimethoxysilane in the presence of t‐butyl ammonium bromide as a phase‐transfer catalyst. The photopolymerization of various vinyl monomers, such as styrene, acrylamide, acrylic acid, and acrylonitrile was successfully initiated by eosin moieties on the silica surface in the presence of ascorbic acid as a reducing agent and by oxygen. The corresponding polymers were grafted from the silica surface. The grafting efficiency (percentage of grafted polymer to total polymer formed) in the photoinitiation system was much larger than that in the radical polymerization initiated by surface radicals; these radicals were formed by the thermal decomposition of azo groups introduced onto the silica surface. It was found that the polymer‐grafted silica gave stable dispersions in good solvents of grafted polymer and the wettability of the surfaces can be easily controlled by grafting of polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 600–606, 2005     

Dual‐responsive copolymer poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] synthesized via photoATRP for surface with tunable wettability

In this work, a series of block copolymers of poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] (PHFBMA‐b‐PDMAEMA) were synthesized via photo‐induced atom transfer radical polymerization (photoATRP) at room temperature. By the introduction of PDMAEMA segment, the hydrophilicity of the silicon wafer surface spin‐coated with PHFBMA homopolymer was improved. Furthermore, the study of tunable surface wettability showed that the surface wettability was pH‐dependent and thermal‐independent at pH 2 and 10. The as‐fabricated surface coated with PHFBMA₁₁₀‐b‐PDMAEMA₁₈₇ showed switchable water contact angle from 85.4° at pH > 4 to 55.0° at pH 2 due to the protonation and deprotonation of tertiary amine groups of PDMAEMA. However, because of the ascendancy of protonated PDMAEMA at pH 2 and the decreased LCST at pH 10, the wettability of the as‐prepared surfaces was thermal‐insensitive. Finally, surface morphology and composition investigation showed that the property of wettability‐controllable surface was not only influenced by surface composition, but also affected by chain conformation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3868–3877     

Wettability of ionic surfactants SDS and DTAB on wheat (Triticum aestivum) leaf surfaces

Abstract

Due to the important use of pesticide formulation, it is necessary to make it clear how ionic surfactant effect the wettability at leaf surface. In this work, we used the sessile drop method to study the wettability of SDS and DTAB on wheat leaf surfaces at different leaf stages, and reveal the relationship between surfactants structures and leaf stages of wheat leaf surfaces on wettability behavior. Results showed that few surfactant molecules adsorbed at the interface at low concentrations. With the concentration increased, the surfactant replaced the air layer partially within the nano/micro structure of leaf surfaces. When the concentration exceeded to CMC, the adsorption of surfactant molecules was saturated at both air-liquid interface and solid-liquid interface, the wetting state was still the transitional state between Cassie-Baxter’s and Wenzel’s state. In all concentrations, the adhesional tension and surface tension showed the linear relationship and the slope values were all below ?1, suggesting there were more surfactant molecules adsorbed at the solid-liquid interface than the liquid-air interface. As SDS is a common wetting agent and DTAB is a common fungicide in agrochemical, this study will provide potential guidance in practical application of pesticide solutions in leaf surface wetting.     

Preparation of Cu-Coated Stainless Steel Surfaces for Superhydrophobic Investigation

Cu-coated stainless steel surfaces containing micro- and nanoscale binary structures with different surface roughness were successfully fabricated by means of a facile one-step electroless plating technology. The resulting surfaces were modified by the low free energy material HFTHTMS (HFTHTMS = (heptadecafluoro-1,1,2,2-tetrahydrodecyl) trimethoxysilane). The experimental results of wettability exhibit that such unmodified surfaces have a strong adhesive force to water droplets, and their contact angles increase with increasing surface roughness, whereas the modified surfaces by HFTHTMS show the superhydrophobic characteristic with contact angles higher than 150° and sliding angles lower than 5°.