Surface modification of magnesium aluminum hydroxide nanoparticles with poly(methyl methacrylate) via one-pot in situ polymerization

Hydrophobic magnesium aluminum hydroxide composite particles (PMMA-MAH) were obtained by means of grafting poly(methyl methacrylate) (PMMA) onto the surface of magnesium aluminum hydroxide(MAH) nanoparticles after a novel type of phosphate coupling agent (DN-27) modification. The introduction of functional double bonds was firstly conducted on the surface of nanoparticles by DN-27 modification, followed by one-pot in situ polymerization on the particles surface using methyl methacrylate (MMA) as monomer, azoisobutyronitrile (AIBN) as initiator and sodium dodecyl sulfate (SDS) as stabilizer to graft PMMA on the surface of DN-27-modified MAH particles. The obtained composite particles were characterized by field-emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD). The results show that the organic macromolecule PMMA could be successfully grafted on the surface of DN-27-modified MAH nanoparticles and the thermal stability of the PMMA-MAH composite particles had been improved. Compared with unmodified blank MAH sample, the product obtained with this method possesses better hydrophobic properties such as a higher water contact angle of 108° and a well dispersion.     

Surface treatment of magnesium hydroxide to improve its dispersion in organic phase by the ultrasonic technique

Micron magnesium hydroxide [Mg(OH)₂] was modified by means of ultrasonic method with stearic acid (SA) as modifier in water. The Fourier transform infrared spectroscopy (FT-IR) and element analysis showed all SA was bonded upon the surface of the Mg(OH)₂ forming a coating layer and no free SA was detected after the modifying process. The thickness of coating SA on the Mg(OH)₂ was determined by X-ray photoelectron spectroscopy (XPS). Compared with the unmodified Mg(OH)₂, the modified Mg(OH)₂ had better dispersion property in xylene, slower sedimentation velocity of dilute suspension in xylene and lower viscosity of suspension in paraffin liquid. The results showed that the modified Mg(OH)₂ could be dispersed much better than the unmodified Mg(OH)₂ in organic phase.     

微模塑法制备PMMA球面微透镜阵列

借助微透镜及其阵列的光学器件,采用软刻蚀技术中的微模型方法成功制备了聚甲基丙烯酸甲酯(PMMA)的柱体及球面微透镜阵列,并对该微透镜阵列进行了光学显微和SEM分析．通过考察制备过程中的影响因素,探讨了减少阵列缺陷和提高光学性能的适宜参数．并对该透镜阵列的光学成像性能进行了初步研究．     

Surface modification of porous poly(tetrafluoraethylene) film by a simple chemical oxidation treatment

A simple, inexpensive and environmental chemical treatment process, i.e., treating porous poly(tetrafluoroethylene) (PTFE) films by a mixture of potassium permanganate solution and nitric acid, was proposed to improve the hydrophilicity of PTFE. To evaluate the effectiveness of this strong oxidation treatment, contact angle measurement was performed. The effects of treatment time and temperature on the contact angle of PTFE were studied as well. The results showed that the chemical modification decreased contact angle of as-received PTFE film from 133 ± 3° to 30 ± 4° treated at 100 °C for 3 h, effectively converting the hydrophobic PTFE to a hydrophilic PTFE matrix. The changes in chemical structure, surface compositions and crystal structure of PTFE were examined by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), respectively. It was found that the F/C atomic ratio decreased from untreated 1.65-0.10 treated by the mixture at 100 °C for 3 h. Hydrophilic groups such as carbonyl (CO) and hydroxyl (OH) were introduced on the surface of PTFE after treatment. Furthermore, hydrophilic compounds K_0.27MnO₂·0.54H₂O was absorbed on the surface of porous PTFE film. Both the introduction of hydrophilic groups and absorption of hydrophilic compounds contribute to the significantly decreased contact angle of PTFE.     

Surface and core modification of carbon fibers

Thermal and thermochemical treatments with amines have been shown to improve both the mechanical strengths of carbon fibers and their interfacial bonding forces with polymer matrix. In this report, the wettabilities of the surface-treated carbon fibers were studied by dynamic contact angles with epoxy resin. Two mechanisms occur during the fiber modification processes, namely, the fiber core restructuring and surface etching. The former occurs at elevated temperature and increases the fiber strength significantly. When surface reaction occurs, the number of surface oxides increases to improve the surface wettabilities, which may be observed by the decreased dynamic contact angles. Accompanying the etch-cleaning effects, the fiber strength would also increase initially. Deeper penetration of amine would destroy the graphite crystallinity on fiber surfaces and lower the fiber strength.     

Surface modification of polymethyl methacrylate intraocular lenses by plasma for improvement of antithrombogenicity and transmittance

To improve antithrombogenicity and reduce ultraviolet transmittance, polymethyl methacrylate intraocular lenses (PMMA IOLs) were pretreated with Ar plasma and combined with heparin (Hp), with polyglycol (PEG) and with both Hp and PEG in a plasma atmosphere. The resulting modified PMMA IOLs denoted as PEG-PMMA, Hp-PMMA and Hp-PEG-PMMA were characterized by attenuated total reflectance Fourier transfer infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), contact angle (CA) and platelet adhesion experiments. The results indicated that Hp and PEG had been successfully immobilized onto the surfaces of PMMA IOLs. Antithrombogenicity was improved remarkably and ultraviolet transmittance was reduced as well.     

Surface modification of a biomedical polyethylene terephthalate (PET) by air plasma

In this work, low-pressure air plasma has been used to improve polyethylene terephthalate (PET) surface properties for technical applications. Surface free energy values have been estimated using contact angle value for different exposure times and different test liquids. Surface composition and morphology of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Surface topography changes related with the etching mechanism have been followed by weight loss study. The results show a considerable improvement in surface wettability and the surface free energy values even for short exposure times in the different discharge areas (discharge area, afterglow area and remote area), as observed by a remarkable decrease in contact angle values. Change of chemical composition made the polymer surfaces to be highly hydrophilic, which mainly depends on the increase in oxygen-containing groups. In addition to, the surface activation and AFM analyses show obvious changes in surface topography as a consequence of the plasma-etching mechanism.     

Surface modification and characterization of Jordanian kaolinite: Application for lead removal from aqueous solutions

Kaolinite clay was tested for removal of lead ions from aqueous solution. This clay was washed with sulfuric acid solution followed by chemical surface modification using 3-chloropropyltriethoxysilane and sodium hydroxide. XRF results showed that silica to alumina ratio was 2.8:1 for the treated sample compared to 1.6:1 for the raw one.XRD analysis displayed different distinct kaolinite and quartz peaks before treatment while kaolinite peaks were diminished after the treatment. SEM morphology indicated that the raw kaolinite appears as plate structure with no local pores on the plates. However, after treatment the surface was found to have micropores.Different adsorption isotherm models were applied to the experimental data and found that Shawabkeh-Tutunji equation best fit these data adequately. It was also found that chemisorption took place at the surface of the modified kaolinite with maximum adsorption capacity of 54.35 mg/g.     

Surface modification of porous poly(tetrafluoroethylene) film via cold plasma treatment

In this study, cold plasma technology was applied for the surface modification of porous polytetrafluoroethylene (PTFE) film to improve the hydrophilicity. The surface properties of PTFE, modified by air, helium (He) or acrylic acid (AAc), were investigated with scanning electron microscopy (SEM), scanning probe microscope (SPM), in situ X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. The changes of the surface property before and after plasma treatment were discussed. According to SEM and SPM measurements, the surface roughness increased at different levels after plasma treatment. Compared to air and AAc plasma treatment, the He plasma treatment introduced large amounts of oxygen into the surface, as known from XPS results. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly improved due to the surface roughness and changes of chemical elements on the PTFE surface.     

Surface, interface and stacking fault energies of magnesium from first principles calculations

Properties of magnesium have been calculated for bulk, surface and stacking faults, regarded as homogeneous interfaces, using density functional theory within a plane wave pseudopotential technique. Using a supercell approach, stacking fault energies have been determined for intrinsic, extrinsic and twin-like structures for the basal plane together with generalised stacking fault energies on basal, pyramidal and prismatic planes.     

埋层界面和空气表面和频光谱信号贡献的调控

本文研究表明通过膜厚控制和表面等离激元增强方法可有效区分隐藏界面和空气表面的和频振动光谱信号. 以氟化钙基底支撑的PMMA薄膜为模型,观察到隐藏界面和空气表面对和频信号贡献的变化. 通过监控羰基和甲基伸缩振动基团,发现薄PMMA膜的和频信号来自PMMA/空气表面的化学基团-CH₂、-CH₃、-OCH₃和C=O,而厚PMMA膜的和频信号则来自基底/PMMA埋层界面的-OCH₃和C=O基团. 随制膜浓度增大,埋层界面C=O基团的取向角从65°下降到43°,且浓度大于或等于0.5 wt%时,取向角等于45°±2°. 相比之下,空气表面C=O的取向角落在21°∽38°之间. 在金纳米棒存在条件下,表面等离激元可以极大地增强和频信号,尤其是来自埋层界面信号.     

Surface modification of polyimide films using unipolar nanosecond-pulse DBD in atmospheric air

DBD-induced surface modification is very versatile to increase the adhesion or hydrophilicity of polymer films. In this paper, the DBD is produced by repetitive unipolar nanosecond pulses with a rise time of 15 ns and a full width at half maximum of about 30 ns. The power densities of the homogeneous and filamentary DBDs during plasma treatment are 158 and 192 mW/m², respectively, which are significantly less than that using ac DBD processing, and the corresponding plasma dose is also mild compared to AC DBD treatment. Surface treatment of polyimide films using the homogeneous and filamentary DBDs is studied and compared. The change of chemical and physical modification of the surface before and after plasma processing has been evaluated. It can be found that both surface morphology and chemical composition are modified, and the modification includes the rise of hydrophilicity, surface oxidation and the enhancement of surface roughness. Furthermore, the homogeneous DBD is more effective for surface processing than the filamentary DBD, which can be attributed to the fact that the homogeneous DBD can modify the surface more uniformly and introduce more polar functional groups.     

容器内角处流体界面特性与Surface Evolver程序适用性的研究

微重力条件下内角处液体行为的研究对于认识表面张力主导的液体行为, 预测和控制空间微重力条件下的液体位置、瞬时状态, 以及对空间流体进行有效的管理等方面都非常重要. 通过分析接触角与流体界面在容器内角处的接触线方向之间的关系, 并与Concus-Finn理论进行比较, 提出了内角处接触线、接触角和几何形状之间相互关联的机理, 并探讨了Concus和Finn等 的相关理论结果的物理内涵. 在此基础上, 进一步将内角处的相关理论结果与Surface Evolver程序得出的数值结果进行了比较, 指出当容器中的内角小于180°时, Surface Evolver程序通过自动划分网格即可比较准确地预言内角处的接触线和液面行为, 但是当内角大于180°时, 自动划分网格得到的数值结果有较大的误差, 需要通过手动划分网格减少网格奇异才能减小误差. 因此, 对于具有复杂几何形状的容器, 需注意网格的奇异性, 并对内角处的液面进行定量的验证, 才能有效判断Surface Evolver程序结果的正确性. 本工作对于深入认识内角处的液面特性和机理, 理解Surface Evolver程序的适用条件, 以及分析微重力条件下容器内角处的液体行为等方面都具有明显意义.     

Surface modification of active metals through atom transfer radical polymerization grafting of acrylics

The objective of this work is to investigate the fundamentals of surface-initiated atom transfer radical polymerization (s-ATRP) on metal substrates. Acrylic polymers were grafted from active metal surfaces such as cold rolled steel (CRS), stainless steel (SS) and nickel (Ni) through s-ATRP. Severe deactivation was found with copper bromide bipyridine catalyst. Controlled polymerization with relatively low polydispersities, 1.18-1.35, was achieved using iron bromide triphenylphosphine catalyst. Polymer films up to 80 nm in thickness were obtained within 80 min. Grafting densities were estimated to be 0.58 chains/nm² for CRS-g-PMMA, 0.55 chains/nm² for Ni-g-PMMA, 0.18 chains/nm² for SS-g-PMMA, and 0.66 chains/nm² for SS-g-PDMAEMA. Electrochemical experiments were also carried out to measure the polarization resistance and corrosion potential of CRS-g-PMMA substrates. Metal surfaces with grafted brush polymer coatings showed significant corrosion resistance. This work demonstrated that the surface-initiated ATRP is a versatile means for the surface modification of active metals with well-defined and functionalized polymer brushes.     

Polymer surface modification and characterization of particulate calcium carbonate fillers

The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of the treating agent. Here, the ultra-fine calcium carbonate is surface treated with 1, 2, 3 and 4 wt.% polyacrylic acid (PAA) synthesized by ourselves, which has strong ionic interaction and is an efficient surface modifier. The PAA coated filler is submitted to the measurement of the surface bonded amount, bonding efficacy, X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography. Maximum efficacy is expected at the monolayer coverage of the surface, which is about 0.6 wt.% according to the calculation based on the way they are aligned and is basically in agreement with the “substrate overlayer” model based on the mole ratio of C²⁸⁶ and C²⁹⁰ taking no account of the possible underestimation because of the inaccuracy or because of the CH_x contamination present originally on the CaCO₃. The initial decrease of the mole ratio of C²⁹⁰/O and C²⁹⁰/Ca with the surface bonded PAA may indicate that the bonding interaction between the polymer and the filler surface is the leaving of one molecular carbon dioxide. The IGC measurement shows that there is a considerable surface tension falling in the case of the PAA modified filler compared with the reference. An abnormal high surface energy in the case of filler treated with 4% PAA is observed.     

Statistical analysis of the effect of dielectric barrier discharge (DBD) operating parameters on the surface processing of poly(methylmethacrylate) film

A dielectric barrier discharge (DBD) plasma, operating in air at atmospheric pressure, has been used to induce changes in the surface properties of poly(methylmethacrylate) (PMMA) films. The relative effects that key DBD operating parameters, specifically: discharge power, electrode gap and duration of exposure have on producing chemical and microstructural changes in the polymer surface region have been investigated. The approach taken involves the application of an orthogonal array experimental design and statistical analysis methodology. The various data sets obtained from these analyses have been used to develop an equation in which induced changes in the surface properties of the DBD modified PMMA films are expressed in terms of the effectiveness of the various processing parameters in producing them.In general, the results obtained clearly indicate that DBD plasma processing is an effective method for the controlled surface modification of PMMA. Relatively short exposures to the atmospheric pressure discharge produces a significant amount of oxygen incorporation at the surface as indicted by a pronounced reduction in water contact angle. Analysis of the role of each of the operating parameters concerned shows that they do indeed have selective effectiveness for inducing resultant surface modification. Duration of exposure to the DBD plasma, expressed here as the number of treatment cycles at a given speed of specimen transit through the electrode gap, was found to play a major role in decreasing the surface wettability of PMMA. Conversely, the magnitude of the discharge power was not a significant parameter in this regard. In contrast, the value of the applied power played the dominant role in achieving the observed enrichment of the surface oxygen abundance, as measured by XPS, with the duration of exposure to the discharge playing a secondary role in this case.The nature and scale of the induced surface changes that originate from the various processing conditions employed have been further considered to determine if an interrelationship exists between them. Non-parametric data analysis indicates that no significant correlation exists between the observed changes in measured polymer wettability and the attendant surface oxygen enrichment. This result suggests that the increase in surface wettability caused by DBD processing, as manifested in a reduced contact angle, is not merely attributable to changes in the surface chemistry. As such, it is postulated that changes in the surface microstructure may also contribute to this change in surface wettability.     

Surface modification of polyacrylonitrile-based carbon fiber and its interaction with imide

In this work, sized polyacrylonitrile (PAN)-based carbon fibers were chemically modified with nitric acid and maleic anhydride (MA) in order to improve the interaction between carbon fiber surface and polyimide matrix. Bismaleimide (BMI) was selected as a model compound of polyimide to react with modified carbon fiber. The surface characteristic changing after modification and surface reaction was investigated by element analysis (EA), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and surface enhanced Raman scattering (SERS). The results indicated that the modification of carbon fiber surface with MA might follow the Diels Alder reaction mechanism. In the surface reaction between modified fibers and BMI, among the various surface functional groups, the hydroxyl group provided from phenolic hydroxyl group and bridged structure on carbon fiber may be the most effective group reacted with imide structure. The results may shed some light on the design of the appropriate surface structure, which could react with polyimide, and the manufacture of the carbon fiber-reinforced polyimide matrix composites.     

Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) elastomer via photo-initiated graft polymerization of poly(ethylene glycol)

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) copolymer biomedical elastomer was covalently grafted with poly(ethylene glycol) methyl ether methacrylate (PEGMA) via a photo-initiated graft polymerization technique. The surface graft polymerization of SEBS with PEGMA was verified by ATR-FTIR and XPS. Effect of graft polymerization parameters, i.e., monomer concentration, UV irradiation time and initiator concentration on the grafting density was investigated. Comparing with the virgin SEBS film, the PEGMA-modified SEBS film presented an enhanced wettability and a larger surface energy. Besides, the surface grafting of PEGMA imparted excellent anti-platelet adhesion and anti-protein adsorption to the SEBS surface.     

Surface modification and submicron structure of carbon fibers through high current pulse

This paper investigated the behavior of carbon fibers subjected to a ∼20 kA, ∼5 μs high current pulse. It was found that the broken fibers and submicron particles were generated by electrical explosion process. After high current pulsed discharge, the fiber diameter increased significantly, from 5-7 μm to ∼13 μm. Also, the surface rupture of carbon fibers with valleys of hundreds of nanometers was observed. Most notably, the submicron particles appeared with two typical shapes (near-sphere and square). The high current pulsed discharge of carbon fibers can be divided into three stages, namely, heating stage, phase change stage, and explosion stage. Indeed, the electrical explosion process occurred in the last stage of ∼200 ns. The nature behind these results is closely related to the plasma development during the explosion process. The plasma expansion due to a large plasma thermal stress leads to the incomplete explosion. In the explosion stage, the current passing through the fibers exhibited a huge fluctuation, indicating plasma instabilities. Finally, the physical mechanisms, how to affect the surface morphology of carbon fibers, are presented.     

Surface modification of polyethylene terephthalate with albumin and gelatin for improvement of anticoagulation and endothelialization

The surfaces of polyethylene terephthalate (PET) were modified by oxygen plasma-induced and ultraviolet (UV)-assisted acrylic acid (AAc) grafting polymerization, and the carboxyl (COOH) groups on the PET surface was 5.29 × 10⁻⁹mol/cm². Then using the COOH as reacting sites, the molecules of gelatin and bovine serum albumin (BSA) were further co-immobilized on the PET surface. The modified PET surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and surface chemical quantitative analysis. The results showed that the molecules of gelatin and albumin were immobilized on the PET surface. The concentration of gelatin on the gelatin-immobilized PET surface was 2.02 μg/cm². For the gelatin-immobilized PET surface, the human umbilical vein endothelial cells (HUVECs) culture attachment and proliferation ratios were improved, but the anticoagulation became worse proved by platelet adhesion test in vitro and the lactate dehydrogense (LDH) test. After further co-immobilization of albumin with gelatin biomolecules on the PET surface (PET-Gel-BSA), the percent of platelet adhesion in vitro decreased 28% than that on the gelatin-immobilized PET surface, and the cell density on the PET-Gel-BSA film (1.08 × 10⁵ cells/cm²) was significantly higher than that on the control PET surface. This investigation tries to find a method which can construct the anticoagulant surface before the endothelium formation and also accelerate the endothelialization of polymer surface.