紫外/臭氧法PDMS表面亲水改性机理研究

紫外/臭氧改性法是一种操作简单、成本低廉的PDMS表面亲水改性方法。采用该方法对PDMS表面进行亲水改性,利用接触角测量仪对改性效果进行评价,并与PDMS无臭氧紫外法进行了比较。测试表明PDMS表面经紫外/臭氧法处理12小时后,表面接触角达到60°左右,在空气中放置两周后仍保持较好的亲水性。其改性机理可以通过多种表征手段进行分析。红外光谱测试可以看出,PDMS在经过紫外/臭氧改性后,其表面官能团变化明显,随改性时间延长,疏水基团—CH₃逐渐减少,亲水基团Si—OH和—OH逐步增加,二氧化硅典型红外光谱峰也同时出现。通过扫描电镜和能谱测试可以看出,PDMS表面经过改性产生了二氧化硅为主的硅的氧化物。综合上述结果,紫外/臭氧处理法能够使PDMS表面亲水基团增多,同时生成类玻璃态SiO_x薄层,既改善了PDMS表面的亲水性,又阻止了PDMS表面疏水性的完全恢复,亲水性可以长时间保持。     

Hydrophobic recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification

Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson–Kendall–Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent hydrophobic recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the hydrophobic recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region “collapsed” into a smooth SiO_x layer (final surface roughness <2 nm). PDMS containing heterogeneously distributed, aggregated filler particles (Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the “collapse” of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness ∼140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with contact angle data. JKR experiments showed hydrophobic recovery behavior as anticipated from contact angle measurements. Single pull-off force measurements by JKR and numerical analysis of full-approach JKR curves were in quantitative agreement regarding practical work of adhesion values.     

UV light induced surface modification of HDPE films with bioactive compounds

The development of different techniques for surface modification of polymers becomes popular in a last decade. These techniques preserve useful bulk polymer properties unchanged, while the activation of the polymer surface offers more possibilities for polymer applications.In this work, a new, one-step method for bio-activation of HDPE (high density polyethylene) surface by UV irradiation is presented. HDPE films coupled with selected active compound and a photoinitiator was treated by UV lamp, emitting light at 254 nm.For surface functionalization of HDPE films, the following compounds were employed: 2-aminopyridine (AP), N¹-(2-pyridylaminomethyl)-1,2,4-triazole (TA) and benzocaine (BC). The influence of irradiation time on the extent of surface changes was investigated. The modified polymer surfaces were investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurements, demonstrating successful functionalization of HDPE surface.     

Effects of plasma surface modification on the mechanical properties of carbon fiber and carbon fiber/epoxy composite

_The effect of surface treatment on mechanical properties of carbon fibers has been investigated by application of plasma polymerization of selected monomers in the vapor phase. The role of the fiber-matrix interface on carbon fiber-reinforced epoxy resin composites has also been studied. Composites have been prepared separately by the use of plasma-modified and unmodified carbon fibers in the epoxy resin matrix. The mechanical properties of carbon fibers (Hercules and Grafil) as well as of fiber/epoxy composites were examined by using single filament and three-point bending tests, respectively. It was observed that plasma polymerization treatment at selected plasma conditions led to significant improvement of interlaminar shear and flexural strength values of composites.     

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.     

Quantitative evaluation of interfacial adhesion between fiber and resin in carbon fiber/epoxy composite cured by semiconductor microwave device

Interfacial adhesion between carbon fiber (CF) and epoxy resin in carbon fiber-reinforced epoxy composite, which was prepared by different heating process such as semiconductor microwave (MW) device and conventional electric oven, has been evaluated quantitatively. The interfacial shear strength (IFSS) between CF and epoxy resin, which was an indicator of adhesion on the interface, was measured by a single fiber fragmentation test. The single fiber fragmentation test showed that the IFSSs of the prepared specimens were different by heating methods. In the case of MW process, the curing reaction of epoxy resin on the CF interface would be progressed preferentially due to the selective heating of CF, resulting that the IFSSs of specimens prepared by MW irradiation were increased by enhancing the output power of MW. However, the IFSSs of the specimens were decreased by excessively high output power because the matrix resin on the CF interface was thermally degraded. As results, by optimizing the MW conditions of output power and irradiation time, the IFSS of the sample cured by MW was increased by 21% as compared to oven-heated one. It was found that the interfacial adhesion between CF and epoxy resin would be improved by the MW-assisted curing reaction on the surface of CF.     

Surface modification of PMMA/O-MMT composite microfibers by TiO2 coating

In the present work, poly(methyl methacrylate) (PMMA)/organically modified montmorillonite (O-MMT) composite microfibers were firstly prepared by emulsion polymerization combined with electrospinning, and then coated by nanosize titanium dioxide (TiO₂) using RF magnetron sputter technique. The modified surfaces of PMMA/O-MMT composite microfibers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), UV-vis spectroscopy and drop shape analyzer. Finally, the photocatalytic properties of TiO₂ coated PMMA/O-MMT composite microfiber membranes were evaluated by degradation of methylene blue(MB) under UV illumination. The experimental results revealed that anatase-TiO₂ and rutile-TiO₂ nanoparticles were well spread and physically deposited on the surface of PMMA/O-MMT microfibers, and the wettability of the PMMA/O-MMT composite microfibers was improved after surface modification by sputter coating. Furthermore, the PMMA/O-MMT microfibers membrane coated with TiO₂ performed well in photocatalytic degradation of MB.     

Development of Surface Nano-Crystallization in Alloys by Surface Mechanical Attrition Treatment (SMAT)

Nanometer-sized grain structures that exhibit a large number of grain boundaries on the surface of a bulk material demonstrate excellent properties relative to their coarse-grained (CG) equivalents. Surface modification using surface mechanical attrition treatment (SMAT) is an option that cab be used to tailor the corrosion, tribological, mechanical, and chemical reaction properties of a surface. SMAT is an effective route to create the nanostructured surface layer. The SMAT process has unique advantages compared with the other coating and deposition techniques for surface nanocrystallization. For example, SMAT does not alter the chemical composition of the nanocrystalline surface layer in the matrix. In addition, SMAT has been demonstrated to activate the material surface layer by surface modification and enhance the atomic diffusivity. This article presents a review of the advantages offered by the SMAT technique for the creation of high performance surface layers. The influence of the created nanocrystalline layer on mechanical, physical, and chemical properties is assessed. Developments and the current status of the surface nanolayer that are formed are evaluated from a physical approach. Finally, prospects for the future development of grain refinement on the surface of a material matrix and potential applications are presented.     

Surface and interfacial properties of PVDF/acrylic copolymer blends before and after UV exposure

Morphological and chemical properties of both the surface and interface of poly(vinylidene fluoride)/poly(methyl methacrylate)-co-poly(ethyl acrylate) (PVDF/PMMA-co-PEA) blend films have been investigated before and after the samples were exposed to ultraviolet (UV) irradiation using a xenon arc lamp at 50 °C and 9% relative humidity (RH) for 7 months. Surface and interfacial morphologies were studied by atomic force microscopy (AFM). Chemical composition information was obtained by confocal Raman microscopy, attenuated total reflection-FTIR spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Results show an enrichment of the PVDF material at the air surface, while the acrylic copolymer enriches the interface. Blends having greater than 50% mass fraction of PVDF show little change in the surface morphology after UV exposure for 7 months. However, for a lower PVDF content, blends exhibit significant degradation of PMMA-co-PEA copolymer and a much rougher surface after UV exposure. Microstructural changes in the PVDF spherulites are also observed after UV degradation. It is found that the surface and interfacial morphologies are correlated with the chemical properties.     

Surface functionalization, morphology and thermal properties of polyamide6/O-MMT composite nanofibers by Fe2O3 sputter coating

In the present work, the pure polyamide6 (PA6) nanofiber and PA6/organically modified montmorillonite (O-MMT) composite nanofiber were firstly prepared by a facile compounding process with electrospinning, and then coated by nanosize Fe₂O₃ using magnetron sputter technique. The effects of Fe₂O₃ sputter coating on structures, surface morphology and thermal stability were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), atomic force microscope (AFM) and thermogravimetric analyses (TGA), respectively. The SEM images showed that the diameters of composite nanofiber were decreased with the loadings of O-MMT and the nanosize Fe₂O₃ is well coated on the surface of the homogeneous and cylindrical nanofibers. The XPS spectra reflected the chemical features of the deposited nanostructures. The EDX confirmed the presence of the O-MMT and Fe₂O₃ in the fibers. The AFM observation revealed that there was a remarkable difference in the surface morphology of composite nanofiber before and after sputter coating. The TGA analysis indicated the barrier effects of silicate clay layers and catalysis effects of Fe₂O₃ improved thermal stability properties of the composite nanofiber.     

Surface Modification of Poly (ether ether ketone) with a Medlite C6 (ND-YAG Q-Switched) Skin Treatment Laser

Poly ether ether ketone (PEEK), a synthetic polymer, is expected to be useful as a biomaterial due to its appropriate mechanical, chemical, and biocompatibility properties. However, this polymer is biologically inert, requiring surface modification to improve its adhesion to bone cells for use as a bone substrate. Surface properties, such as roughness and hydrophilicity, are important factors in the adhesion of biomaterials to the surrounding tissue; therefore, in this study, laser treatment was performed for surface modification. The aim of the research described here was to investigate the effect of two laser parameters, fluency and wavelength, on the surface roughness and hydrophilicity to determine the optimum parameters for improving surface adhesion. The surface topography and average roughness (R_a) were investigated by atomic force microscopy (AFM). Surface morphology was also observed with an optical microscope, and the hydrophilicity of the surfaces was investigated with static contact angle tests. The results obtained showed that the samples treated at the wavelength of 532?nm with fluency of 8?J/cm², compared to fluencies of 4 and 12?J/cm², showed improved surface properties. However, in terms of radiation wavelength, the wavelength of 1064?nm at these three fluencies showed the most promising results for enhancing the surface properties of PEEK for bone implant applications.     

The influence of filler modification on its aggregation and dispersion behaviour in silica/PBT composite

In this work, highly dispersed silica is obtained using a precipitation technique from emulsion medium. The selected emulsifier, applied in the process, allows production of silica with almost ideally spherical particles. To examine the tendency to aggregation, the silica powder is treated with commercially available silane coupling agents: 3-mercaptopropyltrimethoxysilane (A-189), N-2-(aminoethyl)-3-aminopropyltrimethoxy silane (A-1120) and 3-methacryloxypropyltrimethoxysilane (A-174). The silica microstructure is characterised by scanning electron microscopy (SEM). Size distribution of primary particles, aggregates and agglomerates structures is determined using dynamic light scattering (DLS) method. Surface treatment of silica generally enhances powder dispersibility. The pristine spherical silica and silica modified with silanes are introduced to poly(butylene terphthalate) (PBT). Dispersion of nanosize precipitated silica particles in PBT matrix is studied by SEM technique. For the visualisation of silica particles covered by polymer layer, the composite fracture surfaces are etched by air-plasma. The agglomerates of untreated silica are not efficiently destroyed during the extrusion process, whereas surface treatment by selected silanes leads to a significant reduction of agglomerate number. However, a large number of small, strongly bonded aggregates still occupied the composite structure.     

Surface modification of poly(dimethylsiloxane) for microfluidic assay applications

The surface of a poly(dimethylsiloxane) (PDMS) film was imparted with patterned functionalities at the micron-scale level. Arrays of circles with diameters of 180 and 230 μm were functionalized using plasma oxidation coupled with aluminum deposition, followed by silanization with solutions of 3-aminopropyltrimethoxy silane (3-APTMS) and 3-mercaptopropyltrimethoxy silane (3-MPTMS), to obtain patterned amine and thiol functionalities, respectively. The modification of the samples was confirmed using X-ray photoelectron spectroscopy (XPS), gold nanoparticle adhesion coupled with optical microscopy, as well as by derivatization with fluorescent dyes. To further exploit the novel surface chemistry of the modified PDMS, samples with surface amine functionalities were used to develop a protein assay as well as an array capable of cellular capture and patterning. The modified substrate was shown to successfully selectively immobilize fluorescently labeled immunoglobulin G (IgG) by tethering Protein A to the surface, and, for the cellular arrays, C2C12 rat endothelial cells were captured. Finally, this novel method of patterning chemical functionalities onto PDMS has been incorporated into microfluidic channels. Finally, we demonstrate the in situ chemical modification of the protected PDMS oxidized surface within a microfluidic device. This emphasizes the potential of our method for applications involving micron-scale assays since the aluminum protective layer permits to functionalize the oxidized PDMS surface several weeks after plasma treatment simply after etching away the metallic thin film.     

Polypropylene surface modification by entrapment of polypropylene-graft-poly(butyl methacrylate)

Surface modification of polypropylene was carried out by entraping a copolymer of polypropylene grafted poly(butyl methacrylate) into polypropylene. The effects of structure of copolymers, contact die and content of modifiers on their surface enrichment were studied by attenuated total reflection infrared spectroscopy (ATR-FTIR), contact angle measurements and scanning electron microscopy (SEM). The results indicated that PPw-g-PBMA could diffuse preferably onto the surface and effectively increase the hydrophilicity of PP. Lower content and higher surface energy die were in favor of the copolymer to enrich on the PP surface. PPw-g-PBMA with low PBMA contents, short length of PBMA distributed in PP with smaller phase domains and favored its selective enrichment on the surface of PP, especially at lower loadings in blends. The modified material exhibited excellent solvent-resistance.     

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.     

A novel terbium composite nanoparticles: Preparation and selective fluorescence determination of chromium(VI)

A highly efficient ultrasonic-assisted method was successfully applied to prepare the strong fluorescence Tb/acetyl acetone (acac)/poly (2-Acrylamidoglycolic acid monohydrate) (PAAM) composite nanoparticles. Based on the fluorescence quenching of Tb/acac/PAAM by Cr(VI), an assay for the selective determination of Cr(VI), without separation of Cr(III), was developed. It is characteristic of very few interferences, stable fluorescence signals (at least 2 h), simple instrument (common spectrofluorometer) and simple step. Under optimal experimental conditions, the fluorescence intensity of the system is linearly proportional to the concentration of Cr(VI) in concentration range of 5-800 ng mL⁻¹ with a correlation coefficient of 0.9983. The limit of detection was found to be 0.5 ng mL⁻¹.The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples with satisfactory results.     

Fabrication of superhydrophobic binary nanoparticles/PMMA composite coating with reversible switching of adhesion and anticorrosive property

Ag-TiO₂-Thiol/Poly(methyl methacrylate) (PMMA) coating has been prepared via adsorbed-layer nanoreactor technique and self-assembling method. The composite coating shows a superhydrophobic property with reversible switching of adhesion. In the UV-vis spectra, absorption appeared in ultraviolet region of 229-293 nm (UVC region) and 320-370 nm (UVA region). Additionally, the stability of the superhydrophobic surface was tested under the following conditions: (1) in basic solution (pH = 14); (2) in acid solution (pH = 1); (3) in artificial seawater. The coating shows stability since the contact angle of the sample still remained higher than 150° in the above conditions. The corrosion resistance of the superhydrophobic surfaces was investigated by electrochemical measurements and the results revealed that the superhydrophobic coatings are anticorrosive well.     

Plasma surface modification of nanofiltration (NF) thin-film composite (TFC) membranes to improve anti organic fouling

Commercial nanofiltration (NF) thin-film composite (TFC) membranes were treated by low-pressure NH₃ plasma, and the effects of the plasma treatment were investigated in terms of the membrane hydrophilicity, pure water flux, salt rejection, protein adsorption, and humic acid fouling. Experimental results indicated that the membrane surface hydrophilicity was increased by the plasma treatment, and changes in the hydrophilicity as well as membrane performance including permeate flux and fouling varied with the original membrane characteristics (e.g., roughness and hydrophilicity). Water flux of plasma treated membranes was the highest with 10 min and 90 W of plasma treatment, and salt rejection was mainly affected by the intensity of the plasma power. Results of bovine serum albumin (BSA) adsorption demonstrated that the protein adsorption decreased with increasing plasma treatment time. The plasma treatment that resulted in more negatively charged surfaces could also better prevent Aldrich humic acid (AHA) attachment on the membrane surface.     

Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -CO functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.