Hydrophobic modification of wood via surface-initiated ARGET ATRP of MMA

To convert the hydrophilic surface of wood into a hydrophobic surface, the present study investigated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) as a method of grafting methyl methacrylate (MMA) onto the wood surface. The wood treated with 2-bromoisobutyryl bromide and with the subsequently attached MMA via ARGET ATRP under different polymerization times (2 h, 4 h, 6 h, 8 h) were examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. All the analyses confirmed that PMMA had been grafted onto the wood surface. Water contact angle measurement proved that the covering layer of PMMA on wood made the surface hydrophobic. Polymerization time had a positive influence on the contact angle value and higher contact angle can be produced with the prolongation of the polymerization time. When the reaction time was extended to 8 h, the contact angle of treated wood surface reached 130° in the beginning, and remained at 116° after 60 s. The ARGET ATRP method may raise an alteration on the wood surface modification.     

Surface modification for the perfluorosulfonate proton-conducting electrolyte membrane

The positively charged ions of palladium particles are obtained by reducing the solution containing metallic ions in the presence of PDDA (poly-diallyldimethylammonium chloride) medium. The nascent palladium particles are dispersed evenly on the surface of the perfluorosulfonate proton-conducting electrolyte membrane and bonded firmly to the activation center of the membrane. The mechanical strength of membrane is greatly enhanced by surface modification. And the methanol diffusion coefficients of the modified membrane are decreased prominently by the deposition of palladium particles on the surface, which serves as a natural barrier for methanol crossing.     

Corona-induced graft polymerization for surface modification of porous polyethersulfone membranes

Graft polymerization of acrylic acid (AA) onto porous polyethersulfone (PES) membrane surfaces was developed using corona discharge in atmospheric ambience as an activation process followed by polymerization of AA in aqueous solution. The effects of the corona parameters and graft polymerization conditions on grafting yield (GY) of AA were investigated. The grafting of AA on the PES membranes was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis. Porosimetry measurements indicate the average pore diameters and porosities of the modified membranes decrease with the increase of the GY. The hydrophilicity and surface wetting properties of the original and modified membranes were evaluated by observing the dynamic changes of water contact angles. It is found that the grafting of AA occurs not only on the membrane surfaces, but also on the pore walls of the cells inside the membrane. The permeability experiments of protein solution reveal that the grafting of PAA endows the modified membranes with enhanced fluxes and anti-fouling properties. The optimized GY of AA is in the range of 150-200 μg/cm². In addition, the tensile experiments show the corona discharge treatment with the power lower than 150 W yields little damage to the mechanical strength of the membranes.     

Surface modification of magnetic metal nanoparticles through irradiation graft polymerization

To tailor the interfacial interaction in magnetic metal nanoparticles filled polymer composites, the surfaces of iron, cobalt and nickel nanoparticles were grafted by irradiation polymerization. In the current report, effects of grafting conditions, including irradiation atmosphere, irradiation dose and monomer concentration, on the grafting reaction are presented. The interaction between the nanoparticles and the grafted polymer was studied by thermal analysis and X-ray photoelectron spectrometry. It was found that there is a strong interfacial interaction in the form of electrostatic bonding in the polymer-grafted nanoparticles. The dispersibility of the modified nanoparticles in chloroform was significantly improved due to the increased hydrophobicity.     

Surface modification of hydroxyapatite with poly(methyl methacrylate) via surface-initiated ATRP

This article describes the fabrication of hydroxyapatite (HAP) nanocomposites grafted with poly(methyl methacrylate) (PMMA). Surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was carried out from hydroxyapatite particles derivatized with ATRP initiators. The structure and properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) measurements, and contact angle analyses. TGA was used to estimate the grafting density of ATRP initiators (0.49 initiator/nm²) and the amount of grafted PMMA on the HAP surface. The contact angle analyses indicated that grafting PMMA onto the HAP surface dramatically increased the hydrophobicity of the surface. Moreover, the HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.     

Zwitterionic monomer graft copolymerization onto polyurethane surface through a PEG spacer

A new zwitterionic surface was obtained by a novel three-step grafting procedure. The zwitterionic monomer was introduced by cerium-induced graft copolymerization in the presence of N,N′-methylene bisacrylamide (MBAA) as cross-linking agent. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the MBAA could stimulate zwitterionic monomer grafting onto the membrane surface. Surface properties were also determined by atomic force microscope (AFM) and water contact angle. The hemocompatibility of the modified PU membranes was evaluated by the activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT). The TT and APTT of PU were significantly prolonged by the zwitterion of sulfobetaine monomer grafting copolymerization. The new polyurethane membrane could have a great potential in biomedical applications.     

Effect of TiO2 nanoparticle size on the performance of PVDF membrane

The comparison of the performance and morphology was carried out between neat PVDF membrane and PVDF composite membranes with nanosized TiO₂ particles of different size. The results of permeability and instrumental analysis illustrated that nanometer size obviously affected the performance and structure of the PVDF membranes. The smaller nanoparticles could improve the antifouling property of the PVDF membrane more remarkably. The surface and cross-section of the membranes were observed with an atomic force microscopy (AFM), a scanning electron microscope (SEM). The TiO₂/PVDF membrane with smaller nanoparticles had smaller mean pore size on its surface and more apertures inside the membrane. X-ray diffraction (XRD) experiments also suggested that smaller TiO₂ nanoparticles had stronger effect on the crystallization of PVDF molecules.     

Organic light-emitting diode performance enhancement via indium tin oxide glass surface modification

A self-assembly monolayer (SAM), with phenyl-triethoxysilane (PTES), was used to modify the indium tin oxide anode for an organic light-emitting diode (OLED) in order to improve the OLED performance. The enhancement of OLED performance is attributed to the blockage of excessive hole injection by PTES, balancing the hole and electron injection numbers. The result indicates that the SAM process reaction time duration greatly affects the OLED performance outcomes. If the reaction time is too long, it will impact on the optical efficiency due to molecular aggregates accumulated on the SAM layers, thus reducing the performance of the OLEDs. The electrical and optical characteristics of the OLEDs are modeled by using the modified Shockley equation. Modified Shockley parameters are extracted to interpret the experimental data with excellent accuracy. Those parameters, both electrical and optical, can be used as the DC level modeling parameters for OLED product design simulations.     

Electroless deposition of silver on synthesized calcite via surface modification

Metallic silver was deposited on the surface of synthesized calcite via a simple electroless deposition method. Calcite with cubic morphology was prepared first by homogeneous precipitation and it was subsequently surface modified using ammonium oxalate. The electroless deposition was carried out using formaldehyde as the reducing agent and silver nitrate as the silver source. Both calcite and the silver deposited calcite were characterized by different techniques. Surface modification of calcite with ammonium oxalate is necessary for the deposition of silver and the size of the deposited silver particles could be controlled by changing the deposition parameters such as concentration of the reagents and the deposition time. Lower concentration of silver ions (e.g. 0.01 M AgNO₃) and shorter deposition times (e.g. 30 min) lead to the formation of silver nanoparticles on calcite.     

Hydrophilic modification of polyethersulfone porous membranes via a thermal-induced surface crosslinking approach

A thermal-induced surface crosslinking process was employed to perform a hydrophilic surface modification of PES porous membranes. Difunctional poly(ethylene glycol) diacrylate (PEGDA) was used as the main crosslinking modifier. The addition of trifunctional trimethylolpropane trimethylacrylate (TMPTMA) into the reaction solutions accelerated the crosslinking progress of PEGDA on PES membranes. The membrane surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and FTIR-ATR spectroscopy. The mass gains (MG) of the modified membranes could be conveniently modulated by varying the PEGDA concentration and crosslinking time. The measurements of water contact angle showed that the hydrophilicity of PES membranes was remarkably enhanced by the coating of crosslinked PEGDA layer. When a moderate mass gain of about 150 μg/cm² was reached, both the permeability and anti-fouling ability of PES membranes could be significantly improved. Excessive mass gain not only contributed little to the anti-fouling ability, but also brought a deteriorated permeability to PES membranes.     

Introduction of amino groups on the surface of thin photo definable epoxy resin layers via chemical modification

The introduction of amine groups on the surface of dielectric resins improves the adhesion with electrochemically deposited metals. In this work, etched epoxy resin surfaces are modified with aliphatic amines via a two step wet chemical reaction approach. First, cyanuric chloride is introduced on the surface. Next, the remaining reactive sites of cyanuric chloride are used to couple an aliphatic polyamine. Both reaction steps are optimized by variation of reaction parameters such as concentration, chemicals, temperature and time. A detailed surface characterization after each reaction step is provided using following techniques: ATR-IR, SEM-EDS, XPS and AFM.     

Surface modification of polyvalent element-containing glasses

Seven soda-lime silicate glasses, each of which contains one of the following polyvalent metals: Fe, Mn, Cu, Ce, Ti, V, and Cr, are oxidized in air and reduced in H₂/N₂ (1/99) at their respective glass transition temperature for some period. A crystalline oxide surface layer is created on the glasses (except the vanadium-bearing glass) under the oxidizing condition, since the metallic ions are oxidized from lower to higher valence state, and thereby calcium ions diffuse outward and react with oxygen ions. In contrast, a silica-rich surface layer is created on the glasses under the reducing condition, since sodium and calcium ions diffuse inward. It is found that the extents of both outward and inward diffusions strongly depend on the type of the polyvalent ions for the same conditions of heat-treatment. Out of the seven polyvalent metals studied in this work, copper induces the highest extent of both the inward and outward diffusion, and hence, the thickest surface layer of both amorphous silica and crystalline alkaline earth oxides. The oxide layer lowers the onset temperature of the primary crystallization. The silica-rich surface layer enhances the chemical resistance of the glass in a hot basic solution.     

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 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.     

Laser-induced surface modification of polystyrene

The modification induced in polystyrene (PS) by the ArF excimer laser radiation has been investigated. Various numbers of the laser pulses of the energies below the material ablation threshold were applied. Changes in the chemical composition of the PS surface layer were studied by the X-ray photoelectron spectroscopy (XPS). Analysis of the morphological changes in the polymer surface layer was performed via the atomic force microscopy (AFM). The contact angles of test liquids (water and diiodomethane) were measured with use of a goniometer while the surface energy (SE) was calculated by the Owens-Wendt method. It was found that the surface energy change was mainly affected by surface roughness caused by the laser radiation and that surface oxidation had not considerably contributed to this change. The increase in the SE was mostly due to its disperse component.     

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.     

Surface modification of metallic Co nanoparticles

Monodisperse Co nanoparticles were synthesized by thermal decomposition in the presence of aluminium alkyls yielding air-stable Co nanoparticles after surface passivation. Several procedures for surface modification of these pre-stabilized, metallic Co nanoparticles are presented, including direct anchoring of surface-active functional groups and biocompatible dextran layers as well as silica and polymer coatings. As a result, individually coated nanoparticles as well as microspheres can be obtained.     

Preparation of Symmetric Network PVDF Membranes for Protein Adsorption via Vapor-Induced Phase Separation

Symmetric network poly(vinylidene fluoride) (PVDF) membranes without a dense skin layer were prepared by vapor-induced phase separation from a PVDF/N,N-dimethylacetamide (DMAc)/water system. The effects of evaporation atmosphere, temperature, and humidity during the preparation of the membranes on their morphologies were investigated by scanning electron microscope (SEM). With low temperature and high humidity, the polymer crystallization mechanism dominated the membrane formation process, and the casting solution formed membranes with symmetric morphologies in the vapor phase containing 0.79% DMAc. The effect of additives on the membrane structure and performance was also investigated. The results of adsorption experiments showed that the binding capacity of bovine serum albumin (BSA) increased with the appearance of a circular network morphology and the decrease of mean pore size of the membrane. With the addition of LiCl to the casting solution, the obtained membrane can adsorb BSA up to 150 μg/cm². Proteins on sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis gels were successfully electro-blotted onto these PVDF membranes. Compared with commercial membranes, the PVDF membranes prepared in this work were more suitable for protein blotting.     

Electron beam induced modification of poly(ethylene terephthalate) films

Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy).     

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.