Preparation and electrophoretic response of poly(methyl methacrylate-co-methacrylic acid) coated TiO2 nanoparticles for electronic paper application

Titanium dioxide (TiO₂) nanoparticles were encapsulated with poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) via simple method of coacervation, in order to improve the dispersion stability of the nanoparticles in a dielectric medium and to reduce the density mismatch between TiO₂ and a dielectric medium for a electrophoretic display application. The morphology of PMMA-co-MAA coated TiO₂ nanoparticles were observed via SEM and electrophoretic light scattering (ELS). It was found that density of PMMA coated TiO₂ nanoparticles were reduced by coating process via gas pycnometer. Electrophoretic mobility of the fabricated nanoparticles in a low dielectric medium with charge control agent was measured via electrophoretic light scattering spectrophotometer for potential application in electronic paper technology.     

Investigations of Pulse‐Plasma‐Polymer Coating on TiO2 Nanoparticles and Their Dispersion

An amorphous acrylic acid (AA) polymer coating was generated on TiO₂ nanoparticles through pulse radio frequency (RF) plasma polymerization. The AA plasma synthesis mechanism was studied by its optical emission spectrum. The chemical structures of AA–plasma‐polymer were carefully investigated by Fourier transform infrared spectroscopy (FTIR). The dispersion behaviors of AA‐coated and uncoated TiO₂ nanoparticles in glycol solution were characterized by ultraviolet absorbency and particle size distribution measurements. The results showed that the aggregation of TiO₂ nanoparticles in glycol solution was effectively lowered and the dispersion was improved a lot after AA–plasma‐polymer coating. The pulse plasma coating parameters played an important role in the dispersion enhancement of TiO₂ nanoparticles. By properly regulating the pulse discharge parameters, the system could gain the highest radical–monomer reactions rate, the most compatible functional groups on the nanoparticles, and the best dispersion in the background media.     

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.     

Preparation and characterization of low density polystyrene/TiO2 core–shell particles for electronic paper application

In order to reduce the density mismatch between TiO₂ and the low dielectric medium and improve the dispersion stability of the electrophoretic particles in the low dielectric medium for electrophoretic display application, polystyrene/titanium dioxide (PS/TiO₂) core–shell particles were prepared via in-situ sol–gel method by depositing TiO₂ on the PS particle which was positively charged with 2-(methacryloyloxy)ehyl trimethylammonium chloride (DMC). The morphology and average particle size of PS/TiO₂ core–shell particles were observed by transmission electron microscopy (TEM), scanning electron microscope (SEM) and particle size analyzer. It was found that density of PS/TiO₂ core–shell particles were reduced obviously and the particles can suspend in the low dielectric medium of low density. The PS/TiO₂ core–shell particles can endure ultrasonic treatment because of the interaction between TiO₂ and PS. Zeta potential and electrophoretic mobility of the fabricated core–shell particles in a low dielectric medium with charge control agent was measured to be −44.3 mV and −6.07 × 10⁻⁶ cm²/Vs, respectively, which presents potential in electronic paper application.     

In situ Radical Copolymerization in Presence of Surface‐Modified TiO2 Nanoparticles: Influence of a Double Modification on Properties of Unsaturated Polyester (UP) Nanocomposites

In the preparation of nanocomposites, there is competition between the dispersion of nanoparticles and the formation of agglomerates. In this study, radical copolymerization of ethyl acrylate and methyl methacrylate initiated by 2,2‐azobis (isobutyro) nitrile (AIBN) was performed, in the presence of titanium oxide (TiO₂) nanoparticles modified in a new approach; a good dispersion of the nanoparticles in the unsaturated polyester (UP) matrix was obtained. The TiO₂ nanoparticles were exposed to 3‐(methacryloxy) propyl trimethoxy silane as the coupling agent. The presence of coupling agent‐grafted TiO₂ nanoparticles in the copolymerization process resulted in the formation of a polymeric layer on the surface of the TiO₂ nanoparticles (doubly modified‐TiO₂). The grafting of coupling agent molecules and consequently copolymer macromolecular chains onto the surface of TiO₂ nanoparticles was investigated using Fourier transform infrared (FTIR) analysis. It found that the formation of an acrylate layer on the surface of nanoparticles was successful. Then, unsaturated polyester (UP)/TiO₂ nanocomposites were prepared. The morphology was studied using transmission electron microscopy (TEM). Mechanical properties and ultraviolet visible (UV/VIS) spectroscopy of various samples, including the doubly modified‐TiO₂ nanoparticles, with different nanoparticle inclusions and the unmodified‐TiO₂ nanoparticles, were also investigated. The results showed the doubly modified‐TiO₂ nanoparticles, compared to those of unmodified‐TiO₂, had better nanoparticle dispersion causing improvement in the mechanical properties and UV shielding.     

The dispersion study of TiO2 nanoparticles surface modified through plasma polymerization

In this study, the surface of TiO₂ nanoparticles was modified through plasma polymerization, which is a dry coating method at room temperature. The surface morphology of TiO₂ nanoparticles was characterized by high-resolution transmission electron microscope (HRTEM). The dispersion behavior of TiO₂ nanoparticles in water and ethyl glycol was investigated by laser size distribution and ultraviolet–visible absorption spectrum. TiO₂ nanoparticles were coated with a thin film through plasma polymerization, which prevents the agglomeration and improves the dispersion behavior of TiO₂ nanoparticles.     

Surface-initiated atom transfer radical polymerization from TiO2 nanoparticles

Two kinds of hydrophilic polymers, poly(oxyethylene methacrylate) (POEM) and poly(styrene sulfonic acid) (PSSA), were grafted from TiO₂ nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. Chlorine modified TiO₂ nanoparticles (TiO₂-Cl), the ATRP initiators, were synthesized by the reaction of -OH in TiO₂ with 2-chloropropionyl chloride (CPC). FT-IR, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS) clearly showed that the polymer chains were successfully grafted from the surface of TiO₂ nanoparticles. The hydrophilically modified TiO₂ nanoparticles have a better dispersion in alcohol than unmodified nanoparticles, as revealed by transmission electron microscopy (TEM). It was also found that the polymer grafting did not significantly alter the crystalline structure of the TiO₂ nanoparticles according to the X-ray diffraction (XRD) patterns. Grafting amounts were 10% of the weight for both TiO₂-POEM and TiO₂-PSSA nanoparticles, as determined by thermogravimetric analysis (TGA).     

Preparation and Characterization of Nano‐TiO2 Doped Polystyrene Materials by Melt Blending for Inertial Confinement Fusion

Abstract

Nano‐TiO₂ doped polystyrene (PS) materials (TiO₂‐d‐PS) used for inertial confinement fusion (ICF) targets were prepared by means of melt blending. The effect of the pretreatment process, including coupling agents and ultrasonic dispersion on nano‐TiO₂, was studied. Tensile tests were conducted to evaluate the mechanical properties of the TiO₂‐d‐PS materials. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) was used to characterize the degree of dispersion of nano‐TiO₂ in the PS matrix. Transmission electron microscopy (TEM) and dynamic contact angle (DCA) measurements were introduced to demonstrate the surface state of untreated and pretreated nano‐TiO₂. The results showed that coupling agents improved the interfacial adhesion between the PS matrix and dopants; ultrasonic dispersion contributed to the increase in the tensile properties of the TiO₂‐d‐PS materials. The dispersion stability of nano‐TiO₂ powder and the stability of the TiO₂‐d‐PS materials were significantly enhanced through pretreatment, which was supported by the increase in the DCA when the nano‐TiO₂ was pretreated by the coupling agent. The results of SEM and EDS indicated that the nano‐TiO₂ dispersed homogeneously in the PS matrix. The pretreatment process is an effective way to break the aggregation of nano‐TiO₂, which was confirmed by TEM results. Melt blending is a feasible method to prepare PS doped high Z element ICF target materials.     

Rheology and Dispersion Behavior of Ethylene‐Vinyl Acetate Copolymers/TiO2 Masterbatches Prepared by Melt‐Compounding

The rheology and dispersion behavior of ethylene‐vinyl acetate (EVA) copolymer/TiO₂ masterbatches prepared by melt‐compounding were investigated. The pure EVA exhibits obviously pseudoplastic behavior and the apparent viscosity decreases remarkably at experimental temperatures, especially in the range of 100–500 s^?1. The EVA/TiO₂ masterbatches exhibit similar shear rheology behavior with pure EVA and the apparent viscosities are obviously higher than that of pure EVA when the TiO₂ content is above 10 wt.%. Field‐emission scanning electron microscopy (FE‐SEM) and energy dispersive x‐ray spectroscopy (EDX) show that relatively low TiO₂ loading and moderate shear rate are helpful for the improvement of dispersion behavior of TiO₂ nanoparticles; moreover, the dispersion behavior of TiO₂ greatly influences the melt viscosity. The extensional rheology of pure EVA decreases with increasing extension rate, especially at low melt temperatures. EVA/TiO₂ masterbatches have similar extensional rheology behavior as pure EVA and the TiO₂ loading has almost no influence on the extensional viscosity of materbatches.     

Composite SiO2/TiO2 and amine polymer/TiO2 nanoparticles produced using plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition was used to conformally coat commercial TiO₂ nanoparticles to create nanocomposite materials. Hexamethyldisiloxane (HMDSO)/O₂ plasmas were used to deposit SiO₂ or SiO_xC_yH_z films, depending on the oxidant concentration; and hexylamine (HexAm) plasmas were used to deposit amorphous amine-containing polymeric films on the TiO₂ nanoparticles. The composite materials were analyzed using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). These analyses reveal film composition on the nanoparticles was virtually identical to that deposited on flat substrates and that the films deposit a conformal coating on the nanoparticles. The performance of the nanocomposite materials was evaluated using UV-vis spectroscopy to determine the dispersion characteristics of both SiO_x and HexAm coated TiO₂ materials. Notably, the coated materials stay suspended longer in distilled water than the uncoated materials for all deposited films.     

TiO2 nanoparticle thin film deposition by matrix assisted pulsed laser evaporation for sensing applications

The MAPLE technique has been used for the deposition of nanostructured titania (TiO₂) nanoparticles thin films to be used for gas sensors applications. An aqueous solution of TiO₂ nanoparticles, synthesised by a novel chemical route, was frozen at liquid nitrogen temperature and irradiated with a pulsed ArF excimer laser in a vacuum chamber. A uniform distribution of TiO₂ nanoparticles with an average size of about 10 nm was deposited on Si and interdigitated Al₂O₃ substrates as demonstrated by high resolution scanning electron microscopy-field emission gun inspection (SEM-FEG). Energy dispersive X-ray (EDX) analysis revealed the presence of only the titanium and oxygen signals and FTIR (Fourier transform infra-red) revealed the TiO₂ characteristic composition and bond. A comparison with a spin coated thin film obtained from the same solution of TiO₂ nanoparticles is reported. The sensing properties of the films deposited on interdigitated substrates were investigated, too.     

The role of poly(methacrylic acid) conformation on dispersion behavior of nano TiO2 powder

To exploit the advantages of nanoparticles for various applications, controlling the dispersion and agglomeration is of paramount importance. Agglomeration and dispersion behavior of titanium dioxide (TiO₂) nanoparticles was investigated using electrokinetic and surface chemical properties. Nanoparticles are generally stabilized by the adsorption of a dispersant (polyelectrolyte) layer around the particle surface and in this connection ammonium salt of polymethacrylic acid (Darvan C) was used as dispersant to stabilize the suspension. The dosages of polyelectrolyte were optimized to get best dispersion stability by techniques namely particle charge detector (13.75 mg/g) and adsorption (14.57 mg/g). The surface charge of TiO₂ particles changed significantly in presence of dispersant Darvan C and isoelectric point (iep) shifted significantly towards lower pH from 5.99 to 3.37. The shift in iep has been quantified in terms of free energy of interaction between the surface sites of TiO₂ and the adsorbing dispersant Darvan C. Free energies of adsorption were calculated by electrokinetic data (−9.8 RT unit) and adsorption isotherms (−10.56 RT unit), which corroborated well. The adsorption isotherms are of typical Langmuir type and employed for calculation of free energy. The results indicated that adsorption occurs mainly through electrostatic interactions between the dispersant molecule and the TiO₂ surface apart from hydrophobic interactions.     

Nanostructured carbon nanotube/TiO2 composite coatings using electrophoretic deposition (EPD)

Electrophoretic deposition (EPD) has been used to combine multi-walled carbon nanotubes of diameter in the range 20–30 nm and commercially available TiO₂ nanoparticles (23 nm particle size) in composite films. Laminate coatings with up to four layers were produced by sequential EPD, while composite coatings were obtained by electrophoretic co-deposition of carbon nanotubes and TiO₂ nanoparticles, respectively. Scanning electron microscopy was used to characterize the resultant microstructures. The mechanism of EPD of carbon nanotube/TiO₂ nanoparticle composites is discussed.     

Self-cleaning performance of polycarbonate surfaces coated with titania nanoparticles

The effect of NaOH-etching and UVC-irradiation on the mechanical stability of TiO₂ nanoparticles on polycarbonate (PC) slides was investigated. TiO₂ nanoparticles were found to adhere more strongly on UVC-treated PC than NaOH-etched PC, caused by the increase in the hydroxyl and carboxyl groups on the UVC-treated PC. Although a mechanically strong TiO₂ film was developed on UVC-treated PC, the sheet-like wetting effect and antifogging behaviour were only observed with the film coated on NaOH-etched PC. It was also detected that the film coated onto NaOH-etched PC exhibited a more superior performance in degrading methylene blue than that in the UVC-treated PC system. Evidences from the FTIR and AFM analyses indicated that the performance of TiO₂ films was strongly depended on the leaching rate of PEG.     

Improvement in thermo mechanical and optical properties of in situ synthesized PMMA/TiO2 nanocomposite

In this paper, transparent thin films of nano titania filled Poly(methyl methacrylate) (PMMA) composites were synthesized by solvent casting method using tetra hydro furan as a solvent, with in situ nonaqueous ‘sol-gel’ transformation involving the mixing of titanium isopropoxide (as sol-gel precursor) and methanol. The present research work is focused at studying the effect of titania loading on optical and mechanical behavior of transparent nano hybrid thin films. The effect of nano Titanium dioxide (TiO₂) loading on PMMA morphology was studied by using a scanning electron microscope (SEM). Bowl shaped structures were obtained in pure PMMA thin film, which were deformed on incorporation of TiO₂ nanoparticles. This nanocomposite exhibits enhanced optical and mechanical properties. The peak of UV absorption is blue shifted to 261 and 266?nm with the incorporation of TiO₂. At this wavelength, the absorption is increased up to approximately 397%. The nanocomposites exhibit increased tensile strength up to 40% and modulus up to 16%. Tg of PMMA increased from 84.8 to 86.7?°C on adding 1.25% TiO₂ nanoparticles.     

Preparation of low density TiO2/poly (methyl methacrylate) composite particles by emulsifier-free emulsion polymerization

Based on the 3-(trimethoxysilyl) propylmethacrylate (MPS) modified TiO₂ particles, the TiO₂/poly (methyl methacrylate) (PMMA) composite particles have been prepared successfully via emulsifier-free emulsion polymerization in water. A facile floating-sinking method is proposed to roughly evaluate the composite particles’ density. Chemical component of obtained composite particles was identified by Fourier transform infrared spectra (FTIR). The morphology and grain size of the composite particles were investigated by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Thermal analysis of the composite particles was measured by differential thermal analysis-thermo gravimetric analysis (DTA-TGA). The zeta potential and electrophoretic mobility of composite particles with suitable density in water was measured by dynamic light scattering (DLS).     

Weathering performance of the polyurethane nanocomposite coatings containing silane treated TiO2 nanoparticles

Nano-filled polyurethane coatings were prepared by incorporation of various amounts of untreated and amino propyltrimethoxy silane (APS) treated TiO₂ nanoparticles. TEM and AFM techniques were employed to evaluate dispersion of nanoparticles and surface morphology of the coating, respectively. TEM observations revealed that the APS treated nanoparticles have a better dispersion and smaller agglomeration, compared with their untreated counterparts. AFM images revealed that, surface roughness of the coatings increased with increasing of nanoparticles content, however, at equal level of loadings; coatings containing untreated nanoparticles showed a higher surface roughness.Colour changes (colour coordinates data measurements), mechanical properties and surface morphology of the PU nanocomposite coatings, before and after being exposed to a QUV chamber for 1000 h were studied using various techniques. The results revealed that addition of 0.5 to 1.0 wt.% APS treated TiO₂ nanoparticles reduces photocatalytic activity, and improves the weathering performance PU nanocomposite coatings. Tensile strength measurements showed significant improvement of mechanical properties of PU coatings containing modified TiO₂ nanoparticles. Results also revealed that the colour measurement is a useful technique and non destructive method for evaluation of coating's performance against weathering conditions. The experimental results showed a good correlation between different techniques findings.     

亚纳米厚的氧化铝包裹层可以显著提高负载型金纳米颗粒催化剂的热稳定性

负载型金纳米颗粒催化剂在许多催化反应中展现出非常好的催化活性,但是金纳米颗粒在高温等反应条件下容易烧结团聚,极大地限制了金催化剂的应用。利用原子层沉积技术在Au/TiO₂催化剂表面分别精确沉积了一层超薄的二氧化钛和氧化铝包裹层,并对比研究了包裹层对金纳米颗粒的热稳定性影响。原位红外漫反射CO吸附和x-射线光电子能谱数据证实了氧化物包裹层的存在。发现亚纳米厚的氧化铝包裹层能够在600 C完全避免金纳米颗粒的团聚;相反,二氧化钛包裹层对金纳米颗粒稳定性的提高没有明显效果。通过CO氧化探针反应的活性测试,发现随着煅烧温度的升高氧化铝包裹的Au/TiO₂ 催化剂的活性逐渐提高,表明高温处理可以促进被包裹金原子的暴露并表现出催化活性。提供了提高金纳米颗粒稳定性的有效方法,为拓展金催化剂在条件苛刻的反应中的应用奠定了技术基础.     

Fabrication of TiO2 μ-donuts by sol-gel spin coating using a polymer mask

TiO₂ μ-donuts have been fabricated on glass and silicon substrates using polymer masks in combination with a sol-gel technique. Cylindrical poly(methyl methacrylate) (PMMA) nanopillars have been created using a composite polymer of polystyrene (PS) and PMMA followed by careful removal of the PS. Atomic force microscopy (AFM) analyses show that the height and diameter of the PMMA cylinders used as the mask are 440 ± 5 nm and 2.1 ± 0.2 μm, respectively. The cylindrical PMMA nanopillars have been coated with the sol of the TiO₂ precursor by a spin coating technique and annealed in air at elevated temperature to remove the PMMA mask. Removal of the PMMA mask has resulted in the formation of well ordered μ-donuts of TiO₂ on silicon surfaces. The interior and exterior heights of the TiO₂ μ-donuts are found to be 373 ± 152 nm and 457 ± 136 nm, respectively; and the interior and exterior diameters of the TiO₂ μ-donuts are found to be 1.33 ± 0.63 μm and 2.82 ± 0.50 μm, respectively. X-ray photoelectron spectroscopy (XPS) spectra of the TiO₂ μ-donuts as well as the smooth TiO₂ thin film showed signals from Ti and O confirming the presence of TiO₂ with Ti 2p_3/2 and O 1s peaks at 458.8 eV and 530.4 eV, respectively. The O 1s peak of the TiO₂ μ-donuts shows another peak at binding energy 532.0 eV due to SiO₂, as during annealing, the PMMA evaporates and the Si substrate is exposed. The X-ray diffractometer (XRD) pattern of the smooth TiO₂ thin film indicates that the anatase phase is present, with the characteristic peaks observed at 2θ values of 25.4°, 37.4°, and 48° corresponding to (1 0 1), (0 0 4), and (2 0 0) planes, respectively. UV-vis absorption spectra of TiO₂ μ-donuts on glass showed an unusual absorption of light in the visible region at ∼524 nm in addition to the usual UV absorption at ∼337 nm.     

Optimal design for extending the lifetime of thin film luminescent solar concentrators

This study is concerned with the enhancement of the molecular, weathering stability of two models of thin film luminescent solar concentrators (LSCs). Two model systems of thin film LSCs had been proposed; the first model consists of a transparent PMMA/SiO₂ nanohybrid layer coated on a coumarin doped PMMA substrate. The second model designed as the ordinary configuration in which coumarin dye is dissolved in PMMA/SiO₂ nanohybrid layer then coated on a transparent PMMA substrate. The effect of nanosilica concentration on the prepared models was studied by TEM, SEM, DSC, FT-IR, UV–vis absorption and indoor photodegradation test. The obtained results suggested the first model for a durable design of thin film LSC applications specially in hot regions.