Nonsolvents cause swelling at the interface with poly(methyl methacrylate) films

Density profiles of a perdeuterated poly(methyl methacrylate) (dPMMA) film spin-coated on a substrate in water, hexane, and methanol, which are "nonsolvents" for dPMMA, were examined along the direction normal to the interface by specular neutron reflectivity (NR). The interfaces of dPMMA with the liquids were diffuse in comparison with the pristine interface with air; the interfacial width with water was thicker than that with hexane. Interestingly, in water, the dPMMA film was composed of a swollen layer and the interior region, which also contained water, in addition to the diffused layer. The interface of dPMMA with hexane was sharper than that with water. Although there were slight indications of a swollen layer for the dPMMA in hexane, the solvent molecules did not penetrate significantly into the film. On the other hand, in methanol, the whole region of the dPMMA film was strikingly swollen. To conserve mass, the swelling of the film by the nonsolvents is accompanied by an increase in the film thickness. The change in the film thickness estimated by NR was in excellent accord with the results of direct observations using atomic force microscopy (AFM). The modulus of dPMMA in the vicinity of the interfaces with liquids was also examined on the basis of force-distance curves measured by AFM. The modulus decreased closer to the outermost region of the film. The extent to which the modulus decreased in the interfacial region was consistent with the amount of liquid sorbed into the film.     

Achieving Efficient Thick Film All-polymer Solar Cells Using a Green Solvent Additive

Advances in organic photovoltaic technologies have been geared toward industrial high-throughput printing manufacturing, which requires insensitivity of photovoltaic performance regarding to the light-harvesting layer thickness. However, the thickness of light-harvesting layer for all polymer solar cells(all-PSCs) is often limited to about 100 nm due to the dramatically decreased fill factor upon increasing film thickness, which hampers the light harvesting capability to increase the power conversion efficiency, and is unfavorable for fabricating large-area devices. Here we demonstrate that by tuning the bulk heterojunction morphology using a non-halogenated solvent, cyclopentyl methyl ether, in the presence of a green solvent additive of dibenzyl ether, the power conversion efficiency of all-PSCs with photoactive layer thicknesses of over500 nm reached an impressively high value of 9%. The generic applicability of this green solvent additive to boost the power conversion efficiency of thick-film devices is also validated in various bulk heterojunction active layer systems, thus representing a promising approach for the fabrication of all-PSCs toward industrial production, as well as further commercialization.     

声表面波技术检测糜烂性毒剂芥子气的研究

声表面波技术是这些年来得到迅猛发展的一门前沿学科,是传感器技术中引人注目的新兴分支。由于声表面波化学传感器具有体积小、成本低、灵敏度高、易于集成化、智能化、实现远距离检测等多种优点,因而在军用、民用领域显示了良好的应用前景[1-3]。芥子气是糜烂性化学毒剂中最为     

Polymerization Compounding on the Surface of Zirconia Nanoparticles

Zirconia nanoparticles were encapsulated by polyethylene via a polymerization compounding method using a Ziegler-Natta catalyst. The chemical reaction was carried out in an organic solvent under moderate pressure of ethylene monomer. Transmission electron microscopy (TEM) indicated the presence of a thin layer of polymer, about 6 nm, uniformly applied around the particles. However, the thickness of coating layer can be controlled as a function of time and operating conditions of the process. The morphology study using scanning electron microscopy (SEM) as well as TEM revealed that although the nanoparticles seem to be coated individually, some agglomerates, encapsulated by a polymer film, could be observed. The grafting of the catalyst to the original surface of particles was further confirmed by X-ray photoelectron spectroscopy (XPS).     

Water-barrier properties of mixed bis[trimethoxysilylpropyl]amine and vinyltriacetoxysilane films

X-ray and neutron reflectivity were employed to elucidate the morphologies of bis[trimethoxysilylpropyl]amine silane (A) and vinyltriacetoxysilane (V) mixed films on Si wafers at different A/V ratios, and the response of these films to saturated water vapor. Due to its insensitivity to chemical composition, X-ray reflectivity was used to assess the film density, whereas neutron reflectivity was used to probe water absorption and chemical change on exposure to water. NMR was employed to determine the reaction mechanism in neat AV mixtures and stoichiometry of the initial reaction. X-ray reflectivity reveals about 30% void volume in the films with the least void volume detected near stoichiometry. Grazing incidence small-angle scattering (GISAXS) shows that the void volume is at the molecular level, with no distinct pores. Neutron reflectivity on D2O-conditioned films shows that silane film is not an effective water barrier with about 30 vol % water being absorbed with only a slight thickness increase. Most water is physically absorbed in the void space with the least amount being absorbed near the stoichiometric A/V ratio. The scattering length density of the films almost returns to the virgin state after re-dry following D2O vapor exposure. The film thickness, however, remains at the water-vapor-conditioned state. The slight increase in scattering length density and irreversible thickness change after re-dry indicate some reaction with water during D2O conditioning. A D-rich layer is also observed at the air side surface in D2O-conditioned films regardless of A/V ratio.     

In-situ fluorescence imaging of sol-gel thin film deposition

Pyranine was used as a fluorescence probe to monitor the chemical evolution in-situ during thin film deposition by the dip coating process. The sensitivity of the pyranine luminescence to protonation/deprotonation effects was used to quantify changes in the water/alcohol ratio in real time within the depositing film as the substrate was withdrawn from the coating reservoir. The spatially resolved spectral results clearly showed that preferential evaporation of alcohol occurred with increasing distance from the reservoir and that the maximum water content reached rather high values near the drying line. Correlation of the luminescence results with the interference pattern of the drawn films allows the solvent composition in the film to be mapped as a function of film thickness. These experiments demonstrate for the first time that luminescent organic molecules may be applied to the processing science of sol-gel thin film deposition.     

Surface composition and property of film prepared with aqueous dispersion of polyurethaneurea-acrylate including fluorinated block copolymer

The aqueous dispersion of polyurethaneurea-acrylate (PUA) including small amount of fluorinated block copolymers containing carboxyl groups (PATF), which can be dissolved in water, was used to make films and the surface properties of these films were examined. The experimental data show that the modified PUA film exhibits a hydrophobic surface property, although the original surface of PUA film is hydrophilic. The surface composition of the modified PUA film was measured by ATR and XPS. The results indicate that there is a concentration gradient of the fluorine groups along the lines of thickness of the modified film and towards the outmost surface layer, resulting from the migration of fluorinated blocks to the air side surface of the modified PUA film during the film formation process. However, the PUA film can not be modified effectively by adding the sodium salt of PATF, since the urethane groups in the system are easy to occupy on the surface of the film.     

Dynamic characterization of surface topography of plastic films

It is well known that surface roughness plays an important role on the handling and winding of flexible polymer films such as PET which is widely used in various applications. In order to characterize the surface topography of such materials, an air layer is squeezed between a rigid smooth substrate and a film sample. For that purpose a novel experimental set-up has been built. Using an interferometric method and image processing, we have observed the evolution of the air layer thickness and measured its reduction for several configurations and squeezing pressures. It is found that the reduction of the central air layer thickness follows a linear law versus time allowing a parameter, called “dynamic roughness”, to be defined. This parameter, which characterizes the kinetics of the air layer being squeezed, represents the dynamic manifestation of the influence on the flow of more conventional “static” parameters representative of the film roughness. We have developed a theoretical model based on the hypothesis of perfectly flexible film samples and on the concept of equivalent smooth surfaces. The predictions are in good agreement with the experimental results and for each film tested the value of the characteristic parameter associated to its “dynamic roughness” is determined.     

Detection of free surface composition and molecular-level structural development of styrene(S)/butadiene(B) block copolymer films during a solution-to-film process

The surface chemical structure development in solution-cast styrene(S)/butadiene(B) block copolymer films as a function of solvent evaporation time was investigated using sum frequency generation vibrational spectroscopy(SFG).The surface structure formation of the styrene(S)/butadien(B) block copolymer(30 wt% PS) films during the solution-to-film process was found to be controlled mainly by dynamic factors,such as the mobility of the PB block in solution.For SB diblock copolymers,a pure PB surface layer was formed only when the film was cast by dilute toluene solution.With increasing concentration of casting solution,PB and PS components were found to coexist on the film surface,and the morphology of the PB component on the film surface changed from cylindrical rods to spheres.For SBS triblock copolymers,a small amount of PS component existed on the surface even if the film was cast by 1.0 wt% toluene solution.In addition,PS components at the outermost layer of the film increased and the length of PB cylindrical rods on the surface decreased with increasing concentration of casting solution.     

Catalytic Etching of Platinoid Gauzes during the Oxidation of Ammonia by Air. Reconstruction of Surface of Platinoid Gauzes at 1133 K in Air,in Ammonia,and in an NH<Subscript>3</Subscript> + O<Subscript>2</Subscript> Reaction Medium

The structure, morphology, and chemical composition of the surface and near-surface layers of platinoid wires of polycrystalline gauzes, containing Pt (81 wt %), Pd (15 wt %), Rh (3.5 wt %), and Ru (0.5 wt %) after treatment at 1133 K in various media—in air, in ammonia, and after NH3 oxidation in air—are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A thin film is found on the surface of the initial gauze containing an oxide layer of Rh₂O₃ with a thickness of ~2 nm, on the surface of which an inhomogeneous graphite-like layer 10–50 nm thick is located. It is shown that the heat treatment of gauzes in air leads to the partial removal of the surface graphite-like film that forms the reticulated structure on the wire surface. The treatment of gauzes in an ammonia atmosphere leads to the complete removal of the graphite-like and oxide layers and to the growth of metal grains of ~10 μm. After the catalytic reaction of NH3 oxidation, a deep structural rearrangement of the surface layer of the wire takes place, as a result of which crystalline metal agglomerates of ~10 μm are formed. It is supposed that the reaction of NH3 molecules with oxygen atoms penetrated on the defects leads to the local increase of temperature, due to which the metal atoms emerge on the surface and form large crystalline agglomerates and pores in the region of the grain boundaries.     

Characterization of thin polymer‐like films formed by plasma polymerization of methylmethacrylate: A neutron reflectivity study

The microstructure of the plasma‐polymerized methylmethacrylate (ppMMA) films is characterized using neutron reflectivity (NR) as a function of the plasma reaction time or film thickness. Variation in the crosslink density normal to the substrate surface is examined by swelling the film with a solvent, d‐nitrobenzene (dNB). In the presence of dNB, uniform swelling is observed throughout the bulk as well as at the air surface, and silicon oxide interfaces. The results indicate that the MMA film prepared by plasma polymerization (ppMMA) has a uniform crosslink density from air surface to substrate surface. Additionally, the scattering length density of the plasma‐polymerized MMA film (SLD ≈ 0.750 × 10⁻⁶ Å⁻²) is much lower than that of a conventional PMMA film (SLD = 1.177 × 10⁻⁶ Å⁻²). The increase in film thickness following dNB sorption is 7.5% and at least 36% for the ppMMA and PMMA films, respectively. This suggests that the films formed by plasma polymerization are different from conventional polymers in chemical structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2522–2530, 2004     

Characterization of pore structure in a nanoporous low-dielectric-constant thin film by neutron porosimetry and X-ray porosimetry

A small-angle neutron scattering (SANS) porosimetry technique is presented for characterization of pore structure in nanoporous thin films. The technique is applied to characterize a spin-on organosilicate low dielectric constant (low-k) material with a random pore structure. Porosimetry experiments are conducted using a "contrast match" solvent (a mixture of toluene-d8 and toluene-h8) having the same neutron scattering length density as that of the nanoporous film matrix. The film is exposed to contrast match toluene vapor in a carrier gas (air), and pores fill with liquid by capillary condensation. The partial pressure of the solvent vapor is increased stepwise from 0 (pure air) to P0 (saturated solvent vapor) and then decreased stepwise to 0 (pure air). As the solvent partial pressure increases, pores fill with liquid solvent progressively from smallest to largest. SANS measurements quantify the average size of the empty pores (those not filled with contrast match solvent). Analogous porosimetry experiments using specular X-ray reflectivity (SXR) quantify the volume fraction of solvent adsorbed at each step. Combining SXR and SANS data yields information about the pore size distribution and illustrates the size dependence of the filling process. For comparison, the pore size distribution is also calculated by application of the classical Kelvin equation to the SXR data.     

静电纺丝制备空气过滤用抗分层聚酰胺66/聚丙烯腈/聚醚砜(PA-66/PAN/PES)三明治结构膜

通过在经处理的不锈钢网(SSM)上逐层电纺制备了简易有效的聚酰胺66/聚丙烯腈/聚醚砜(PA-66/PAN/PES)复合纤维过滤材料.材料中间层采用以N,N-二甲基甲酰胺(DMF)为溶剂的PAN/PES共混聚合物电纺而成.扫描电子显微镜表征和比表面积测试结果表明, 在相同纺丝条件下PES量的增加有利于减小纤维直径, 增大膜的孔隙率.同时, 通过拉伸实验测量了未带有SSM的膜的机械性能(5.857 MPa).利用PES的良好疏水性, 过滤膜表面具有相对良好的疏水效果, 接触角约为130.58°.在样品厚度尽可能相等的情况下, 通过对实际空气环境中0.3~5 μm的颗粒进行截流测试发现, PAN/PES-3的过滤效率达到且大于99%.通过机械振动和空气反吹考察了过滤膜的再生性能.此外, 还通过使用喷雾喷涂SSM研究了防分层过滤介质的基质.     

The determination of cholesteric pitch from the diffusion profile A new experimental approach

The optical microscopic mass transport (OMMT) method was utilized to determine the cholesteric pitch values of the mixtures of mesogenic and non-mesogenic chiral species in nematic materials. The cholesteric pitch was determined by transient analysis of the diffusion profile established by allowing an initial cholestric composition (solute) to diffuse under semi-infinite linear boundary conditions into an oriented thin film of its corresponding nematic solvent. During the steady-state diffusion, where the initial concentration (pitch) remains constant, the transient analysis of the profile with a polarization microscope exhibits a maximum number of pitch discontinuity domains. The evaluation of the unknown pitch was carried out by extrapolation of the diffusion pitch gradient to the original diffusion source by using the exact relation between the pitch and the film thickness. The method is experimentally simple; at constant temperature and pressure, determination of the pitch depends only on the film thickness. There is a good agreement between the pitch values obtained with this method and those from conventional techniques.     

Solvent‐induced surface instability of thin metal films on a polymer substrate

The solvent‐provoked formation and evolution of thin film buckling‐delamination on a compliant substrate have been studied. The film surface is observed by an optical microscope showing a remarkable dynamic buckling‐delamination development and a subsequent stable branched‐straight state. It is revealed that the initiation, propagation, and the resulting patterns of film buckles are strongly dependent on the solvent type, film stress, interfacial adhesion, and film thickness. The buckling could be controlled further by a reasonable chemical solvent configuration and used to provide useful information for the pattern creation on polymer systems in diverse fields, such as micro/nanofabrication and optics.     

Characterization of oxygen and argon ion flux interaction with PET surfaces by in-situ XPS and ex-situ FTIR

The effects of low (2.5, 0.2 keV) energy reactive oxygen ion bombardment and argon ion bombardment on poly(ethylene terephthalate) thin film (PET) surface chemical composition were studied. PET films have a high potential as a material for biomedical and electrical industries. The source of ions was an ECR Ion Gun with settable acceleration voltages. PET films were sputtered by ion bombardment for variable process time and the modified films were investigated by in-situ X-ray Photoelectron Spectroscopy (XPS) and ex-situ Fourier transform infrared spectroscopy (FTIR). The significant changes in the chemical composition of surface layers were quantitatively studied by XPS. The ion bombardment scissions the chains in PET film surface layers. Selective sputtering of oxygen atoms from PET surface was observed when argon ion flux used. The 0.2 keV and 2.5 keV argon ion decreased O/C ratio from 0.37 to 0.25, 0.04 respectively. This phenomenon is responsible for the creation of carbon-rich up 96 at.% surface layer and the oxygen in ester bonds is detached first. The oxygen 2.5 keV ion bombardment had similar effect as argon ion bombardment; the ratio O/C was decreased. The ester bond was broken first. But oxygen 0.2 keV ion flux irradiation created an oxygen rich surface; the O/C ratio was in increased from 0.37 to 0.46. The changes in surface conductivity were investigated by shifts in C1s binding energy. Good agreement with atomic concentration of carbon in C-C bonds on the films surface was found. The FTIR analyses identified changes in chemical composition but with no obvious correlation to surface changes. Photons from the ion source irradiating the PET film during ion bombardment probably caused the observed changes in FTIR spectra.     

Comprehensive Understanding of Structure‐Controlling Factors of a Zinc Tetraphenylporphyrin Thin Film Using pMAIRS and GIXD Techniques

The performance of an organic electronic device is significantly influenced by the anisotropic molecular structure in the film, which has long been difficult to predict especially for a solution process. In the present study, a zinc tetraphenylporphyrin (ZnTPP) thin film prepared by a solution process was chosen to comprehensively explore the molecular‐arrangement mechanism as a function of representative film‐preparation parameters: solvent, film‐preparation technique, and thermal annealing. The anisotropic structure was first analyzed by using a combination of infrared p‐polarized multiple‐angle incidence resolution spectrometry (pMAIRS) and grazing incidence X‐ray diffraction (GIXD), which readily revealed the molecular orientation and crystal structure, respectively. As a result, the real dominant factor was found to be the evaporation time of the solvent that determines the initial two different molecular arrangements, types‐I and ‐II, while the thermal annealing was found to play an additional role of improving the molecular order. The correlation between the molecular orientation and the crystal structure was also revealed through the individual orientation analysis of the porphyrin and phenyl rings.     

Covalent molecular assembly of oligoimide ultrathin films in supercritical and liquid solvent media

An ultrathin film of oligoimide has been fabricated on amine-modified substrates of silicon and quartz through alternate layer-by-layer (LBL) assembly of pyromellitic dianhydride (PMDA) and diaminodiphenyl ether (DDE), with interlayer links established by covalent bonds. The assembly was formed in supercritical carbon dioxide (SCCO2) and in solution (dimethyl acetamide, DMAc), and the imidization reaction was performed by thermal and chemical methods, in benzene and in the supercritical medium. X-ray photoelectron and UV-visible absorption spectroscopies, atomic force microscopy (AFM), and ellipsometry were employed to study the interfacial chemistry, growth, morphology, and thickness of the assembled film. XPS analysis confirmed the sequential deposition of PMDA and DDE through formation of amic acids. At each deposition step, surface functionalities for the assembly of the next layer were generated. The interfacial chemical reaction was almost complete in the SCF (supercritical fluid) medium, as compared to the conversions observed in conventional assembly. Both the PMDA and DDE molecules were assembled in an organized manner, resulting in uniform surface morphology. Uniform film growth was revealed from the increase of UV absorption intensity and film thickness. The overall growth and quality of the films in SCF medium were greater than that for films formed in DMAc. The results of this novel study show that an environmentally friendly solvent can be used to obtain mechanically robust and thermally stable ultrathin films with little loss of material during the imidization step. In contrast to conventional deposition of the molecular layers that utilizes liquid solvents, use of SCCO(2) avoids solvent effects and posttreatment for solvent removal, while ensuring facile transport during contact.     

Synthesis of nanostructured metal-organic films: surface X-ray radiolysis of silver ions using a langmuir monolayer as a template

An application of the radiolysis method using an X-ray synchrotron beam is developed as a novel approach to the synthesis of metal-organic films with controlled shapes and thickness. We demonstrate that a Langmuir monolayer deposited onto a silver ion containing subphase, irradiated by an incident beam impinging below the critical angle for total reflection, induces the synthesis of a stable nanostructured silver-organic ultrathin film at the air-water interface. The X-ray scattering is also used to monitor in situ the structure of the silver layer during the synthesis process. The layer is observed by atomic force microscopy after its transfer onto a silicon substrate. One observes a film thickness of 4.6 nm, in good agreement with the X-ray penetration depth, about 4.5 nm. The silver structure is oriented by the initial organic film phase. This experiment demonstrates the considerable potential of this approach to produce various controlled metal-organic films with a surfactant self-assembly as a template.