Photographic Properties of Polyethylene Oxide III. Effect of Salt Concentration on the Development Acceleration by PEO.

Development acceleration of iodobromide emulsions by polyethylene oxide (PEO) becomes more pronounced with increasing salt concentration in the developer. If little salt is present in the developer, the degree of acceleration by PEO is low and independent of iodide content of the emulsion. Acceleration is considered to arise from the interaction of PEO with iodide ions released during development.     

Photographic Emulsion Grains with Cores: Part I. Evidence for the Presence of Cores*

Neutral iodobromide emulsions made by the addition of silver nitrate to alkali halides in gelatin may, under certain conditions, contain a proportion of grains with cores of iodobromide phases. The maximum iodide contents (i) of these cores are related to the precipitation temperature (T) by the empirical equation i= 34.5+0.165(T–25). Grains containing such cores show very regular print-out distribution.     

Ag/PEO nanocomposite fabricated in a planar magnetron sputtering

Thin films of silver (Ag)/polyethylene-oxide (PEO) nanocomposite were fabricated by a co-deposition of Ag sputtering particles and PEO thin film on substrates using a planar magnetron sputtering system. The PEO were polymerized from the monomer ethyl glycol dimethyl ether in the magnetron sputtering (MS) plasma. The nanocomposites were characterized by using UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The correlation was performed between the concentrations of Ag and functional group density in Ag/PEO nanocomposites with the discharge parameters, such as sputtering gas pressure and the distance of target-to-substrate. By using AFM and XRD, it is illustrated that the Ag particles distribute uniformly in the body of nanocomposite and remain in atomic status with preferential growth in facet of (111).     

Phase behaviour, mechanical properties and thermal stability of thermosetting polymer blends of unsaturated polyester resin and poly(ethylene oxide)

The results of dynamic mechanical analysis reveal that crosslinked polyester resin (PER)/poly(ethylene oxide) (PEO) blends show a composition dependent glass transition temperature, Tg, which suggests that the blends studied are homogeneous in the amorphous state. The initial dynamic storage modulus, E', decreases with increasing PEO content up to 30 wt% in the blends, whereas E for both the 60/40 and 40/60 PER/PEO blends is close to that for the 80/20 PER/PEO blend and much larger than that for the 70/30 PER/PEO blend. The addition of crystalline PEO has a remarkable effect on the mechanical properties of crosslinked PER. Tensile testing shows that the elongation at break first increases greatly and then decreases slightly, whereas the Young's modulus and the tensile strength first decrease and then increase slightly with increasing PEO content in the blends. The variation of tensile properties was considered to be due to both the plasticization effect and the crystallization effect of PEO in the blends. The impact strength remains almost unchanged with increasing PEO content in the blends studied. No dramatic decrease of thermal stability for PER/PEO blends was observed for the blends with PEO content up to 30 wt%.     

Formulation of PEG-based hydrogels affects tissue-engineered cartilage construct characteristics

The limited supply of cartilage tissue with appropriate sizes and shapes needed for reconstruction and repair has stimulated research in the area of hydrogels as scaffolds for cartilage tissue engineering. In this study we demonstrate that poly(ethylene glycol) (PEG)-based semi-interpenetrating (sIPN) network hydrogels, made with a crosslinkable poly(ethylene glycol)-dimethacrylate (PEGDM) component and a non-crosslinkable interpenetration poly(ethylene oxide) (PEO) component, and seeded with chondrocytes support cartilage construct growth having nominal thicknesses of 6 mm and relatively uniform safranin-O stained matrix when cultured statically, unlike constructs grown with prefabricated macroporous scaffolds. Even though changing the molecular weight of the PEO from 100 to 20 kDa reduces the viscosity of the precursor polymer solution, we have demonstrated that it does not appear to affect the histological or biochemical characteristics of cartilaginous constructs. Extracellular matrix (ECM) accumulation and the spatial uniformity of the ECM deposited by the embedded chondrocytes decreased, and hydrogel compressive properties increased, as the ratio of the PEGDM:PEO in the hydrogel formulation increased (from 30:70 to 100:0 PEGDM:PEO). Total collagen and glycosaminoglycan contents per dry weight were highest using the 30:70 PEGDM:PEO formulation (24.4+/-3.5% and 7.1+/-0.9%, respectively). The highest equilibrium compressive modulus was obtained using the 100:0 PEGDM:PEO formulation (0.32+/-0.07 MPa), which is similar to the compressive modulus of native articular cartilage. These results suggest that the versatility of PEG-based sIPN hydrogels makes them an attractive scaffold for tissue engineering of cartilage.     

Active Polyethylene Oxides: Mechanism of Development

A group of graft co-polymers of polyethylene oxide (PEO) and vinyl acetate (VA) is shown to have a particularly strong inhibiting effect on hydroquinone development, whether added to the emulsion or to the developer. Data are also provided for substituted hydroquinones; much less inhibition is noticed against 2-(N,N-diethylamino-methyl) hydroquinone. Adsorption of the latter and of an integrally coloured PEO to silver powder is demonstrated. The paradoxical difference between the effect of PEO on hydroquinone developer (inhibition) and on a mixed developer, e.g., MQ (acceleration) is discussed The situation is thought to be inexplicable on the charge-barrier theory. An attempt is made to base an hypothesis of PEO action on the following concepts. The active agent of a hydroquinone developer is the semiquinone ion, and this is inhibited by PEO; metol is unaffected by PEO; developing agents are operative by reason of adsorption to latent image silver.     

Metalorganic Vapor-Phase Epitaxy of ZnTe and CdZnTe on GaAs

ZnTe and Cd_{1 – y} Zn _y Te epilayers were grown on GaAs(111)B and GaAs(100) substrates by metalorganic chemical vapor deposition. The structural perfection and surface morphology of the layers were investigated by double-crystal x-ray diffraction and scanning electron microscopy. The effect of deposition conditions on the growth rate, zinc content (y), surface morphology, and structural perfection of the epilayers was studied. The results suggest that the optimal structures for depositing HgCdTe(111)B and HgCdTe(100) are CdTe(111)B/GaAs(111)B and CdTe(100)/ZnTe(100)/GaAs(100), respectively.     

Polymer blends based on PEO and starch: Miscibility and spherulite growth rate evaluated through DSC and optical microscopy

The miscibility and PEO spherulite growth rate in PEO/starch blends (starch from cassava) were evaluated using the depression in the melting point (by DSC) and optical polarized microscope, respectively, and compared to pure PEO. The PEO/starch blend ratio changed from 100/0 to 60/40 (weight/weight). The starch induces changes in PEO crystallization on PEO/starch blends but the crystallization rates do not change linearly to the blend ratio. For 90/10, 80/20, 70/30, 65/35 and 60/40 ratios, lower values for the equilibrium melting temperature were observed as compared to the pure PEO. The obtained interaction parameter value was ? 0.25 by the use of Nishi–Wang equation. The depression in the equilibrium melting temperatures and the negative value for the polymer–polymer interaction parameter suggest that the blends are miscible in the molten state in the range of investigated ratios, except for the 95/05 ratio in which the equilibrium melting temperature increased relative to the pure PEO. The miscibility should be due to the H-bonds among the hydroxyl groups from starch and oxygen atoms of repeat units of PEO.     

A Study on Solid/Melt Interfaces and the Formation of (100) Texture in Solidified FCC Metals

The (100) texture of solidified fcc metals, caused by the preferential (100) dendrite growth, could be closeIy related to solid/melt interfaces which behave differently along different crystallographic orientation. The stability and roughness of {111} and {100} solid/melt interfaces of fcc metals were investigated using a modified Temkin multi-layer model. It is demonstrated that {100}crystal/melt interface is more unstable and rougher than {111} interface. The effect of the stability of crystal/melt interface on the (100) texture formation in solidified fcc metals has been analysed and discussed.     

New insight into PEO modified inner surface of HNTs and its nano-confinement within nanotube

In this study, we demonstrate the use of poly (ethylene oxide) (PEO) for in-situ modification of the inner surface of halloysite nanotubes (HNTs) with water molecules as the hydrogen bond forming medium, as well as the nano-confinement of PEO molecular chains within the nanotube. Before testing, the Soxhlet experiment of PEO/HNTs powder is applied in order to remove the physical adsorption of PEO molecules onto the outmost surface of HNTs. The crystal temperature of PEO changes sharply from 36.9 °C of neat PEO to ?25 °C of PEO in the PEO/HNTs powder and the decomposed temperature of PEO in the PEO/HNTs powder is about 13.1 °C higher than that of neat PEO, which is mainly owing to the nano-confinement effect of PEO within the HNTs with a diameter of about 10 nm. From thermo-gravimetric (TG) analysis, about 7.71 % by weight of PEO has been chemically bonded to HNTs. The hydrogen bonds among PEO, HNTs, and water molecules are evidenced by FTIR and XPS performances. Meanwhile, the binding energy of Al_2p in the innermost surface of HNTs shifts from 74.7 eV in the neat HNTs to 74.5 eV in the PEO/HNTs powder, while that of Si_2p on the outmost surface of HNTs keeps almost constant, indicating that the hydrogen bonds only exists inner the nanotube and PEO molecular chains have been trapped in nano-scale within HNTs, which is in accordance with the DSC and TG observation.     

Influence of growth rate on the structural and morphological properties of TiN, ZrN and TiN/ZrN multilayers

The effect of the deposition rate on the structural and morphological properties of TiN and ZrN single layers and TiN/ZrN multilayers deposited by radiofrequency reactive magnetron sputtering has been studied. The total pressure was kept constant and the growth rate variation was obtained by small difference of nitrogen concentration in the fed gas. The decreasing deposition rate results in a structural change in the thin films from (111) orientation to (100) one. As consequence the surface morphology becomes smoother. Films roughness is strongly related with texture and it decreases with an increase in the (100) X-ray diffraction line intensity. In order to achieve a clear interpretation of our experimental results, the ratio between the N⁺ ions of the plasma and the atoms number reaching the substrate was considered. At high deposition rate with respect to the N⁺ concentration, the chemical potential of transition metal on (100) growth surface is higher than (111) one favouring the (111) orientation of the films. On the contrary, when the growth rate is low with respect to the nitrogen concentration, the chemical potential of transition metal on (111) growth surface is higher than the (100) one leading to a preferential growth in the (100) direction.     

剪切速率对POM/PEO晶/晶共混体系结晶行为的影响

采用偏光显微镜（PLM）联用旋转剪切台,差示扫描量热法（DSC）和X射线衍射（XRD）等研究了剪切速率对POM/聚氧化乙烯（PEO）（50/50）晶/晶共混物结晶行为的影响。实验结果表明,增大剪切速率,POM/PEO（50/50）共混物结晶温度升高,结晶速度加快,形成更多更窄的串晶,POM与PEO分子间缠结包合作用增强...     

On-line concentration and separation of proteins by capillary electrophoresis using polymer solutions

Proteins were separated in 0.6% poly(ethylene oxide) (PEO) solutions using a capillary filled with buffers prior to analysis and were detected by laser-induced native fluorescence using a pulsed Nd:YAG laser. PEO solutions entered the capillary by electroosmotic flow (EOF) during the separation. The composition and concentration of the buffer affected the adsorption of PEO molecules on the capillary surface and, consequently caused changes in the EOF. Short separation times (< 7 min) were achieved on a sample solution of five proteins in a 0.6% PEO solution containing 5 microg/mL ethidium bromide using a capillary pre-filled with 100 mM TRIS-borate (TB) buffers (pH 10,0). We also extended this method for on-line concentration and separation of proteins. Proteins dissolved in low-conductivity media stacked in both TB buffers and in PEO solutions. The peak height was proportional to the injection volume up to 2.1 microL using an 80-cm capillary filled with 400 mM TB buffers. Using large injection volumes (2.1 microL), we achieved a limit of detection (S/N = 3) of 31 pM for carbonic anhydrase, which was a 1696-fold sensitivity enhancement compared to a conventional injection method (1 kV for 10 s). In high-conductivity media (urine matrix), stacking occurred at the boundary between the sample zone and PEO solutions. A urine sample without any pretreatment was analyzed, and after stacking, several peaks were detected. Spiking the urine sample with human serum albumin (HSA) affected the fluorescent intensity of some analytes as a result of interaction with HSA.     

二氧化钛过渡层对脉冲激光沉积钛酸锶钡薄膜微结构和介电性质的影响

选取极薄Ti02作为过渡层,采用脉冲激光沉积法分别在Si(100)和Pt(111)/Ti/SiO2/Si(100)基底上制备了Bao.6Sro.4TiO3(BST)薄膜,研究过渡层对BST薄膜微结构及电学性质的影响.发现厚度20纳米以内的锐钛矿相结晶TiO2过渡层可使BST薄膜由无规则取向转变为(111)择优取向,而非晶和较厚TiO2过渡层对BST薄膜的取向无影响.结晶的TiO2过渡层也使薄膜的表面颗粒变细.还研究了不同厚度TiO2对BST薄膜电学性质的影响,结果表明BST薄膜在Pt(111)底电极上加入极薄的结晶TiO2过渡层后电学性质有明显改善,薄膜的介电常数和可调谐度提高,而介电损耗降低.加入膜厚约5nm的TiO2过渡层后,测试频率为10 kHz时薄膜相应介电常数、介电损耗及可调谐度分别为513、0.053和36.7%.     

Electrospun PHBV/PEO co-solution blends: Microstructure,thermal and mechanical properties

Blending allows to tailor and modulate the properties of selected polymers. Blends of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polyethylene oxide (PEO) were fabricated by electrospinning in different weight ratios i.e. 100:0, 80:20, 70:30, 50:50, 0:100.In order to evaluate the influence of PEO addition on the final properties of PHBV, a complete microstructural, thermal and mechanical characterization of PHBV/PEO blends has been performed. The two neat polymeric membranes were also considered for the sake of comparison. The following characterization techniques were employed: scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy, simultaneous thermogravimetric and differential analyses (TG-DTA), differential scanning calorimetry (DSC), and uniaxial tensile tests.All electrospun mats consisted of randomly oriented and uniform fibers. It has been observed that the microstructure of PHBV/PEO was remarkably affected by blend composition. The average fiber size ranged between 0.5 μm and 2.6 μm. It resulted that the electrospun polymeric blends consisted of separate crystalline domains associated to an amorphous interdisperse phase. PHBV/PEO blends presented intermediate mechanical properties, in terms of tensile modulus and ultimate tensile stress, with respect to the two neat components.     

Ionic transport in P(VdF-HFP)-PEO based novel microporous polymer electrolytes

A novel microporous polymer electrolyte (MPE) comprising blends of poly(vinylidene fluoride-cohexafluoropropylene) [P(VdF-HFP)] and polyethylene oxide (PEO) was prepared by phase inversion technique. It was observed that addition of PEO improved the pore configuration, such as pore size, pore connectivity and porosity of P(VdF-HFP) based membranes. The room temperature ionic conductivity was significantly enhanced. The highest porosity of about 65% and ionic conductivity of about 7 × 10⁻⁴ S cm⁻¹ was obtained when the weight ratio of PEO was 40%. The liquid electrolyte uptake was found to increase with increase in porosity and pore size. However, at higher weight ratio of PEO (> 40%) porosity, pore size and ionic conductivity was decreased. This descending trend with further increase of PEO weight ratio was attributed to conglomeration effect of PEO at the pores.     

Nanodomain development of semifluorinated diblock copolymeric thin films via solvent vapor annealing

The effect of solvent vapor annealing on the morphological change of poly(ethylene oxide)-b-poly(1H,1H dihydrofluorooctyl methacrylate) (PEO-b-PFOMA) micellar thin films has been studied. The time development of the nanodomain structure in PEO(5k)-b-PFOMA(10k) thin films was investigated with the vapor treatment of perfluoroalkanes. The block copolymeric thin film was initially cast from chloroform which is a good solvent for PEO. The as-cast film which has disordered morphology can be changed to ordered cylindrical morphology and at last to highly ordered morphology consisting of PEO spherical domains and PFOMA continuous phase by varying the annealing time.     

Ordered nanostructure of PS-b-PEO copolymer by solvent annealing with mixture of benzene/water vapor and its micropattern fabrication

We investigate the effect of water/benzene co-solvent vapor on the ordering of poly(styrene-b-ethylene oxide) (PS-b-PEO) copolymer thin film on silicon substrate upon solvent annealing. In-plane cylindrical PEO microdomains were observed after exposure of benzene vapor. The addition of water vapor dominantly produced the cylindrical PEO domains aligned perpendicular to the substrate. The best ordering of the cylinders was obtained at the water fraction of approximately 0.05. The degree of ordering decreases while the periodicity of haxagonally packed PEO cylinders increases with the amount of water in the vapor mixture. The average center-to-center distance of hexagonally packed cylindrical PEO microdomains increases with the water fraction from approximately 25 nm to 40 nm. As one way of utilizing the dewetting of thin films inevitable during solvent annealing, PS-b-PEO micropatterns prepared by microcontact printing were treated with co-solvent vapor, which allows us to fabricate the controlled dewet structures guided by the micropatterns. Cylinder-to-sphere phase transition of PEO microdomains also occurred upon solvent annealing in the micropatterned PS-b-PEO films.     

Orientation-dependent phase separation of GaAsSb epilayers grown by gas-source molecular-beam epitaxy

This work describes a regular solution model that considers the free energy of the surface monolayer to explain the orientation-dependent phase separation in GaAsSb. In the proposed model, only the interaction between the second nearest-neighboring atoms sitting on the same monolayer contributes to the interaction parameter. Consequently, the parameter reduces to Ω/2 and Ω/3 for (111)B GaAsSb and (100) GaAsSb, where Ω denotes the parameter of bulk GaAsSb. By including the strain effect, the proposed model thoroughly elucidates the immiscibility behavior of (111)B GaAsSb and (100) GaAsSb.     

Local thermal-mechanical analysis of ultrathin interfacially mixed poly(ethylene oxide)/poly(acrylic acid) layer-by-layer electrolyte assemblies

Ion conductivities of layer-by-layer (LBL) assemblies of solid thin film polyelectrolyte systems involving poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) were found to be a strong function of the number of bilayer stacks, n, with conductivities approaching 10^− 7 S/cm for n < 10, compared to 10^− 9 S/cm for n ≥ 10 and 10^− 10 S/cm for bulk PEO. Increased ion conductivity for low LBL stack numbers (n < 10) originated to part from an effective suppression of the PEO crystallization via PEO/PAA blending, which could be inferred from local glass transition temperature measurements involving shear modulation force microscopy. Another phenomenon responsible for high conductivity in thin films was found in the in-plane phase heterogeneity of PEO and PAA. Increased ion conductivity for larger LBL stacks (n ≥ 10) were attributed to low concentration autoblending caused by PEO-PAA hydrogen bonding, and an average layer thickness of noticeably less than 100 nm. The effect of interfacial constraints was evident in the degree of intermixing, addressed by a thin film extended Fox blend analysis, in the glass and melting transitions of PEO and PAA pure film components. While the glass transition value of PAA decreased by 55% to 46 °C for an 8 nm film, the melting transition for PEO decreased by 15% to 64 °C caused by surface tension effects.