Layer-by-layer assembly of viral nanoparticles and polyelectrolytes: the film architecture is different for spheres versus rods

The development of tuneable thin film assemblies that contain (bio)nanoparticles is an emerging field in nanobiosciences/nanotechnology. Our research focuses on the utilisation of viral nanoparticles (VNPs) as tools and building blocks for materials science. In previous reports we studied multilayered arrays of chemically modified cowpea mosaic virus (CPMV) particles and linker molecules. To extend these studies and to gain more insights into the architecture of the arrays, we report here on the construction of multilayered assemblies of native plant viral particles and polyelectrolytes. We specifically addressed the question of whether the shape of the VNPs influences the overall structures of the arrays. To study this, we have chosen two particles with similar surface properties but different shapes: CPMV was used as a sphere-like VNP, and tobacco mosaic virus (TMV) served as a rod-shaped VNP. The multilayers were self-assembled on solid supports through electrostatic interactions. Multilayer build-up was followed by quartz crystal microbalance with dissipation monitoring and UV/Vis spectroscopy. Scanning electron microscopy was used to characterize the topologies of the thin films. Our studies show that shape indeed matters. Incorporation of CPMV in alternating arrays of VNPs and polyelectrolytes is demonstrated; in stark contrast, TMV particles were found to be excluded from the arrays, and floated atop the architecture in an ordered structure.     

Acrylamide‐based anionic polyelectrolytes and their applications: A survey

Water‐soluble polymers are found in a very broad range of industrial applications. An important class of these is acrylamide‐based polymers which bear negative charges along the polymer chain and are called anionic polyelectrolytes. These negatively charged polymers are widely used as flocculants, rheology control agents, and adhesives. They are employed especially in oil field operations as viscosity control agents for enhanced oil recovery and to a lesser degree in engineering fluids used for lubrication, for effluent reclaiming, and for opening oil passage channels in oil‐bearing rock. Paper manufacture, mining, and water treatment processes also benefit from the use of acrylamide‐based polymers to flocculate solids in aqueous dispersions. The acrylamide‐based polymers are made by the free‐radical polymerization of acrylamide and its derivatives via bulk, solution, precipitation, suspension, emulsion, and copolymerization techniques. Among these, solution polymerization is a preferred technique because of difficulty with temperature and agitation control in bulk polymerization and the cost of surfactants and solvents for suspension, emulsion, and precipitation polymerization. The anionic polymers may interact with particles in aqueous dispersions in several ways that result in the stability or instability of the dispersions. The particles in solid‐liquid phases can be destabilized through three main mechanisms which promote flocculation and cause destabilization. These mechanisms are polymer bridging, charge neutralization, and polymer adsorption. The particles in solid‐liquid phases can be stabilized by the anionic polymers through both electrostatic and steric repulsive forces. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Phosphorescent chelating polyelectrolytes and their neutral precursors: Synthesis, characterizations, photoluminescence and electroluminescence

Novel chelating polyfluorene polyelectrolytes and their corresponding neutral precursors with Ir complex incorporated into polymer backbone were synthesized by Suzuki polycondensation reaction. The aminoalkyl or quaternized ammonium group provides good solubility of these phosphorescent polymers in alcohols which has a great advantage in fabrication of multi-layer polymer phosphorescent PLEDs. The photophysical and electroluminescent properties of the phosphorescent polyelectrolytes and their neutral precursors were investigated. The phosphorescent emission bands from both polyelectrolytes and neutral polymers which lie at around 640 nm displayed a saturated red emission. Devices fabricated from these phosphorescent polymers with air-stable high work function metals, such as Al, as cathode showed comparable device performance with low work function metals, such as Ba.     

Layer-by-layer deposition of shortened nanotubes or polyethylene glycol-derivatized nanotubes on liposomes: A tool for increasing liposome stability

A simple strategy for preparing potential drug delivery systems is presented which appears to be a good alternative to stealth liposomes in terms of stability in buffered aqueous solutions. Microcapsules have been prepared by deposition of shortened and polyethylene glycol-derivatized nanotubes onto positively charged multilamellar vesicles using the layer-by-layer technique. The stability of microcapsules has been determined turbidimetrically by measuring the rate of microcapsule breakdown induced by addition of a destabilizing agent such as the nonionic surfactant octaethyleneglycol mono-n-dodecyl ether. The investigated microcapsules have proven to be more stable than both pure liposomes and stealth liposomes.     

Polymeric ionic liquids: Broadening the properties and applications of polyelectrolytes

The introduction of new ionic moieties, cations and anions, is extending the properties and classical applications of polyelectrolytes. These new polyelectrolytes are being named polymeric ionic liquids (PILs) in analogy to their monomeric constituents (i.e. cations such as imidazolium, pyridinium, pyrrolidonium and anions such as hexafluorophosphate, triflates, amidotriflates). This is giving rise to a new family of functional polymers with particular properties and new applications. The first part of this review will focus on the synthetic aspects of PILs and the main aspects related to their physico-chemical properties. In the second part we will review the new technological applications of these polymers such as polymer electrolytes in electrochemical devices, building blocks in materials science, nanocomposites, gas membranes, innovative anion sensitive materials, smart surfaces, and a countless set of applications in different fields such as energy, environment, optoelectronics, analytical chemistry, biotechnology or catalysis.     

Chemical vapor deposition of aluminum for ulsi applications

Aluminum has been used widely as a conducting material in the fabrication of integrated circuits, and chemical vapor deposition process for Al has been actively investigated for the application in ultra large scale integration. In this review, various precursors, mainly alkyl aluminum and alane compounds, and reaction mechanisms of these precursors in Al CVI) are described. Epitaxial growth and selectivity of the deposition are also discussed. In addition to thermal reactions, plasma and photochemical reactions are also briefly described.     

Electrophoretic deposition of ceramic materials for fuel cell applications

La_0.8Sr_0.2Ga_0.875Mg_0.125O_3-x (LSGM), La_0.8Sr_0.2Co_0.2Fe_0.8O_3-δ (LSCF), yttria stabilized zirconia (YSZ) and (Ce_0.8Gd_0.2)O_1.9 (CGO) were electrophoretically deposited on Ni foils and Ni-yttria stabilized zirconia substrates prepared by tape casting. It was demonstrated that the ethyl alcohol–phosphate ester–polyvinyl butyral system is an effective solvent–dispersant–binder system for electrophoretic deposition of these materials. The influence of dispersant, binder and current density on deposition efficiency and deposit morphology was studied. The microstructure of the deposits was examined by electron microscopy. The proposed solvent–dispersant–binder medium for electrophoretic deposition of LSGM, LSCF, YSZ and CGO has important advantages and implications in fuel cell design.     

Fused deposition processing polycaprolactone of composites for biomedical applications

The polycaprolactone (PCL)-engineered scaffolds demonstrate cell viability, which is useful for bone tissue applications. The FDA-approved PCL can be engineered with various transition metals, polymers, and nanomaterials, for biomimicking of extracellular matrix via fabrication of its scaffolds. Fused deposition modeling (FDM) is an innovative technique for processing of biopolymers via biologically functionalized nanoparticles, leveraging design of stacked architecture at microlevel resolution. Present review gives progress on PCL biomaterials processed via FDM, for bioactive scaffolds and bone tissue applications. Finally, review concludes with benefits of PCL biomaterials processed via FDM and their applicability for biomedical applications.     

Conjugated polyelectrolytes: A new class of semiconducting material for organic electronic devices

This feature article presents a short review of the recent developments in the synthesis of conjugated polyelectrolytes (CPEs) along with their applications in organic optoelectronic devices with particular focus on the molecular structures of CPEs with ionic functionality, synthetic approaches, and their utilization as an interfacial layer. The orthogonal solubility of the CPEs allows the simple preparation of multilayer organic devices by solution casting on top of a nonpolar organic photoactive layer without disturbing the interfaces, showing their effectiveness in tuning the electronic structures at the interfaces for improving the charge carrier transport and resulting device properties. These achievements highlight the dynamic nature of CPEs and their applicability to a wide range of optoelectronic devices.     

Electrophoretic deposition of macroporous carbon nanotube assemblies for electrochemical applications

Electrophoretic deposition of macroporous assemblies of single-walled carbon nanotubes (SWCNTs) is described. The macroporous structure was created thanks to the presence of polystyrene (PS) beads which were co-deposited with the carbon nanotubes in a 60 V potential field. The ratio between the quantity of carbon nanotubes and polystyrene beads in the solution for deposition was found to be critical for the proper self-assembly of the composite film during electrophoretic deposition. The macroporous films have been characterized by scanning electron microscopy, atomic force microscopy and profilometry. The macroporosity was revealed after template removal (calcination of the PS beads). Access to the internal surface was assessed by electrochemical characterization using methylene green as a redox probe likely to adsorb on the SWCNT surface. Platinum nanoparticles and a sol–gel layer with encapsulated dehydrogenase and NAD⁺ cofactor have been deposited on the macroporous SWCNT electrodes in order to illustrate the use of the macropore texture for the detection of H₂O₂ and for biosensor applications, respectively.     

Conductometric study of ion association in some polyelectrolytes

Conductances of sodium alginate, sodium carboxymethylcellulose and sodium carboxymethyl dextran solutions have been measured in the presence of sodium chloride. It has been found that the sum of the specific conductances of the components measured separately is always greater than the specific conductance of the mixture. The difference in specific conductance between the sum and the mixture, Δ, has been studied as a function of the polyelectrolyte concentration, concentration of sodium chloride and also temperature. An attempt has been made to interpret the results in terms of both electrostatic effects and the Donnan theory of membrane equilibrium. The latter approach does not seem satisfactory.     

Particle deposition in juvenile rat lungs: A model study

Lung development disruption in childhood due to air pollution is gaining growing attention. Although rats are widely used for studies of pulmonary toxicology, little is known about the fate of inhaled particles in juvenile rat lungs. We investigated detailed particle deposition in rat lungs at 15, 28, 40, and 81 days of age using a single path mathematical model. For normal breathing conditions, particles smaller than 0.1 μm deposited in extrathoracic airways more in juvenile rats compared to adults whereas alveolar deposition fraction for juvenile rats was smaller compared to adults for most particle sizes. Alveolar deposition per minute per unit body mass was appreciably lower for juvenile rats compared to adults and deposition per minute per unit area was lower for juvenile rats over the entire lungs for most particle sizes.     

Investigation of diamond deposition uniformity and quality for freestanding film and substrate applications

In this paper, we report on microwave CVD deposition of high quality polycrystalline diamond and on related post-processing steps to produce smooth, flat and uniformly thick films or diamond substrates. The deposition reactor is a 2.45 GHz microwave cavity applicator with the plasma confined inside a 12 cm diameter fused silica bell jar. The deposition substrates utilized are up to 75 mm diameter silicon wafers. The substrate holder is actively cooled with a water-cooled substrate holder to achieve a substrate surface temperature of 600–1150 C. The pressure utilized is 60–180 Torr and the microwave incident power is 2–4.5 kW. Important parameters for the deposition of thick films with uniform quality and thickness include substrate temperature uniformity as well as plasma discharge size and shape. As deposited thickness uniformities of ± 5% across 75 mm diameters are achieved with simultaneous growth rates of 1.9 μm/h. The addition of argon to the deposition gases improves film deposition uniformity without decreasing growth rate or film quality, over the range of parameters investigated. Post-processing includes laser cutting of the diamond to a desired shape, etching, lapping and polishing steps.     

Thin film silver deposition by electroplating for ULSI interconnect applications

Ag seed layers were pretreated with 1: 1,000 diluted nitric acid cleaning solution for 60 s to obtain a clean and oxide-free Ag surface. When an applied potential was less than ?800 mV in Ag electroplating, the deposition rate was over 2,000 Å/min and the resistivity of Ag deposit was 1.80 μΩ·cm. But the deposit film became rougher with a negative increase in the potential, and it was also observed through measuring the double layer capacitance. The resistivity of Ag film annealed at 350 °C for 30 min was decreased from 1.80 μΩ·cm to 1.67 μΩ·cm and the agglomeration of Ag grains was not observed on the surface of the annealed Ag films. To reduce the surface roughness, thiourea was added in the electrolyte and it was decreased below 15 nm.     

Stability improvement of CO2 foam for enhanced oil‐recovery applications using polyelectrolytes and polyelectrolyte complex nanoparticles

CO₂ foam for enhanced oil‐recovery applications has been traditionally used in order to address mobility‐control problems that occur during CO₂ flooding. However, the supercritical CO₂ foam generated by surfactant has a few shortcomings, such as loss of surfactant to the formation due to adsorption and lack of a stable front in the presence of crude oil. These problems arise because surfactants dynamically leave and enter the foam interface. We discuss the addition of polyelectrolytes and polyelectrolyte complex nanoparticles (PECNP) to the surfactant solution to stabilize the interface using electrostatic forces to generate stronger and longer‐lasting foams. An optimized ratio and pH of the polyelectrolytes was used to generate the nanoparticles. Thereafter we studied the interaction of the polyelectrolyte–surfactant CO₂ foam and the polyelectrolyte complex nanoparticle–surfactant CO₂ foam with crude oil in a high‐pressure, high‐temperature static view cell. The nanoparticle–surfactant CO₂ foam system was found to be more durable in the presence of crude oil. Understanding the rheology of the foam becomes crucial in determining the effect of shear on the viscosity of the foam. A high‐pressure, high‐temperature rheometer setup was used to shear the CO₂ foam for the three different systems, and the viscosity was measured with time. It was found that the viscosity of the CO₂ foams generated by these new systems of polyelectrolytes was slightly better than the surfactant‐generated CO₂ foams. Core‐flood experiments were conducted in the absence and presence of crude oil to understand the foam mobility and the oil recovered. The core‐flood experiments in the presence of crude oil show promising results for the CO₂ foams generated by nanoparticle–surfactant and polyelectrolyte–surfactant systems. This paper also reviews the extent of damage, if any, that could be caused by the injection of nanoparticles. It was observed that the PECNP–surfactant system produced 58.33% of the residual oil, while the surfactant system itself produced 47.6% of the residual oil in place. Most importantly, the PECNP system produced 9.1% of the oil left after the core was flooded with the surfactant foam system. This proves that the PECNP system was able to extract more oil from the core when the surfactant foam system was already injected. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44491.     

A spectroscopic study of polyamide fibres structurised with formaldehyde

Conclusions 1. A spectral study of the cross-linking of highly oridented Capron fibre with gaseous formaldehyde has been carried out.2. The formation of transverse chemical bonds in the form of methylene bridges has been shown.3. It has been established that the cross-linking process takes place at the unordered regions.All-Union Scientific Research Institute for Synthetic Fibres (VNIIV). Translated from Khimicheskie Volokna, No. 2, pp. 25–27, March–April, 1969.     

Electrophoretic deposition of polymers. II. Polyimides: A coulombic study

Quantitative studies on the electrophoretic deposition of a polyimide polymer were carried out over the voltage range 25–100 V dc. Deposition yield was related to voltage, time, and coulombs and was found to obey Faraday's laws of electrolysis. Equations relating yield to voltage and coulombs were obtained from the plotted data. Results of coulombic studies indicate that the effective equivalent weight of the polymeric species being deposited is between 6800 and 7500 (i.e., amount deposited per faraday). The coulombic yield is 75 mg per coulomb. Information and speculation on the size and composition of the electroactive species are presented.