Free energy calculations of small molecules in dense amorphous polymers. Effect on the initial guess configuration in molecular dynamics studies

The excess free energy of small molecules in the amorphous polymers poly(ethylene) and poly(dimethylsiloxane) was calculated, using the test-particle-insertion method. The method was applied to polymer configurations obtained from molecular dynamics simulations with differently prepared initial guess configurations. It was found that the calculated solubility coefficients strongly depend on the quality of the initial guess configuration. Slow compression of dilute systems, during which process only the repulsive parts of the nonbonded Lennard-Jones potentials are taken into account, yields polymer melts which are better relaxed, and which offer lower solubilities for guest molecules compared with polymer melts generated at the experimental density or prepared by compressing boxes with soft-core nonbonded potentials. For the last two methods initial stresses relax by straining the internal modes (bond angles, torsion angles) of the chain

Novel thin film polymer foaming technique for low and ultra low-k dielectrics

The results presented show a novel route for the preparation of thin ultra-low-k polymer films based on commercial and "non-exotic" (non-expensive) polyimide by a foaming technique. Dependent on the glass transition temperature of the polyimide mechanically and thermally stable (> 300 °C) films having porosities of ca. 40 % and k-values below 2.0 are formed. A further reduction into the ultra low k region may be accomplished by tailoring the shape of the pores from spherical into disc-like void

Supported liquid membranes modification with sulphonated poly(ether ether ketone). Permeability, selectivity and stability

The development of a new type of composite membrane consisting of a microfiltration support membrane, an immobilised liquid membrane phase and a hydrophilic, charged polymer layer and its function as a supported liquid membrane (SLM) for copper selective transport are described. The ion-exchange layers function as stabilisation layers to improve the membrane lifetime and consist of sulphonated poly(ether ether ketone) (SPEEK). This polymer shows a high permeability for copper ions due to the presence of fixed negative charges and to its swelling capacity in an aqueous phase. A method was developed to prepare composite membranes composed of the support membranes Celgard with one stabilisation layer on either the feed or strip side of the membrane or on both sides. Good adhesion of homogeneous, negatively charged, hydrophilic SPEEK layers to the hydrophobic macroporous support membranes could only be established when the support membranes were first hydrophilised with a concentrated sulphuric acid solution containing 5 wt% free SO3. The lifetime of the SLMs is significantly improved when one stabilisation layer is applied at the strip side or two layers at both sides of the SLM. A second advantage of this composite SLM is the increase in copper flux caused by a decrease in thickness of liquid membrane phase. However, when SPEEK penetrates entirely through some pores of the support membrane, ions diffuse non-specifically through the SPEEK matrix resulting in an undesired selectivity loss. This phenomenon occurs only when thin Celgard membranes are used as support membranes

Highly permeable and mechanically robust silicon carbide hollow fiber membranes

Silicon carbide (SiC) membranes have shown large potential for applications in water treatment. Being able to make these membranes in a hollow fiber geometry allows for higher surface-to-volume ratios. In this study, we present a thermal treatment procedure that is tuned to produce porous silicon carbide hollow fiber membranes with sufficient mechanical strength. Thermal treatments up to 1500 °C in either nitrogen or argon resulted in relatively strong fibers, that were still contaminated with residual carbon from the polymer binder. After treatment at a higher temperature of 1790 °C, the mechanical strength had decreased as a result of carbon removal, but after treatments at even higher temperature of 2075 °C the SiC-particles sinter together, resulting in fibers with mechanical strengths of 30–40 MPa and exceptionally high water permeabilities of 50,000 L m−2 h−1 bar−1. Combined with the unique chemical and thermal resistance of silicon carbide, these properties make the fibers suitable microfiltration membranes or as a membrane support for application under demanding condition

An Organic Metal/Silver Nanoparticle Finish on Copper for Efficient Passivation and Solderability Preservation

For the first time, a complex formed by polyaniline (in its organic metal form) and silver has been deposited on copper in nanoparticulate form. When depositing on Cu pads of printed circuit boards it efficiently protects against oxidation and preserves its solderability. The deposited layer has a thickness of only nominally 50 nm, containing the Organic Metal (conductive polymer), polyaniline, and silver. With >90% (by volume), polyaniline (PAni) is the major component of the deposited layer, Ag is present equivalent to a 4 nm thickness. The Pani–Ag complex is deposited on Cu in form of about 100 nm small particles. Morphology, electrochemical characteristics, anti-oxidation and solderability results are reported

3D Nanofabrication inside rapid prototyped microfluidic channels showcased by wet-spinning of single micrometre fibres

Microfluidics is an established multidisciplinary research domain with widespread applications in the fields of medicine, biotechnology and engineering. Conventional production methods of microfluidic chips have been limited to planar structures, preventing the exploitation of truly three-dimensional architectures for applications such as multi-phase droplet preparation or wet-phase fibre spinning. Here the challenge of nanofabrication inside a microfluidic chip is tackled for the showcase of a spider-inspired spinneret. Multiphoton lithography, an additive manufacturing method, was used to produce free-form microfluidic masters, subsequently replicated by soft lithography. Into the resulting microfluidic device, a threedimensional spider-inspired spinneret was directly fabricated in-chip via multiphoton lithography. Applying this unprecedented fabrication strategy, the to date smallest printed spinneret nozzle is produced. This spinneret resides tightly sealed, connecting it to the macroscopic world. Its functionality is demonstrated by wet-spinning of single-digit micron fibres through a polyacrylonitrile coagulation process induced by a water sheath layer. The methodology developed here demonstrates fabrication strategies to interface complex architectures into classical microfluidic platforms. Using multiphoton lithography for in-chip fabrication adopts a high spatial resolution technology for improving geometry and thus flow control inside microfluidic chips. The showcased fabrication methodology is generic and will be applicable to multiple challenges in fluid control and beyond

Mitigating Water Crossover by Crosslinked Coating of Cation‐Exchange Membranes for Brine Concentration

Undesired water crossover through ion-exchange membranes is a significant limitation in electrically driven desalination processes. The effect of mitigating water crossover is twofold: 1) The desalination degree is less reduced due to the unwanted removal of water, and 2) the brine concentration is increased due to decreased dilution by an unwanted crossover of water molecules. Hence, water crossover limits the desalination and concentration efficiency of the processes, while the energy demand to achieve a certain level of desalination or concentration increases. This effect is especially pronounced when treating high salinity solutions, which goes hand in hand with the crossover of many ions through the ion-exchange membranes. A crosslinked coating for cation-exchange membranes (CEMs) is presented in this work, which can significantly mitigate such undesired water crossover. The efficacy is demonstrated using the flow-electrode capacitive deionization process applied for desalination and concentration of saline brines at feed concentrations of 60 and 120 g L−1 NaCl. With just a single coated CEM, the water crossover was reduced by up to 54%

Dynamics of the spontaneous breakdown of superhydrophobicity

Drops deposited on rough and hydrophobic surfaces can stay suspended with gas pockets underneath the liquid, then showing very low hydrodynamic resistance. When this superhydrophobic state breaks down, the subsequent wetting process can show different dynamical properties. A suitable choice of the geometry can make the wetting front propagate in a stepwise manner leading to {\it square-shaped} wetted area: the front propagation is slow and the patterned surface fills by rows through a {\it zipping} mechanism. The multiple time scale scenario of this wetting process is experimentally characterized and compared to numerical simulations.Comment: 7 pages, 5 figure

Tracking homogeneous reactions during electrodialysis of organic acids via EIS

[EN] Organic acids are highly valuable platform chemicals that can be obtained from bioresources and subsequently transformed into a wide spectrum of profitable consumer goods. After their synthesis, organic acids need to be separated from other by-products and conveniently upconcentrated. Based on the ionic nature of organic acids, electromembrane processes are viable technologies for their recovery. Transport of weak acids through ion- exchange membranes is a complex process influenced by multiple phenomena, i.e. concentration polarization, water dissociation and counterion-membrane interactions. In the present study, the transport of two different organic acids (citric and oxalic acid) through anion-exchange membranes is investigated by means of using linear sweep voltammetry, chronopotentiometry and electrochemical impedance spectroscopy (EIS). Results have shown that, at pH values where multivalent acid anions predominate in solution, a first limiting current density is registered in the current-voltage curves, followed by an increase in membrane resistance. A further increase in current leads to a second limiting current density and a steeper increase in membrane resistance associated with an intensified ion depletion. A strong correlation between polarization curves and electrochemical impedance measurements reveals that such increase in resistance is prompted by generation of Hþ and OH? ions and the concomitant onset of homogeneous reactions in very thin solution layers. The generation of Hþ and OH? ions is tracked by a Gerischer arc in the impedance spectra. As the polarization level increases, the subsequent reaction of multivalent anions into lower-charge acid anions involves the evolution of additional Gerischer arcs. Furthermore, the lower conductivity of the reaction products correlates with the increased system resistance. The characteristic times of these reactions are in the order of milliseconds, thus being only directly accessible with the use of frequency response analysis techniques, such as EIS.M.C. Marti-Calatayud acknowledges the support of Generalitat Valenciana through the funding APOSTD/2017/059.Martí Calatayud, MC.; Evdochenko, E.; Bär, J.; García Gabaldón, M.; Wessling, M.; Pérez-Herranz, V. (2020). Tracking homogeneous reactions during electrodialysis of organic acids via EIS. Journal of Membrane Science. 595:1-10. https://doi.org/10.1016/j.memsci.2019.117592S110595Kiss, A. A., Lange, J.-P., Schuur, B., Brilman, D. W. F., van der Ham, A. G. J., & Kersten, S. R. A. (2016). Separation technology–Making a difference in biorefineries. Biomass and Bioenergy, 95, 296-309. doi:10.1016/j.biombioe.2016.05.021Abels, C., Carstensen, F., & Wessling, M. (2013). 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Current-voltage characteristic of anion-exchange membrane in monosodium phosphate solution. Modelling and experiment. Journal of Membrane Science, 542, 177-185. doi:10.1016/j.memsci.2017.08.002Martí-Calatayud, M., García-Gabaldón, M., & Pérez-Herranz, V. (2018). Mass Transfer Phenomena during Electrodialysis of Multivalent Ions: Chemical Equilibria and Overlimiting Currents. Applied Sciences, 8(9), 1566. doi:10.3390/app8091566Melnikova, E. D., Pismenskaya, N. D., Bazinet, L., Mikhaylin, S., & Nikonenko, V. V. (2018). Effect of ampholyte nature on current-voltage characteristic of anion-exchange membrane. Electrochimica Acta, 285, 185-191. doi:10.1016/j.electacta.2018.07.186Femmer, R., Mani, A., & Wessling, M. (2015). Ion transport through electrolyte/polyelectrolyte multi-layers. Scientific Reports, 5(1). doi:10.1038/srep11583Belloň, T., Polezhaev, P., Vobecká, L., Svoboda, M., & Slouka, Z. (2019). 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Optimized pH and Its Control Strategy Lead to Enhanced Itaconic Acid Fermentation by Aspergillus terreus on Glucose Substrate. Fermentation, 5(2), 31. doi:10.3390/fermentation5020031Martí-Calatayud, M. C., García-Gabaldón, M., & Pérez-Herranz, V. (2012). Study of the effects of the applied current regime and the concentration of chromic acid on the transport of Ni2+ ions through Nafion 117 membranes. Journal of Membrane Science, 392-393, 137-149. doi:10.1016/j.memsci.2011.12.012Martí-Calatayud, M. C., García-Gabaldón, M., & Pérez-Herranz, V. (2013). Effect of the equilibria of multivalent metal sulfates on the transport through cation-exchange membranes at different current regimes. Journal of Membrane Science, 443, 181-192. doi:10.1016/j.memsci.2013.04.058Butylskii, D. Y., Mareev, S. A., Pismenskaya, N. D., Apel, P. Y., Polezhaeva, O. A., & Nikonenko, V. V. (2018). Phenomenon of two transition times in chronopotentiometry of electrically inhomogeneous ion exchange membranes. 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