Systematic characterization of degraded anion exchange membranes retrieved from vanadium redox flow battery field tests

Commercially available anion exchange membranes were retrieved from VRFB field tests and their degradation due to the various operation conditions is analyzed by in-situ and ex-situ measurements. Ion exchange capacity, permeability and swelling power are used as direct criteria for irreversible changes. Small-angle X-ray scattering (SAXS) and Differential scanning calorimetry (DSC) analyses are used as fingerprint methods and provide information about the morphology and change of the structural properties. A decrease in crystallinity can be detected due to membrane degradation, and, in addition, an indication of reduced polymer chain length is found. While the proton diffusion either increase or decline significantly, the ion exchange capacity and swelling power both are reduced. The observed extent of changes was in good agreement with in-situ measurements in a test cell, where the coulombic and voltage efficiencies are reduced compared to a pristine reference material due to the degradation process

Reactive block copolymers for patterned surface immobilization with sub-30 nm spacing

Phase-segregating block copolymers are powerful platforms for nanofabrication, particularly when employed as lithographic mask precursors. Surface-reactive polymeric films with distinct sub-30 nm domains are also proposed as covalent docking platforms for scalable, high-resolution molecular patterned immobilization. Here, the well-known self-assembling polystyrene-block-polyisoprene system is the starting point to produce a small library of derivatives with distinct reactive pendant groups (halide, azide, pentafluorophenylalkyl) by nitroxide-mediated radical polymerization. We find that controlling film thickness is crucial to obtain a perpendicular lamellar morphology and that the presence of the functional groups has a limited impact on self-assembly, yet may influence characteristic domain dimensions. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM) are utilized in concert to assess the phase behavior of the polymers and the surface features of the nanostructures. As a proof-of-concept for the surface reactivity, click chemistry-driven immobilization of a model water-soluble polymer is evidenced by X-ray photoelectron spectroscopy (XPS) and preservation of the underlying morphology is investigated by AFM

Stability of star-shaped RAFT polystyrenes under mechanical and thermal stress

Well-defined three-arm and four-arm star polymers designed via a Z-group approach carrying trithiocarbonate functionalities at the core are prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization featuring molecular weights of Mn{,}SEC = 156 kDa{,} D = 1.16 (3-arm) and Mn{,}SEC = 162 kDa{,} D = 1.15 (4-arm) based on multi-angle laser light scattering (MALLS) detection{,} respectively. The star-shaped polystyrenes are subjected (in bulk) to thermal stress in the temperature range between 140 and 200 [degree]C from 10 minutes up to 96 h. The thermally treated 3-arm and 4-arm star polymers are analyzed via size exclusion chromatography (SEC) to quantify the degradation process at variable temperatures as a function of time under an argon atmosphere. Cleavage rate coefficients of the star polymers are deduced as a function of temperature{,} resulting in activation parameters for the cleavage process{,} i.e. Ea = 131 kJ mol-1; A = 3.93 [times] 1011 s-1 (Mn{,}SEC = 156 kDa{,} D = 1.16{,} 3-arm star) and Ea{,} = 134 kJ mol-1; A = 9.13 [times] 1011 s-1 (Mn{,}SEC = 162 kDa{,} D = 1.15{,} 4-arm star){,} respectively. Processing of the star-shaped polymers is mimicked via a small scale counter rotating twin screw extrusion to achieve nonlinear shear and elongation flow under pressure. Furthermore{,} a rheological assessment via the linear shear deformation region (small amplitude oscillatory shear{,} SAOS) allows for a correlation of the processing conditions with the thermal degradation properties of the star polymers in the melt. Zero shear viscosity ([small eta]0) as a criterion of the degradation process is measured in the rheometer and correlated to the weight-average molecular weight{,} Mw

Modeling Interaction-Oriented Architectures using Choreographies

The Software architecture of a system can be regarded as a consistent set of views to describe the system. This paper focuses on the interaction between components in a system. These can be modeled as choreographies, capturing all allowed interactions between the components. In this paper, we show that it is feasible to analyze a composed set of these choreographies: a tree of choreographies in which each member may refer to another. The two major components of the analysis are correctness by structure: a choreography needs to follow strict rules to guarantee soundness. Otherwise, the choreography is transformed into a Petri net which is checked by an external tool. This paper shows the theoretical techniques to verify a composed choreography, and implements the solutions into a single educational modeler tool: INORA2

Mechano-Optical Characterization of Extrusion Flow Instabilities in Styrene-Butadiene Rubbers: Investigating the Influence of Molecular Properties and Die Geometry

The extrusion flow instabilities of two commercial styrene‐butadiene rubbers are investigated as they vary in isomer content (1,4‐cis, 1,4‐trans, and 1,2 conformation) of the butadiene monomer and the molecular architecture (linear, branched). The investigated samples have similar multimodal molecular weight distribution. Two geometries of extrusion dies, slit and round capillary, are compared in terms of the type and the spatial characteristics of the flow instabilities. The latter are quantified using three methods: a highly pressure sensitive slit die, online and offline optical analysis. The highly pressure‐sensitive slit die has three piezoelectric pressure transducers (Δt ≈ 10$^{-3}$ s and Δp ≈ 10$^{-5}$ bar) placed along the die length. The characteristic frequency (f$_{Char.}$) of the flow instabilities follows a power law behavior as a function of shear rate to a 0.5 power for both materials,  $_{ℎ.}$∝$^{˙0.5}$$_{app.}$. A qualitative model is used to predict the spatial characteristic wavelength (λ) of the flow instabilities from round capillary to slit dies and vice versa. Slip velocities (V$_{s}$) are used to quantify the slippage at slit and round capillary dies as well

BMP receptor inhibition enhances tissue repair in endoglin heterozygous mice

Hereditary hemorrhagic telangiectasia type 1 (HHT1) is a severe vascular disorder caused by mutations in the TGF beta/BMP co-receptor endoglin. Endoglin haploinsufficiency results in vascular malformations and impaired neoangiogenesis. Furthermore, HHT1 patients display an impaired immune response. To date it is not fully understood how endoglin haploinsufficient immune cells contribute to HHT1 pathology. Therefore, we investigated the immune response during tissue repair in Eng+/- mice, a model for HHT1. Eng+/- mice exhibited prolonged infiltration of macrophages after experimentally induced myocardial infarction. Moreover, there was an increased number of inflammatory M1-like macrophages (Ly6C(high)/CD206(-)) at the expense of reparative M2-like macrophages (Ly6C(low)/CD206(+)). Interestingly, HHT1 patients also showed an increased number of inflammatory macrophages. In vitro analysis revealed that TGF beta-induced differentiation of Eng+/- monocytes into M2-like macrophages was blunted. Inhibiting BMP signaling by treating monocytes with LDN-193189 normalized their differentiation. Finally, LDN treatment improved heart function after MI and enhanced vascularization in both wild type and Eng+/- mice. The beneficial effect of LDN was also observed in the hind limb ischemia model. While blood flow recovery was hampered in vehicle-treated animals, LDN treatment improved tissue perfusion recovery in Eng+/- mice. In conclusion, BMPR kinase inhibition restored HHT1 macrophage imbalance in vitro and improved tissue repair after ischemic injury in Eng+/- mice.Therapeutic cell differentiatio

Coupling of Rotational Motion with Shape Fluctuations of Core-shell Microgels Having Tunable Softness

The influence of shape fluctuations on deformable thermosensitive microgels in aqueous solution is investigated by dynamic light scattering (DLS) and depolarized dynamic light scattering (DDLS). The systems under study consist of a solid core of polystyrene and a thermosensitive shell of cross-linked poly(N-isopropylacrylamide) (PNIPA) without and with embedded palladium nanoparticles. PNIPA is soluble in water, but has a lower critical solution temperature at 32 C (LCST). Below the LCST the PNIPA shell is swollen. Here we find that besides translational and rotational diffusion, the particles exhibit additional dynamics resulting from shape fluctuations. This leads to a pronounced apparent increase of the rotational diffusion coefficient. Above the transition temperature the shell collapses and provides a rather tight envelope of the core. In this state the dynamics of the shell is frozen and the core-shell particles behave like hard spheres. A simple physical model is presented to capture and explain the essentials of the coupling of rotational motion and shape fluctuations.Comment: 9 pages, 7 figure

Modeling of Intermediate Structures and Chain Conformation in Silica-Latex Nanocomposites Observed by SANS During Annealing

The evolution of the polymer structure during nanocomposite formation and annealing of silica-latex nanocomposites is studied using contrast-variation small angle neutron scattering. The experimental system is made of silica nanoparticles (Rsi \approx 8 nm) and a mixture of purpose-synthesized hydrogenated and deuterated nanolatex (Rlatex \approx 12.5 nm). The progressive disappearance of the latex beads by chain interdiffusion and release in the nanocomposites is analyzed quantitatively with a model for the scattered intensity of hairy latex beads and an RPA description of the free chains. In silica-free matrices and nanocomposites of low silica content (7%v), the annealing procedure over weeks at up to Tg + 85 K results in a molecular dispersion of chains, the radius of gyration of which is reported. At higher silica content (20%v), chain interdiffusion seems to be slowed down on time-scales of weeks, reaching a molecular dispersion only at the strongest annealing. Chain radii of gyration are found to be unaffected by the presence of the silica filler