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Cation exchange membranes (CEMs) are widely used for water desalination, as well as for the separation and concentration of alkali by electrodialysis (ED). The economic viability of the process depends on the electrochemical properties of the CEM. Sulfonated poly(ether ether ketone) (SPEEK) has been chosen to fabricate the CEM using the dry wet phase inversion (DWPI) technique. DWPI requires less polymer material and time, providing good mechanical strength due to the fabric support. DWPI can be a better alternative for crafting efficient dense membranes than solvent evaporation. Representative SPK/dd-PI/2 membrane prepared using a mixed solvent system of N, N dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (VDMF/VDMSO= 60:40) on both sides of the fabric exhibits superior desalination performance with a power consumption of 0.92 kW h kg–1and a current efficiency of >95% at an applied potential of 6 V using ED. It also shows better alkali recovery performance separately by diffusion dialysis (DD) (18.6%) and ED (79.2%). The alkali recovery performance was further enhanced to 94.6% by the hybrid DD-ED process. The counterionic transport phenomenon of Na+and the co-ionic transport of Cl–and OH–have been studied. The osmosis and electro-osmosis during the ED-based ion separation have also been investigated and compared with a commercial IONSEP-HC-C membrane and CEM prepared by a solvent evaporation technique from the SPEEK polymer.

Byline: Mohammad. Hashmi, Nazrul. Haque, Argha. Chatterjee, Suparna. Guha Langerhans cell histiocytosis (LCH) is a relatively rare disease affecting the reticuloendothelial system in the pediatric age group. It can affect [...]

Electron spin resonance spectroscopy revealed that some free radicals were trapped in the precipitated polymer during the precipitation polymerization of acrylamide conducted in nonsolvents of the polymer [t-butyl alcohol (TBA), acetone and methanol]. The trapped radical concentration decreased with an increase in the chain-transfer activity of the aforementioned liquids. A 100% polymerized acrylamide in TBA prepared with a 10% monomer concentration and a 3 × 10⁻³ mol/dm³ azobisisobutyronitrile concentration at 50 °C contained approximately 2 radicals per 100 polymer molecules. The trapped radicals on exposure to air decayed with time according to second-order kinetics. The rate constant was evaluated and found to be in reasonably good agreement with the rate constant evaluated from data published long ago for the decay of trapped polyacrylonitrile radicals following their exposure to air. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1192–1197, 2003

Polyacrylamide prepared by dispersion (precipitation) polymerization in an aqueous t-butyl alcohol (TBA) medium is only partially soluble when the TBA concentrations in the polymerization media are in the range 82 vol % < TBA < 95 vol %. Independent experiments with a soluble (linear) sample of polyacrylamide show that the polymer swells sufficiently in the aforementioned media to lower the glass-transition temperature of the polymer below the polymerization temperature (50 °C). The anomalous solubility has been attributed to the crosslinking of polymer chains that occurs during the solid-phase polymerization of acrylamide in the swollen polymer particles. It is postulated that some of the radical centers shift from the chain end to the chain backbone during solid-phase polymerization by chain transfer to neighboring polymer molecules, and when pairs of such radicals come into close vicinity, crosslinking occurs. However, dispersion (precipitation) polymerization in other media such as aqueous methanol and aqueous acetone yields polymers that are soluble. This result has been attributed to the fact that the polymer radical undergoes a chain-transfer reaction with these solvents at a much faster rate than with TBA, which overcomes the effect of the polymer-transfer reaction. Even the addition of as little as 5% methanol to a TBA–water mixture (TBA:water = 85:10) gives rise to a soluble polymer. The chain-transfer constants for acetone, methanol, and TBA have been determined to be 9.0 × 10⁻⁶, 6.9 × 10⁻⁶, and 1.48 × 10⁻⁶, respectively, at 50 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3434–3442, 2001

Bardet–Biedl syndrome (BBS) is an autosomal recessive, heterogenous disorder with a wide variety of clinical presentations. Although minor associations with type 2 diabetes mellitus have been reported, the association of type 1 diabetes mellitus with BBS is an extremely uncommon occurrence.