Superhydrophobic electrospun POSS-PMMA copolymer fibres with highly ordered nanofibrillar and surface structures

A POSS-PMMA copolymer has been synthesised by conventional free-radical polymerisation reaction. Uniform electrospun fibres from this copolymer showed a water contact angle as high as 1651 with a sliding angle as low as 61. For the first time, we found that the electrospun fibres had a bundled nanofibril secondary structure with an ordered POSS morphology on the fibre surface.

Highly fluorescent TPA-PBPV nanofibers with amplified sensory response to TNT

Well-aligned nanofibers were prepared from a conjugated polymer, poly(triphenylamine-alt-biphenylene vinylene) (TPA-PBPV), using a solution-assisted template wetting technique. TPA-PBPV was also coated on the surface of electrospun polyacrylonitrile (PAN) nanofiber nonwoven membrane. The extremely large surface area, highly porous fibrous structure, optical scattering and evanescent-wave guiding effect imparted these one-dimensional (1D) nanofibrous materials with highly improved sensory ability to 2,4,6-trinitrotoluene (TNT) vapors and higher quenching efficiency than that of the neat TPA-PBPV films. The results suggest that nanofibrous structures could be a promising strategy to improve the sensory efficiency of fluorescent chemosensors.

Rotational and translational mobility of a highly plastic salt : Dimethylpyrrolidinium thiocyanate

Thermal analysis, impedance spectroscopy, NMR and Raman spectroscopy have been used to investigate the plastic crystal dimethylpyrrolidinium thiocyanate in order to gain further insight into the properties of organic ionic plastic crystals. This compound has a solid–solid phase transition at 82 °C, and melts at 122 °C. A step increase in conductivity of about one order of magnitude is observed at the phase transition, followed by a decrease in activation energy for conduction. A large entropy gain occurs at the II → I transition, and ¹H NMR linewidth measurements together with second moment calculations showed that the dimethylpyrrolidinium cation goes from a static state, to full isotropic tumbling. Raman measurements confirm that the cation as well as the anion exhibit increased rotational mobility when entering phase I.

Molecular dynamics simulations of highly concentrated salt solutions : structural and transport effects in polymer electrolytes

Structural, thermodynamic and transport properties have been calculated in concentrated non-aqueous NaI solutions using molecular dynamics simulations. Although the solvent has been represented by a simplistic Stockmayer fluid (spherical particles with point dipoles), the general trends observed are still a useful indication of the behavior of real non-aqueous electrolyte systems. Results indicate that in low dielectric media, significant ion pairing and clustering occurs. Contact ion pairs become more prominent at higher temperatures, independent of the dielectric strength of the solvent. Thermodynamic analysis shows that this temperature behavior is predominantly entropically driven. Calculation of ionic diffusivities and conductivities in the NaI/ether system confirms the clustered nature of the salt, with the conductivities significantly lower than those predicted from the Nernst-Einstein relation. In systems where the solvent-ion interactions increase relative to ion-ion interactions (lower charge or higher solvent dipole moment), less clustering is observed and the transport properties indicate independent motion of the ions, with higher calculated conductivities. The solvent in this system is the most mobile species, in comparison with the polymer electrolytes where the solvent is practically immobile.

Highly concentrated salt solutions : molecular dynamics simulations of structure and transport

Molecular dynamics (MD) simulations in NaI solutions, where the solvent has been represented by the Stockmayer fluid, were performed as a function of temperature, salt concentration, and solvent dipole strength. At higher temperatures contact ion pairs become more prevalent, regardless of solvent strength. An examination of the temperature dependence of the potential of mean force demonstrates the entropic nature of this effect. The transport properties calculated in the simulations are dependent on the balance between solvent dielectric constant and ion charge. In systems with a large solvent dipole moment, the ions appear to be independently mobile, and deviations from Nernst–Einstein behavior are small. In systems of smaller solvent dipole moment or greater ion charge, the ions form clusters, and large deviations from Nernst–Einstein behavior are observed.

N,N-Dimethylpyrrolidinium hydroxide : a highly conductive solid material at ambient temperature

N,N-Dimethylpyrrolidinium hydroxide (P₁₁OH·4H₂O) was found to exhibit high ionic conductivity in the solid state (7 × 10⁻³ S cm⁻¹ at 25°C) and unusual thermal properties, and ²H solid state NMR measurements indicate liquid-like mobility of the deuterium species in the solid state of P₁₁OD·4.5D₂O.

A new Lewis-base ionic liquid comprising a mono-charged diamine structure : a highly stable electrolyte for lithium electrochemistry

A new Lewis-base ionic liquid (IL) based on mono-charged 1,4-diazabicyclo[2.2.2]octane (dabco) was synthesized and its thermal and electrochemical behaviour was characterized. The dabco-based IL with bis(trifluoromethanesulfonyl)amide (TFSA) anion melts at 76 °C when the N-substituted alkyl chain length is 2. The dabco-based IL showed a wide electrochemical window of over 4 V ranging from −3.5 to +1.5 V vs. Fc/Fc⁺ and was able to deposit and strip lithium from a nickel substrate at reasonable efficiency.

Autocatalytic nature of permanganate oxidations exploited for highly sensitive chemiluminescence detection

Manganese(II) salts catalyze the chemiluminescent oxidation of organic compounds with acidic potassium permanganate. The formation of insoluble manganese(IV) species from the reaction between manganese(II) and permanganate can be prevented with sodium polyphosphate, and therefore, relatively high concentrations of the catalyst can be added to the reagent before the lightproducing reaction is initiated. The rapid and intense emissions from these manganese(II) catalyzed chemiluminescence reactions provide highly sensitive detection and greater compatibility with liquid chromatography.

Reactive block copolymer modified thermosets : highly ordered nanostructures and improved properties

A highly ordered poly(dimethyl siloxane)-poly(glycidyl methacrylate) (PDMS-PGMA) reactive diblock copolymer was synthesized and used to modify bisphenol A-type epoxy resin (ER). The PDMS-PGMA block copolymer consisted of epoxy-miscible PGMA blocks and an epoxy-immiscible PDMS block. The PGMA reactive block of the block copolymer formed covalent bonds with cured epoxy and was involved in the network formation, and the PDMS block phase separated to give different ordered and disordered nanostructures at different blend compositions. The solvent cast PDMS-PGMA diblock copolymer showed ordered hexagonal cylindrical morphology. A highly ordered morphology consisting of hexagonal cylinders inside the lamellar morphology was observed in the cured PDMS-PGMA block copolymer. In the cured ER/PDMS-PGMA blends, a variety of morphologies including lamellar, cubic and worm-like and spherical nanostructures were detected depending on the blend composition. Moreover, the addition of this reactive diblock copolymer significantly increases the hydrophobicity and the glass transition temperature. It also improves the tensile strength and tensile ductility of the nanostructured thermosets at low diblock copolymer contents.

Stabilization of highly unsaturated fatty acids and delivery into foods

Highly unsaturated fatty acids derived from fish or algal oils, particularly EPA and DHA, are in high demand as healthy food ingredients in fortified foods. Due to their oxidative instability most food products incorporate stabilized microencapsulated EPA and DHA oils to avoid negative sensory impact associated with oxidation of these fatty acids. Complex coacervation has been particularly successful in stabilizing fish oil and providing an ingredient with a sensory shelf-life consistent with that of the food product. Overcoming the technical challenges associated with the instability of these oils will help drive growth of the omega-3 fortified healthy food ingredient market.