Enhancement of ion dynamics in PMMA-based gels with addition of TiO2 nano-particles

Solvent and ion dynamics in PMMA based gels have been investigated as a function of the loading of nanosized TiO₂ particles. The gels have a molar ratio of 46.5:19:4.5:30 of ethylene carbonate (EC), propylene carbonate (PC), lithium perchlorate and PMMA, respectively. A series of samples with 0, 4, 6 and 8 wt.% TiO₂ filler were investigated. The diffusion coefficients for the lithium ions and for the two solvents (EC and PC) were investigated by pfg-NMR. It was shown that the addition of filler to the gel electrolytes enhances the diffusion of the cations, while the diffusion of the solvents remains constant. Raman measurements show no significant changes in ion–ion interactions with the addition of fillers, while the ionic conductivity is seen to decrease. However, the sample with 8 wt.% TiO₂ had a conductivity close to that of the unfilled sample.

Boroxine ring compounds as dissociation enhancers in gel polyelectrolytes

In order to combine the advantages of both traditional gel electrolytes and polyelectrolytes, a novel polyelectrolyte which incorporates a boroxine ring-containing anion-trapping agent has been explored. Poly(lithium 2-acrylamido-2-methyl-1-propanesulfonate) (PAMPSLi), ethylene carbonate (EC) and tri(methoxyethoxyethoxyethoxy)boroxine (TME₃Bx) were combined to prepare various gel systems. The thermal properties and conductivities of these gels have been investigated. A conductivity of 10^−3.6 S cm⁻¹ at 20 °C has been achieved in a gel polyelectrolyte system with a molar ratio of [EC]:[TME3Bx]:[Li⁺]=24:1.7:1. Temperature-dependent NMR measurements indicated that a significant interaction exists between the boroxine ring and the polyelectrolyte.

Multiple vesicular morphologies in AB/AC diblock copolymer complexes through hydrogen bonding interactions

We report for the first time multiple vesicular morphologies in block copolymer complexes formed in aqueous media via hydrogen bonding interactions. A model AB/AC diblock copolymer system consisting of polystyrene-block- poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(ethylene oxide) (PS-b-PEO) was examined using transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on PAA and PEO blocks of the two diblock copolymers. Upon the addition of PS-b-PEO, a variety of bilayer aggregates were formed in PS-b-PAA/PS-b-PEO complexes including vesicles, multilamellar vesicles (MLVs), thick-walled vesicles (TWVs), interconnected compound vesicles (ICCVs), and irregular aggregates. Among these aggregates, ICCVs were observed as a new morphology. The morphology of aggregates was correlated with respect to the molar ratio of PEO to PAA. At [EO]/[AA] = 0.5, vesicles were observed, while MLVs were obtained at [EO]/[AA] = 1. TWVs and ICCVs were formed at [EO]/[AA] = 2 and 6, respectively. When [EO]/[AA] reached 8 and above, only irregular aggregates appeared. These findings suggest that complexation between two amphiphilic diblock copolymers is a viable approach to prepare polymer vesicles in aqueous media.

Electrostatic forces induce poly(vinyl alcohol)-protected copper nanoparticles to form copper/poly(vinyl alcohol) nanocables via electrospinning

Copper/poly(vinyl alcohol) (PVA) nanocables have been successfully obtained by electrospinning a PVA-protected copper nanoparticle solution. The molar ratio of copper ions to PVA (in terms of VA repeating units) plays an important role in the formation of copper/PVA nanocables. The average diameter of the copper cores and PVA shells is about 100 and 400 nm, respectively. The structures of the copper/PVA nanocables are characterized by transmission electron microscopy (TEM) and their formation is confirmed by scanning electron microscopy (SEM).

Enzymatic synthesis of isopropyl acetate catalysed by immobilized bacillus cereus lipase in organic medium

Selective production of fragrance fatty acid ester from isopropanol and acetic acid has been achieved using silica-immobilizedlipase of Bacillus cereus MTCC 8372. A purified thermoalkalophilic extracellular lipase was immobilized by adsorption onto the silica. The effects of various parameters like molar ratio of substrates (isopropanol and acetic acid; 25 to 100 mM), concentration ofbiocatalyst (25–125 mg/mL), reaction time, reaction temperature, organic solvents,molecular sieves, and initial water activity werestudied for optimal ester synthesis. Under optimized conditions, 66.0mM of isopropyl acetate was produced when isopropanol and acetic acid were used at 100mM: 75mM in 9h at 55◦C in n-heptane under continuous shaking (160 rpm) using bound lipase(25mg). Addition of molecular sieves (3 °A ×1.5mm) resulted in a marked increase in ester synthesis (73.0mM). Ester synthesiswas enhanced by water activity associated with pre-equilibrated saturated salt solution of LiCl. The immobilized lipase retained more than 50% of its activity after the 6th cycle of reuse.

Hydrothermal synthesis of V0.13Mo0.87O2.935 nanowires with strong blue photoluminescence

Hexagonal V0.13Mo0.87O2.935 nanowires were hydrothermally synthesized at 220 °C for the first time. X-ray diffraction and field-emission scanning electron microscopy were utilized to characterize the phase and morphology of the nanowires, respectively. Transmission electron microscopy and selected area electron diffraction indicate that the nanowires are single crystalline, growing along the [001] direction. Interestingly, the nanowires easily become amorphous under the electron irradiation. The comparative hydrothermal experiments show that the molar ratio between the starting reagents of Mo and NH4VO3 plays a vital role in the anisotropic growth of nanowires. The photoluminescence measurement demonstrates that these nanowires exhibit two strong emission peaks at 420 and 438 nm, which are probably related to the intrinsic oxygen vacancies.

Optimization of milling parameters on the synthesis of stearic acid coated CaCO3 nanoparticles

Surface modification of precipitated calcium carbonate particles (calcite) in a planetary ball mill using stearic acid as a modification agent for making dispersion in hydrocarbon oil was investigated. Different parameters for processing (milling) such as milling time, ball-to-sample ratio, and molar ratio of the reactant were varied and analyzed for optimization. The physical properties of the hydrophobically modified calcium carbonate particles were measured; the particle size and morphology of the resulting samples were characterized by transmission electron microscopy and X-ray diffraction. The surface coating thickness was estimated using small angle X-ray scattering. © 2014 American Coatings Association & Oil and Colour Chemists' Association.

Self-assembled multimicellar vesicles via complexation of a rigid conjugated polymer with an amphiphilic block copolymer

A viable method of encapsulating block copolymer micelles inside vesicles using a conjugated polymer is reported in this study. Self-assembly and complexation between an amphiphilic block copolymer poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) and a rod-like conjugated polymer polyaniline (PANI) in aqueous solution were studied using transmission electron microscopy, atomic force microscopy and dynamic light scattering. The complexation and morphology transformation were driven by electrostatic interaction between PANI and the PAA block of the block copolymer. Addition of PANI to PMMA-b-PAA induced the morphology transformation from micelles to irregular vesicles through vesicles, thick-walled vesicles (TWVs) and multimicellar vesicles (MMVs). Among the observed morphologies, MMVs were observed for the first time. Morphology transformation was studied as a function of aniline/acrylic acid molar ratio ([ANI]/[AA]). Micelles were observed for the pure block copolymer, while vesicles and TWVs were observed at [ANI]/[AA] = 0.1 and 0.3, respectively. MMVs were observed at [ANI]/[AA] = 0.5 and irregular vesicles were observed for molar ratios at 0.7 and above. Clearly, a conjugated polymer like polyaniline can induce a morphology transformation even at its lower concentrations and produce complex morphologies.

Electrochemical and physicochemical properties of small phosphonium cation ionic liquid electrolytes with high lithium salt content

Electrolytes of a room temperature ionic liquid (RTIL), trimethyl(isobutyl)phosphonium (P111i4) bis(fluorosulfonyl)imide (FSI) with a wide range of lithium bis(fluorosulfonyl)imide (LiFSI) salt concentrations (up to 3.8 mol kg−1 of salt in the RTIL) were characterised using a combination of techniques including viscosity, conductivity, differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), nuclear magnetic resonance (NMR) and cyclic voltammetry (CV). We show that the FSI-based electrolyte containing a high salt concentration (e.g. 1:1 salt to IL molar ratio, equivalent to 3.2 mol kg−1 of LiFSI) displays unusual transport behavior with respect to lithium ion mobility and promising electrochemical behavior, despite an increase in viscosity. These electrolytes could compete with the more traditionally studied nitrogen-based ionic liquids (ILs) in lithium battery applications.

Characterisation of ion transport in sulfonate based ionomer systems containing lithium and quaternary ammonium cations

Two sulfonated ionomers based on poly(triethylmethyl ammonium 2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) and containing mixtures of Li⁺ and quaternary ammonium cations are characterised. The first system contains Li⁺ and the methyltriethyl ammonium cation (N1222) in a 1:9 molar ratio, and the ⁷Li NMR line widths showed that the Li⁺ ions are mobile in this system below the glass transition temperature (105°C) and are therefore decoupled from the polymer segmental motion. The conductivity in this system was measured as 10^-5 Scm^-1 at 130°C. A second PAMPS system containing Li⁺ and the dimethylbutylmethoxyethyl ammonium cation (N114(2O1)) in a 2:8 molar ratio showed much lower conductivities despite a significantly lower Tg (60°C), possibly due to associations between the Li⁺ and the ether group on the ammonium cation, or between the latter cations and the sulfonate groups.

Understanding the influence of key ionic liquid properties on the hydrolytic activity of thermomyces lanuginosus lipase

Ionic liquids (ILs) are solvents with numerous properties, which have been recently used for enzyme catalysis. In this work, five different ILs based on primary, tertiary, and quaternary ammonium cations coupled with mesylate and propionate anions were used as media for hydrolysis by the industrially relevant enzyme Thermomyces lanuginosus lipase (TLL). We correlated the TLL activity with various key IL and IL-water properties, including ion concentration, water activity (aw), kosmotropicity, hydrogen-bond basicity (β), and pH. The ion concentration was associated with aw, and the molar ratio of water/IL 5:1 (aw≈0.6) was found to be the threshold for assured TLL activity. Triethylammonium mesylate was the best IL owing to its kosmotropicity and ideal intrinsic β. The pH of IL-water mixtures is a key parameter related to the conformational change of TLL. We demonstrated the pH effect of the IL-water mixtures can be overcome by buffering, and the buffered system displayed the greatest activity.

Synergistic coassembly of two structurally different molecular gelators

Coassembly of molecules can produce materials with improved properties and functionalities. To this end, achieving a molecular level understanding of the interactions governing the coassembly is essential. In this work, two molecular gelators with significantly different structures and main intermolecular forces for assembly were coassembled. The elastic moduli of the hybrid gels are more than 1 order of magnitude higher than those of the gels formed by the individual gelators, showing an obvious synergistic effect. The interactions between the gelators were investigated with confocal microscopy and both one-dimensional and two-dimensional nuclear magnetic resonance. It was found that the two gelators coassemble to form fibers due to the nonspecific van der Waals interactions between their alkyl chains and the specific interactions between their functional groups. Switching from one gelator-dominated fiber network to the other gelator-dominated fiber network was achieved at a critical molar ratio of the gelators. The two gelators serve as additives of each other to tune the nucleation and growth of the fiber networks. The observations of this work are significant to the development of materials with improved properties by coassembly of different molecules.