Search results for "Aqueous-solutions"
showing 9 items of 9 documents
Water and temperature contribution to the structuration of starch matrices in the presence of flavour.
2016
The effect of hydrothermal treatments and flavours addition on starch structure and its physical properties were studied. Native wheat starch was treated at 2 different hydrations (water-starch ratios: 50/50 and 80/20 g w/w) and temperatures (65 and 85 °C) in the presence of flavours (ethyl hexanoate and 2-hexanone). The freshly prepared samples were subjected to DSC and flavour analysis. Flavour inclusion complex could not be detected by DSC, however the result of flavour analysis proved that there were flavours interactions with starch. Both ethyl hexanoate and 2-hexanone interacted with starch at similar rates. The highest flavour loss was found in the samples at high hydration and heate…
Structural Organization of Poly(vinyl alcohol) Hydrogels Obtained by Freezing and Thawing Techniques: A SANS Study
2005
The structural organization of matter in poly(vinyl alcohol) (PVA) hydrogels obtained by repeatedly freezing and thawing dilute solutions of PVA in D2O is investigated by use of small-angle neutron scattering measurements (SANS). This study is the first systematic and quantitative investigation in the medium range of length scales on PVA hydrogels obtained by freezing and thawing techniques. The studied gels have a complex hierarchical structure, extending over a wide range of length scales. The structural organization on the micron length scale originates from the presence of two separated phases constituted by polymer-rich and polymer-poor regions. The network structure may be interpreted…
Ultrasound-assisted MnO2 catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics
2013
Abstract The combination of peracetic acid (PAA) and heterogeneous catalyst (MnO 2 ) was used for the degradation of phenol in an aqueous solution in the presence of ultrasound irradiation (US). As a relevant source of free radicals (e.g. OH), peracetic acid was comprehensively studied by means of electron spin resonance (ESR) spin trapping (ST) techniques with the subsequent identification of free radicals by simulation based fitting (SBF) technique. The radical reaction mechanism, where hydroxyl radical was a primary product of O O bond rupture of PAA, was established taking into account radical reactions, occurring during sonolysis. The potential barriers and the reaction heat were deter…
Polystyrene nanoparticles in the presence of (ethylene oxide)13(propylene oxide)30(ethylene oxide)13, N,N-dimethyloctylamine-N-oxide and their mixtur…
2008
Polystyrene nanoparticles were synthesized by emulsion polymerization of styrene. They were functionalized using the conventional surfactant N,N-dimethyloctylamine-N-oxide (ODAO), the tri-block copolymer (ethylene oxide)13(propylene oxide)30(ethylene oxide)13 (L64) and their mixtures. To this purpose, dynamic light scattering and calorimetric experiments were carried out and provided information consistent to each other. The L64 adsorption is Langmuir-type in the copolymer dilute regime and generates complex structures at larger concentrations. In the region where ODAO is in the unimeric state, the adsorption process is cooperative leading to hemi-micelle formation at the polystyrene nanopa…
Adsorption of triblock copolymers and their homopolymers at laponite clay/solution interface. Role played by the copolymer nature
2009
The adsorption thermodynamics of copolymers, based on ethylene oxide (EO) and propylene oxide ( PO) units, at the laponite (RD) clay/liquid interface was determined at 298 K. The copolymer nature was tuned at molecular level by changing the hydrophilicity, the architecture and the molecular weight (Mw) keeping constant the EO/PO ratio. Polyethylene (PEGs) and polypropylene (PPGs) glycols with varying Mw and their mixture were also investigated to discriminate the role of the EO and the PO segments in the adsorption process. Enthalpies of transfer of RD, at fixed concentration, from water to the aqueous macromolecule solutions as functions of the macromolecule molality were determined. They …
Micelles in Mixtures of Sodium Dodecyl Sulfate and a Bolaform Surfactant
2006
Mixtures composed of water, sodium dodecyl sulfate (SDS), and a bolaform surfactant with two aza-crown ethers as polar headgroups (termed Bola C-16) were investigated by modulating the mole ratios between the components. The two surfactants have ionic and nonionic, but ionizable, headgroups, respectively. The ionization is due to the complexation of alkali ions by the aza-crown ether unit(s). Structural, thermodynamic, and transport properties of the above mixtures were investigated. Results from surface tension, translational self-diffusion, and small angle neutron scattering ( SANS) are reported and discussed. Interactions between the two surfactants to form mixed micelles result in a com…
Structural behaviour differences in low methoxy pectin solutions in the presence of divalent cations (Ca 2+ and Zn 2+ ): a process driven by the bind…
2014
International audience; In this paper, we compare the interactions between low methoxy pectin (LMP) and either Ca2+ or Zn2+ in semi-dilute solutions. Intrinsic viscosity and turbidity measurements reveal that pectin-calcium solutions are more viscous, but yet less turbid, than pectin-zinc ones. To get a molecular understanding on the origin of this rather unexpected behavior, we further performed isothermal titration calorimetry, small angle neutron scattering experiments, as well as molecular dynamics simulations. Our results suggest that calcium cations induce the formation of a more homogeneous network of pectin than zinc cations do. The molecular dynamics simulations indicate that this …
A Combined Experimental and Theoretical Approach to the Photogeneration of 5,6-Dihydropyrimidin-5-yl Radicals in Nonaqueous Media
2016
The chemical fate of radical intermediates is relevant to understand the biological effects of radiation and to explain formation of DNA lesions. A direct approach to selectively generate the putative reactive intermediates is based on the irradiation of photolabile precursors. But, to date, radical formation and reactivity have only been studied in aqueous media, which do not completely mimic the micro environment provided by the DNA structure and its complexes with proteins. Thus, it is also important to evaluate the photogeneration of nucleoside-based radicals in nonaqueous media. The attention here is focused on the independent generation of 5,6-dihydropyrimidin-5-yl radicals in organic…
Thermal potential of ion-exchange membranes and its application to thermoelectric power generation
2016
The low efficiency and high price of thermoelectric semiconductors has generated interest in unconventional forms of thermoelectric materials. In this article, ionic thermoelectricity has been studied with commercial ion-exchange membranes for different aqueous 1:1 electrolytes. The theory of thermal membrane potential has been derived taking into account the ionic heats of transport, the non-isothermal Donnan potentials, the temperature polarization, and the thermally-induced concentration polarization of the electrolyte. Also the generated thermoelectric power has been experimentally studied. The experiments show good agreement with the theory, and suggest ways for systematic improvement …