0000000000303953
AUTHOR
Heinz Amenitsch
SAXS investigation on aggregation phenomena in supercritical CO2.
Synchrotron Small-Angle X-Ray scattering (SAXS) measurements on aggregate formation of a Polyvinyl acetate- b-Perfluoro octyl acrylate (PVAc- b-PFOA) block copolymer in supercritical CO(2) are here reported. Experiments were carried out for a series of different thermodynamic conditions, changing the solvent density by profiling both the pressure at constant temperature and the temperature at constant pressure. This block copolymer and in general fluorocarbon-hydrocarbon di-blocks form aggregates depending on the value of CO(2) density. A sharp transition between monomers dissolved as random coils and micelles characterized by a solvophilic shell and a solvophobic core occurs when the CO(2)…
Industrial applications of the aggregation of block copolymers in supercritical CO 2 : a SANS study
Industrial applications of supercritical carbon dioxide (scCO2) rely upon the rather selective and easily adjustable solvent ability of CO2. CO2 near the critical point is a poor solvent for high molecular weight (HMW) hydrocarbon polymers, while it is a very good solvent for amorphous fluorinated polymers. By increasing the pressure, CO2 becomes a good solvent even for HMW hydrogenated chains. Specially engineered amphiphilic di-block copolymers, with CO2-philic and CO2-phobic portions, are expected to undergo trough a monomer–aggregate transition when the solvent density of the scCO2 changes. Here small-angle neutron scattering (SANS) results are reported for a block copolymer dissolved i…
Kinetics of block-copolymer aggregation in super critical CO2
Small angle X-ray and neutron scattering (SAXS and SANS) are used to obtain structural information on the aggregation behavior of block-copolymers dissolved in supercritical CO2. The SANS technique is used to provide a detailed structural model for the micellar aggregates, which form below the critical micellization density (CMD), that we defined in our previous work. The SAXS technique (with a synchrotron source) is used to provide the first experimental information concerning the kinetic features of both formation and decomposition of such aggregates as soon as pressure jumps are applied to the solutions across the CMD. 2002 Elsevier Science B.V. All rights reserved.
Pressure effects on α-synuclein amyloid fibrils: An experimental investigation on their dissociation and reversible nature
αâsynuclein amyloid fibrils are found in surviving neurons of Parkinson's disease affected patients, but the role they play in the disease development is still under debate. A growing number of evidences points to soluble oligomers as the major cytotoxic species, while insoluble fibrillar aggregates could even play a protection role. In this work, we investigate αâsynuclein fibrils dissociation induced at high pressure by means of Small Angle X-ray Scattering and Fourier Transform Infrared Spectroscopy. Fibrils were produced from wild type αâsynuclein and two familial mutants, A30P and A53T. Our results enlighten the different reversible nature of αâsynuclein fibrils fragmentati…
Investigation on a MMACHC mutant from cblC disease: The c.394C>T variant
The cblC disease is an inborn disorder of the vitamin B12 (cobalamin, Cbl) metabolism characterized by methylmalonic aciduria and homocystinuria. The clinical consequences of this disease are devastating and, even when early treated with current therapies, the affected children manifest symptoms involving vision, growth, and learning. The illness is caused by mutations in the gene codifying for MMACHC, a 282aa protein that transports and transforms the different Cbl forms. Here we present data on the structural properties of the truncated protein p.R132X resulting from the c.394C > T mutation that, along with c.271dupA and c.331C > T, is among the most common mutations in cblC. Althou…
Preparation of multi-nanocrystalline transition metal oxide (TiO2–NiTiO3) mesoporous thin films
Ordered mesoporous TiO2–NiTiO3 thin films, with nickel content x < 0.5, were prepared by dip-coating an acidic solution of hydrolysed transition metal chlorides in controlled humidity, followed by a very careful annealing treatment. These latter treatments were studied by in situ SAXS-WAXS experiments involving synchrotron radiation and TEM analysis. They revealed that the walls can be composed of amorphous, single crystalline or multi crystalline nanoparticles depending on x and the conditions applied during the thermal treatment.
Morphology of solid polymer electrolytes: a TR WAXS investigation
A wide angle X-ray scattering investigation of (polyethylene oxide)n–sodium thiocyanate [(PEO)nNaSCN] mixtures is reported. Temperature dependence analysis for different mixtures is shown, in order to rationalize the multi-phase behaviour. Depending on the amount of salt added and upon the temperature considered three different phases have been found to simultaneously coexist: crystalline PEO, amorphous PEO, and crystalline complex.
A combined small-angle neutron and X-ray scattering study of block copolymers micellisation in supercritical carbon dioxide
Small angle neutron and X-ray scattering (SANS and SAXS) are used to investigate the monomer–aggregate transition of fluorocarbon–hydrocarbon diblock copolymers in supercritical carbon dioxide. SANS data are analyzed using a polydisperse sphere core–shell model. Synchrotron SAXS data have been collected by profiling the pressure at different temperatures, and critical micellization densities have been obtained for a series of diblock solutions. Finally pressure jump experiments, combined with synchrotron SAXS, have revealed two steps in the dynamics of the formation of the aggregates.