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RESEARCH PRODUCT

Pressure-Induced Formation of Diblock Copolymer "Micelles" in Supercritical Fluids. A Combined Study by Small Angle Scattering Experiments and Mean-Field Theory. I: the Critical Micellization Density Concept

Roberto TrioloF. Lo CelsoAlessandro TrioloAntonio Raudino

subject

chemistry.chemical_classificationQuantitative Biology::BiomoleculesMaterials scienceSmall-angle X-ray scatteringGeneral Physics and AstronomyThermodynamicsPolymerSupercritical fluid extraction Carbon dioxide dispersion polymerizationSupercritical fluidCondensed Matter::Soft Condensed MatterMean field theorychemistryPhase (matter)CopolymerOrganic chemistryPolymer blendPhysical and Theoretical ChemistrySolvent effects

description

We developed a simple mean-field theory to describe polymer and AB diblock copolymer phase separation in supercritical (SC) fluids. The highly compressible SC fluid has been described by using a phenomenological hole theory, properly extended to consider the solvent/polymer/vacancy pseudoternary mixture. The model has been applied to describe the phase behavior of AB-diblock copolymers under the assumption of a strong solvent selectivity for just one copolymer chain. In our model the solvent selectivity is a strong function of the external pressure because in compressible fluids vacancies reduce the number of favorable solvent-polymer contacts. The combined effect of the pressure on the average solvent quality and selectivity for a single polymer chain makes the phase behavior of a diblock copolymer in SC fluids quite complex. Small angle neutron and x-ray scattering (SANS and SAXS) measurements have been performed on SC-CO2 solutions of different AB-diblock copolymers containing a perfluorinated chain. The data obtained over a wide range of pressure and temperature confirm our theoretical predictions.

yearjournalcountryeditionlanguage
2004-01-01
10.1063/1.1640998http://hdl.handle.net/10447/14348