Eur. Phys. J. E 8, 311-314 (2002)
DOI: 10.1140/epje/i2002-10021-5
SAXS investigation on aggregation phenomena in supercritical
F. Lo Celso1, A. Triolo2, F. Triolo3, D.I. Donato1, M. Steinhart4, M. Kriechbaum5, H. Amenitsch5 and R. Triolo1
1 Dipartimento di Chimica-Fisica, Università di Palermo, viale delle Scienze Parco d'Orleans II, 90128 Palermo, Italy
2 PCF-CNR, Messina, Italy
3 Mount Sinai School of Medicine, New York, USA
4 Institute of Macromolecular Chemistry, Academy of Science of the Czech Republic, Prague, Czech Republic
5 Institute of Biophysics and X-ray Structure Research, Austrian Academy of Sciences, Graz, Austria
triolo@unipa.it
(Received 25 January 2002 and Received in final form 23 April 2002)
Abstract
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 density reaches a critical value. Results of
critical micellization density (CMD) derived from pressure and
temperature ramps experiment along with the comparison with
previous SANS results are here reported to give additional experimental support
to the solvent density-driven aggregation process.
61.25.Hq - Macromolecular and polymer solutions; polymer melts; swelling.
64.75.+g - Solubility, segregation, and mixing; phase separation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002
