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The Morphology of Block Copolymer Micelles in Supercritical Carbon Dioxide by Small‐Angle Neutron and X‐ray Scattering
Author(s) -
Londono J. D.,
Dharmapurikar R.,
Cochran H. D.,
Wignall G. D.,
McClain J. B.,
Betts D. E.,
Canelas D. A.,
DeSimone J. M.,
Samulski E. T.,
ChilluraMartino D.,
Triolo R.
Publication year - 1997
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889897002446
Subject(s) - copolymer , fluoropolymer , supercritical carbon dioxide , micelle , supercritical fluid , polymer , neutron scattering , chemical engineering , small angle neutron scattering , polymer chemistry , materials science , polystyrene , chemistry , scattering , organic chemistry , aqueous solution , optics , physics , engineering
Above its critical point, carbon dioxide forms a super‐critical fluid, which promises to be an environmentally responsible replacement for the organic solvents traditionally used in polymerizations. Many lipophilic polymers such as polystyrene (PS) are insoluble in CO 2 , though polymerizations may be accomplished via the use of PS‐fluoropolymer stabilizers, which act as emulsifying agents. Small‐angle neutron and X‐ray scattering have been used to show that these molecules form micelles with a CO 2 ‐phobic PS core and a CO 2 ‐philic fluoropolymer corona. When the PS block was fixed in length and the fluorinated corona block was varied, the number of block copolymer molecules per micelle (six to seven) remained constant. Thus, the coronal block molecular weight exerts negligible influence on the aggregation number, in accordance with the theoretical predictions of Halperin, Tirrell & Lodge [ Adv. Polym. Sci. (1992), 100 , 31–46]. These observations are relevant to understanding the mechanisms of micellization and solubilization in supercritical fluids.