Small-Angle X-ray Scattering Insights into the Architecture-Dependent Emulsifying Properties of Amphiphilic Copolymers in Supercritical Carbon Dioxide

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• 作者：David Alaimo ; Daniel Hermida Merino ; Bruno Grignard ; Wim Bras ; Christine J茅r么me ; Antoine Debuigne ; Cedric J. Gommes
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：January 29, 2015
• 年：2015
• 卷：119
• 期：4
• 页码：1706-1716
• 全文大小：513K
• ISSN：1520-5207

文摘

The supramolecular assembly of a series of copolymers combining poly(ethylene oxide)-rich hydrophilic and fluorinated CO₂-philic sequences is analyzed by synchrotron small-angle X-ray scattering (SAXS) in supercritical CO₂, as well as in water/CO₂ emulsions. These copolymers were designed to have the same molecular weight and composition and to differ only by their macromolecular architecture. The investigated copolymers have random, block, and palm-tree architectures. Besides, thermoresponsive copolymer is also analyzed, having a hydrophilic sequence becoming water-insoluble around 41 掳C, i.e., just above the critical point of CO₂. At the length scale investigated by SAXS, only the random copolymer appears to self-assemble in pure CO₂, in the form of a disordered microgel-like network. The random, block, and thermoresponsive copolymers are all able to stabilize water/CO₂ emulsions but not the copolymer with the palm-tree architecture, pointing at the importance of macromolecular architecture for the emulsifying properties. A modeling of the SAXS data shows that the block and the thermoresponsive copolymers form spherical micelle-like structures containing about 70% water and 30% polymer.