Please use this identifier to cite or link to this item: http://hdl.handle.net/10316/10485
Title: Mechanisms behind the Faceting of Catanionic Vesicles by Polycations: Chain Crystallization and Segregation
Authors: Antunes, Filipe E. 
Brito, Rodrigo O. 
Marques, Eduardo F. 
Lindman, Björn 
Miguel, Maria 
Issue Date: 11-Jan-2007
Publisher: American Chemical Society
Citation: The Journal of Physical Chemistry B. 111:1 (2007) 116-123
Abstract: Vesicles composed of an anionic and a cationic surfactant, with a net negative charge, associate strongly with a hydrophobically modified polycation (LM200) and with an unmodified polycation with higher charge density (JR400), forming viscoelastic gel-like structures. Calorimetric results show that in these gels, LM200 induces a rise of the chain melting temperature (Tm) of the vesicles, whereas JR400 has the opposite effect. For both polymer−vesicle systems, the shear viscosity exhibits an inflection point at Tm, and for the LM200 system the measured relaxation times are significantly higher below Tm. The neat vesicles and the polycation-bound vesicles have a polygonal-like faceted shape when the surfactant chains in the bilayer are crystallized, as probed by cryo-transmission electron microscopy. Above Tm, the neat and the LM200-bound vesicles regain a spheroidal shape, whereas those in the JR400 system remain with a deformed faceted shape even above Tm. These shape changes are interpreted in terms of different mechanisms for the polymer−vesicle interaction, which seem to be highly dependent on polymer architecture, namely charge density and hydrophobic modification. A crystallization−segregation mechanism is proposed for the LM200−vesicle system, while, for the JR400−vesicle one, charge polarization−lateral segregation effects induced by the polycation in the catanionic bilayer are envisaged.
URI: http://hdl.handle.net/10316/10485
ISSN: 1520-6106
DOI: 10.1021/jp063994+
Rights: openAccess
Appears in Collections:FCTUC Química - Artigos em Revistas Internacionais

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