Derivation of expressions for the spontaneous curvature, mean and Gaussian bending constants of thermodynamically open surfactant monolayers and bilayers
2003 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, no 3, 1440-1452 p.Article in journal (Refereed) Published
We have derived expressions for the spontaneous curvature H-0, the mean and Gaussian bending constants, k(c) and (k) over bar (c), respectively, for a surfactant film of finite thickness that is open in a thermodynamic sense. Geometrical packing constraints are taken into account and give rise to explicit large and important contributions to k(c), (k) over bar (c), and k(c)H(0). From its contribution to the latter quantity we may deduce that surfactant aggregates (micelles, vesicles, microemulsion droplets) are expected to dramatically increase their size with increasing surfactant tail length. Moreover, the coupling between free energy contributions related to surfactant head group and tail with geometrical packing constraints give rise to dominant terms on the form 2xi(p)H(0), where xi(p) is the thickness of a planar film, in the expressions for k(c). In the case of repulsive head group effects that favor a large spontaneous curvature, such as electrostatics, these terms raise k(c) and thus increase the rigidity of the film. Due to the constraint of constant free monomer chemical potentials, the composition of the film becomes a function of curvature. As a result, the ability of a surfactant film to have different surfactant compositions in differently curved parts (e.g., inner and outer layer of a vesicle, central parts and end caps of rod or threadlike micelles, etc.) may considerably reduce k(c), whereas (k) over bar
Place, publisher, year, edition, pages
2003. Vol. 118, no 3, 1440-1452 p.
angle neutron-scattering, sodium dodecyl-sulfate, charged membranes, free-energy, molecular interpretation, cationic surfactants, nonionic surfactants, aqueous-solutions, vesicle bilayer, phase-behavior
IdentifiersURN: urn:nbn:se:kth:diva-22162DOI: 10.1063/1.1528910ISI: 000180316700051OAI: oai:DiVA.org:kth-22162DiVA: diva2:340860
QC 201005252010-08-102010-08-10Bibliographically approved