Eur. Phys. J. E 5, 337-351
Scaling theory of mixed amphiphilic monolayers
Shigeyuki Komura1, 2 and S.A. Safran21 Department of Chemistry, Faculty of Science, Tokyo Metropolitan University, Tokyo 192-0397, Japan
2 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
komura@comp.metro-u.ac.jp
sam.safran@weizmann.ac.il
(Received 29 December 2000 and Received in final form 19 March 2001)
Abstract
We predict the elastic properties of mixed amphiphilic monolayers
in the swollen state within the blob model using scaling
arguments. First the elastic moduli and the spontaneous curvature
of a bimodal brush are determined as a function of the
composition and the relative chain length. We obtain simple and
useful scaling functions which interpolate between the elastic
moduli of a pure short-chain brush and a pure long-chain brush.
By using the analogy between block copolymer interfaces and
polymeric brushes, the effect of mixing on self-assembled diblock
copolymer monolayers is investigated in the swollen state. We
calculate various interfacial properties, such as the equilibrium
surface coverage, interface curvature, and the mixing free energy
as a function of the composition. In general, we find a nonlinear
dependence on the composition, which deviates from the simple
linear averaging of the properties of pure components. Our
results are used to discuss a recent experiment on the effect of
amphiphilic block copolymers on the efficiency of microemulsions.
36.20.-r - Macromolecules and polymer molecules.
68.05.-n - Liquid-liquid interfaces.
82.70.-y - Disperse systems; complex fluids.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
