Compatibility between Solid Particles and a Lamellar Phase: A Crucial Role of the Membrane Interactions

From previous studies, we know that Helfrich-stabilized smectic phases can incorporate solid particles of typical size 10 nm between their membranes; the incorporation of magnetic particles yields a “ferrosmectic” phase. We present here a study of the compatibility between such solid particles and a lamellar phase versus the interactions between membranes. The type of stabilizing forces, from purely electrostatic to purely entropic, is varied via the concentration of salt (NaCl) in a swollen lamellar phase. The experimental results reported in this paper show that the Helfrich phases can incorporate particles within their lamellar matrix, whereas particles are excluded from the electrostatic phases. A semiquantitative interpretation based on considerations about the interactions between particles and membranes is given.