| Abstract: | In the presence of a non-adsorbing polymer, monodisperse rod-like colloids assemble into one-rod-length thick liquid-like monolayer, called colloidal membranes. The physics of these micron thick fluid-like assemblages are analogous to those of two-dimensional lipid bilayers. However, their micron size allows for visualization of various membrane mediated interactions that are not possible using nanometer-sized conventional membranes. Previous work on colloidal membranes has revealed new phenomena, such as chiral control of edge tension and assembly of finite sized fluid clusters. Using the platform of colloidal membranes we describe two self-assembly pathways. In a first example we study mechanisms by which membrane imbedded 2D liquid droplets acquire unusual non-spherical shapes, suggesting that the interfacial edge domain has spontaneous non-zero edge curvature. These observations can be explained by a simple geometric argument which predicts that the edge curvature towards shorter rod domains softens the resistance of the edge to twist. In a second example, using a colloidal membrane composed of rod-like molecules of differing lengths, we study how flat two-dimensional membranes fold into 3D structures. Above critical concentration of shorter rods flat 2D membranes become unstable and assume a bewildering variety of different shapes and topologies. Simple arguments suggest that doping colloidal membranes with miscible shorter rods tunes the membrane’s Gaussian modulus, which in turn destabilizes flat 2D membranes. |
