Entropic forces stabilize diverse emergent structures in colloidal membranes

Abstract

The depletion interaction mediated by non-adsorbing polymers promotes condensation and assembly of repulsive colloidal particles into diverse higher-order structures and materials. One example, with particularly rich emergent behaviors, is the formation of two-dimensional colloidal membranes from a suspension of filamentous $fd$ viruses, which act as rods with effective repulsive interactions, and dextran, which acts as a condensing, depletion-inducing agent. Colloidal membranes exhibit chiral twist even when the constituent virus mixture lacks macroscopic chirality, change from a circular shape to a striking starfish shape upon changing the chirality of constituent rods, and partially coalesce via domain walls through which the viruses twist by $180^{\circ }$. We formulate an entropically-motivated theory that can quantitatively explain these experimental structures and measurements, both previously published and newly performed, over a wide range of experimental conditions. Our results elucidate how entropy alone, manifested through the viruses as Frank elastic energy and through the depletants as an effective surface tension, drives the formation and behavior of these diverse structures. Our generalizable principles propose the existence of analogous effects in molecular membranes and can be exploited in the design of reconfigurable colloidal structures.

17 pages, 8 figures

References in corpus (2)

• Entropically Driven Helix Formation
• Hierarchical organization of chiral rafts in colloidal membranes

Cited by in corpus (14)

• Molecular engineering of chiral colloidal liquid crystals using DNA origami
• Entropy-driven formation of prolate and oblate cholesteric phases by computer simulations
• Achiral symmetry breaking and positive Gaussian modulus lead to scalloped colloidal membranes
• Chiral twist drives raft formation and organization in membranes composed of rod-like particles
• Chiral edge fluctuations of colloidal membranes
• Filamentous phages as building blocks for reconfigurable and hierarchical self-assembly
• Conformational switching of chiral colloidal rafts regulates raft-raft attractions and repulsions
• Theory of microphase separation in bidisperse chiral membranes
• Interaction of chiral rafts in self-assembled colloidal membranes
• The Thermodynamic Origins of Chiral Twist in Monolayer Assemblies of Hard Rod-like Colloids
• Deformation and orientational order of chiral membranes with free edges
• Probing a self-assembled fd virus membrane with a microtubule
• Shapes of fluid membranes with chiral edges
• Elastic moduli of a smectic membrane: a rod-level scaling analysis