Entropically controlled assemblies of conjugated amphiphiles

Abstract

Amphiphiles with conjugated subunits possess favorable optical and electronic properties as well as the intrinsic ability to propagate these features across scales via supramolecular self-assembly. These capabilities highlight their tremendous potential for applications in drug delivery, sensing, flexible electronics, and/or integrated circuits. However, achieving systematic control over their self-assembled morphologies remains challenging due to the lack of understanding on how the effects of molecular geometry propagate across hierarchical length scales to influence their mesoscale assembly behaviors. Herein, we employ a combination of molecular dynamics simulations and a scaling theory to characterize the assembly behaviors for a model system of conjugated amphiphiles. Firstly, we demonstrate how variations in the length of each amphiphilic block modulate its equilibrium supramolecular self-assembly behaviors using a coarse-grained simulation model that preserves the intrinsic molecular-level geometries of each respective conjugated motif. Then, we employ a scaling theory to elucidate the microscopic interactions driving the observed morphological shifts in simulations. Our findings reveal that the supramolecular self-assembly of conjugated amphiphiles is governed by a balance between association enthalpy arising from π–π interactions and entropic penalties arising from geometry-mediated steric repulsions. Then, we leveraged the insights provided by simulation and theory to predict a suite of self-assembled morphologies accessible using our model amphiphilic system across experimentally testable design parameters. Our findings not only establish a practical approach to simulate the mesoscale self-assembly of conjugated amphiphiles but also provide important insights into the microscopic mechanisms underlying their macroscopic behaviors.