Probing Early-Stage Aggregation of Low Molecular Weight Gelator in an Organic Solvent.

Abstract

Molecular gels are formed by the supramolecular assembly of low molecular weight gelators (LMWGs) in organic solvents or water. Despite significant advances in the field, our understanding of how gelator molecules lead to complex self-assembled fibrillar network (SAFIN) is rather poor. Here, we present molecular dynamics simulations to gain insights into the early-stage aggregation of self-assembled fibrillar network (SAFIN) of 12-hydroxyoctadecanamide (12-HSAm) in octane. Our simulations reveal that the hydroxyl group located at the 12th carbon position plays an important role in the fiber formation. If the hydroxyl group is removed from the backbone, then we find that the aggregates adopt a bilayer morphology rather than cylindrical fibers. Analysis of fibers reveals different morphologies such as cylindrical, tape, and junction zones. A typical cylindrical fiber diameter is 2.4-3.4 nm, while the tape-like fibers are 4.4-8.6 nm in width and 2.4-4.2 nm in depth. In the fibers, we observe that the majority of the gelator molecules interact with neighboring molecules with only one interaction site, leading to growth of the fiber in one dimension. Our simulations help explain the role of functional groups in the self-assembly of small molecules leading to gel formation.