posted on 2024-03-09, 14:06authored byChristopher
D. Jones, Laurence J. Kershaw Cook, Anna G. Slater, Dmitry S. Yufit, Jonathan W. Steed
Gelation by small
molecules is a topic of enormous importance in
catalysis, nanomaterials, drug delivery, and pharmaceutical crystallization.
The mechanism by which gelators self-organize into a fibrous gel network
is poorly understood. Herein, we describe the crystal structures and
gelation properties of a library of bis(urea) compounds and show,
via molecular dynamics simulations, how gelator aggregation progresses
from a continuous pattern of supramolecular motifs to a homogeneous
fiber network. Our model suggests that lamellae with asymmetric surfaces
scroll into uniform unbranched fibrils, while sheets with symmetric
surfaces undergo stacking to form crystals. The self-assembly of asymmetric
lamellae is associated with specific molecular features, such as the
presence of narrow and flexible end groups with high packing densities,
and likely represents a general mechanism for the formation of small-molecule
gels.