Control over the Geometric Shapes and Mechanical Properties of Uniform Platelets via Tunable Two-Dimensional Living Self-Assembly

It remains unexplored how the living self-assembly of
small molecules
can gain control over the geometric shapes and mechanical properties
of the two-dimensional (2D) platelets fabricated therefrom. Herein,
we report a tunable 2D living self-assembly method to control the
geometric shape variety and mechanical properties of the resulting
uniform 2D platelets. This new approach of using n-alkyl alcohols to connect a donor–acceptor (D–A) molecule
into a 2D network via hydrogen bonding has a threefold effect on the
formed 2D platelets. First, the intralayer molecular packing involving
continuous hydrogen bonds between a D–A fluorophore and alcohols
remains unaltered, thereby yielding the same optical properties and
thermal stability to various 2D platelets. Second, the kinetic growth
differentiation of the D–A fluorophore and alcohol in two dimensions
depends on the interaction competition of alcohol with the D–A
fluorophore against hexane (a poor solvent), engendering the alcohol-dependent
2D shape variety. Third, the interlayer interactions along the thickness
of the platelet can be effectively modulated by the alcohol tails
with different lengths that stretch out of each bilayer, thereby varying
the mechanical properties of the 2D platelets, for which Young’s
moduli and hardnesses decrease significantly with the increasing tail
length of the alcohols.