Understanding Pathway Complexity of Organic Micro/Nanofiber Growth in Hydrogen-Bonded Coassembly of Aromatic Amino Acids

Rational engineering of one-dimensional
(1D) self-assembled aggregates to produce desired materials for versatile
functions remains a challenge. In this work, we report the noncovalent
modulation of 1D aggregates at the micro/nanoscale using a coassembly
protocol. Aromatic amino acids were employed as the model building
blocks, and melamine (Mm) behaves as a modulator to form coassembly
arrays with aromatic amino acids selectively. The selective self-assembly
behavior between aromatic amino acids and Mm allows distinguishing
and detecting Mm and aromatic amino acids from their analogues in
macroscopic and microscopic scales. Dimensions and sizes of fibrous
aggregates prepared from different amino acids show two opposite pathways
from pristine assemblies to coassemblies induced by the addition of
Mm. This pathway complexity could be controlled by the molecular conformation
determined by α-positioned substituents. The developed hypothesis
presents an excellent expansibility to other substrates, which may
guide us to rationally design and screen 1D materials with different
dimensions and sizes including the production of high-quality self-standing
hydrogels.