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.
Through a good/poor solvent strategy, native folic acid (FA) which behaves as a super-gelator in DMSO-water system can be successfully employed to construct supramolecular gels. The system exhibited morphological evolution with the increase of FA concentration; various phases such as vesicles, fiber/vesicles, fiber/nanoparticles, nanoparticles were probed. In the self-assembly process, l-glutamic acid moiety induced the formation of helical 1-dimensional (1-D) fibers which further self-assembled into a gel. Stimuli like heat, stress, pH and light which affect the molecular structure of FA or solubility in the mixed solvents had a pronounced influence on the properties of the gels, such as mechanical properties or bulk phases. A time-dependent oscillatory stress scan indicated that the supramolecular gel had a self-healing property. Without tedious modification routes and addition of alkali metal ions, native FA which served as an efficient building block and super-gelator to build up multi-responsive and self-recovery material was investigated for the first time.
In the solid state, amino acids (alanine and phenylglycine) with appended pyrene segments self‐assembled into α‐helix‐like structures by asymmetrical H‐bonds between carboxylic acid and amide segments, further inducing supramolecular tilted chirality of the achiral pyrenes. These structures bind melamine and electron‐deficient units through H‐bond and charge‐transfer interactions, respectively. Charge‐transfer interactions enhance the dissymmetry g‐factor of absorption (gabs; up to 1.4×10−2) with an extended Cotton effect active region (from 250 to 600 nm). Incorporating melamine inverts the handedness of circularly polarized luminescence and boosts the dissymmetry g‐factor (glum). Melamine also induces macroscopic chirality at the nanoscale, whereby the 2D lamellar structures are transformed into 1D helices at the nanoscale, leading to giant tubular structures at the microscale.
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