Programming the organization of π‐conjugated systems into nanostructures of defined dimensions is a requirement for the preparation of functional materials. Herein, we have achieved high‐precision control over the self‐assembly pathways and fiber length of an amphiphilic BODIPY dye in aqueous media by exploiting a programmable hydrogen bonding lock. The presence of a (2‐hydroxyethyl)amide group in the target BODIPY enables different types of intra‐ vs. intermolecular hydrogen bonding, leading to a competition between kinetically controlled discoidal H‐type aggregates and thermodynamically controlled 1D J‐type fibers in water. The high stability of the kinetic state, which is dominated by the hydrophobic effect, is reflected in the slow transformation to the thermodynamic product (several weeks at room temperature). However, this lag time can be suppressed by the addition of seeds from the thermodynamic species, enabling us to obtain supramolecular polymers of tuneable length in water for multiple cycles.

Externally-initiated controlled supramolecular polymerization of the kinetically trapped aggregated state in a chain growth mechanism can produce well-defined living supramolecular polymers and copolymers.

Peptide-based hydrogels are highly promising for various biomedical applications owing to their precise selfassembly, biocompatibility, and sensitivity toward biologically relevant external stimuli. Herein, we report pH-responsive selfassembly and gelation of a highly biocompatible amphiphilic peptide PEP-1. This is an octa-peptide and double mutant of a naturally occurring β-strand peptide fragment of the protein Galectin-1, available in bovine spleen. PEP-1 was synthesized by using the Rink amide resin as the solid support in a homemade apparatus. At pH 7.4, it exhibits spontaneous gelation with very high yield stress of 88.0 Pa and gel-to-sol temperature of 84 °C at C = 2.0 wt %. Microscopy studies revealed entangled fibrillar morphology whereas circular dichroism, Fourier tranform IR, and Thioflavin T assay indicated formation of β-sheet rich secondary structure. The assembled state was found to be stable in neutral pH whereas either decrease or increase in the pH resulted in disassembly owing to the presence of the pH responsive Asp and Lys residues. The gel network showed ability to entrap water-soluble guest molecules such as Calcein which could be selectively released at acidic pH whereas under neutral condition the release was negligible. MTT assay revealed remarkable biocompatibility of the PEP-1 gel as almost 100% cells were alive after 48 h incubation in the presence of PEP-1 (2.0 mg/mL).

cNDI-1 exhibits an off-pathway aggregate in cyclic hydrocarbon (MCH) but produces a helical supramolecular polymer in linear alkane (decane) by well-defined J-aggregation. Effective solvent-assisted nucleation in linear alkanes due to shape matching with the peripheral alkyl chains of a monomer is responsible for the pathway complexity. Seed, produced by sonication induced fragmentation of the fibers in decane, could initiate supramolecular polymerization of the off-pathway aggregate in MCH generating controllable helical nanostructures. The chiral seed of cNDI-1 was also successfully employed for the synthesis of a helical supramolecular polymer from the off-pathway aggregate of achiral cNDI-2.

Herein, the impact of alkyl bridge length is unraveled on the self‐assembly of N‐annulated perylenetetracarboxamides 1–4 that cooperatively form supramolecular polymers. Spectroscopic studies in different solvents as media for the self‐assembly demonstrate the impact that the length of the bridge separating the two amide groups of compounds 1–4 exerts on the supramolecular polymerization process: i) in MCH/Tol (8/2), compounds 1–3 exhibit a consecutive process that, however, it is not operative for 4; ii) the presence of three methylene units in 2, which can induce a parallel distribution of the amide groups, notably decreases the stability of the corresponding aggregates in Tol; iii) increasing the spacer length accelerates the conversion of the metastable, intramolecularly H‐bonded monomeric species, which prevents to develop seeded supramolecular polymerizations; iv) the presence of a spacer with five methylene units in 4 hinders the formation of the corresponding 10‐membered pseudo‐cycle; and v) only the higher relative stability of the inactivated monomeric species of 1 enables pathway complexity, with a kinetically controlled self‐assembly to yield nanoparticles and a thermodynamically controlled supramolecular polymerization to achieve fibrillar structures. The results presented herein expand the knowledge on the structure/property relationship for self‐assembling units to provide pathway complexity and to bias the kinetics and stability of the supramolecular aggregates.