Solvent Microheterogeneity-Regulated Supramolecular Morphological Anisotropy in an Aggregation-Induced Emission-Active Phenylalanine Derivative

Abstract Solvent–solute interactions play a crucial role in directing the morphological evolution of supramolecular polymers. Different noncovalent interactions, such as hydrogen bonding, hydrophobic effects, and chirality, are modulated by solvents to yield anisotropic architectures. However, the influence of composition-dependent microheterogeneity in mixed solvents on cooperative self-assembly processes and the resulting structural anisotropy remains poorly understood. Herein, we report the supramolecular self-assembly of an aggregation-induced emission-active phenylalanine derivative, l-PhePy, in MeOH–H2O mixtures of varying compositions. Notably, the solvent microheterogeneity has a pronounced influence on morphological outcomes, yielding amorphous microrods at 60% water content, crystalline fractal networks at 90%, and vesicular amorphous spheres at 95%. Mechanistic studies reveal that solvent microheterogeneity modulates noncovalent interactions, shaping both the kinetic and thermodynamic parameters of the assembled process and inducing phase segregation that confines structures at interfaces. Interestingly, under specific solvent conditions, fractal architectures emerge through a diffusion-limited aggregation pathway enabled by cooperative chiral growth, whereas rod-like and vesicular structures evolve via an isodesmic assembly pathway. These findings reveal the critical, yet often overlooked, role of microheterogeneity in mixed solvents in directing supramolecular polymerization, providing a framework for designing anisotropic supramolecular materials with emergent and optimized properties.