Circularly Polarized Luminescence (CPL)‐Active Homo‐ and Heterostructures by Surface‐Catalyzed Secondary Supramolecular Polymerization

ABSTRACT Surface‐catalyzed secondary nucleation is well‐known in protein aggregation but underexplored in supramolecular polymerization of π‐systems. Herein, we report a unique example of multistep secondary nucleation‐dominated controlled supramolecular polymerization of an amide‐functionalized naphthalene monoimide derivative ( O‐NMI‐1 ) in a methylcyclohexane:decane mixture, undergoing a stepwise transformation from a metastable particle to crystalline nanorods via intermediate nanotapes over 48 h. The resulting hydrogen‐bonded nanorods display enhanced emission, a high quantum yield (34%) and strong circularly polarized luminescence (CPL), revealing an unprecedented correlation between their structural evolution and the time‐dependent increment in the CPL intensity, reaching an appreciably high luminescence dissymmetry factor ( g _lum ) of ∼0.088 in the film state. Contrastingly, the seeded polymerization of O‐NMI‐1 follows a fragmentation‐dominated mechanism, yielding unexpected fragmented nanorods in multi‐seeding cycles. Control experiments with a structurally similar analogue ( O‐NMI‐2 ), lacking a methylene spacer, revealed no CPL, highlighting the spacer's crucial role in controlling the excited‐state chiral emission. The contrasting behavior between the two monomers enabled hetero‐seeded polymerization of O‐NMI‐1 nanorods from O‐NMI‐2 fibrillar seeds, producing CPL‐active unique heterostructures under kinetic control from two initial CPL‐silent components. The present findings unveil the overlooked impact of secondary nucleation in temporal control of supramolecular chirality and CPL‐activity in homo‐ and heterostructures of supramolecular polymers.