Supramolecular polymerization has become an efficient tool to organize π-conjugated molecules into long-range ordered nanostructures. Pathway complexity can be involved in the supramolecular polymerization process, leading to the formation of equilibrium thermodynamic and non-equilibrium kinetic products. Control over the kinetic complexity has paved the way of living supramolecular polymers and the synthesis of kinetically controlled supramolecular block copolymers. Cyanostilbenes represent an intriguing type of π-conjugated molecules. Although parallel and slipped packing modes have been reported for cyanostilbenes in crystals, no pathway complexity has been reported in solution state. We sought to introduce pathway complexity into cyanostilbene-based supramolecular polymers, by delicately balancing the non-covalent driving forces for the non-covalent complexation process. Specifically, N-[(1S)-phenylethyl]benzamides are embedded into the linkages of monomer, locating between the methoxy-substituted β-dicyanostilbene core and the wedge-shaped alkyl chain peripheries. The chiral linkages provide intermolecular hydrogen bonds between the neighbouring monomers, facilitating the parallel arragnement of the monomers. Meanwhile, the existence of two-fold intermolecular donor–acceptor interactions between the methoxy and cyano units give rise to the adoption of slipped arrangement of the monomers. By combination of experimental techniques with theoretical analysis, we get deeper understanding of the pathway complexity behaviors in the resulting supramolecular polymers. On this basis, we have further employed the kinetically metastable aggregates as the reactant reservoirs for the buffered release of monomer, which facilitates the seed-induced supramolecular polymerization. Our results demonstrate that the addition of seed prevents the undesired spontaneous nucleation process, and thereby promotes chain propagation for monomers from the seed termini.

Pathway complexity and seeded supramolecular polymerization of cyanostilbenes

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