Mechanism
of Self-Assembly Process and Seeded Supramolecular
Polymerization of Perylene Bisimide Organogelator
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Abstract
The mechanism of supramolecular polymerization
has been elucidated
for an archetype organogelator molecule composed of a perylene bisimide
aromatic scaffold and two amide substituents. This molecule self-assembles
into elongated one-dimensional nanofibers through a cooperative nucleation–growth
process. Thermodynamic and kinetic analyses have been applied to discover
conditions (temperature, solvent, concentration) where the spontaneous
nucleation can be retarded by trapping of the monomers in an inactive
conformation, leading to lag times up to more than 1 h. The unique
kinetics in the nucleation process was confirmed as a thermal hysteresis
in a cycle of assembly and disassembly processes. Under appropriate
conditions within the hysteresis loop, addition of preassembled nanofiber
seeds leads to seeded polymerization from the termini of the seeds
in a living supramolecular polymerization process. These results demonstrate
that seeded polymerizations are not limited to special situations
where off-pathway aggregates sequester the monomeric reactant species
but may be applicable to a large number of known and to be developed
molecules from the large family of molecules that self-assemble into
one-dimensional nanofibrous structures. Generalizing from the mechanistic
insight into our seeded polymerization, we assert that a cooperative
nucleation–growth supramolecular polymerization accompanied
by thermal hysteresis can be controlled in a living manner