Host-Guest Interactions Induce Supramolecular Assembly and Inhibit Electron Transfer to Enhance the Fluorescence Emission of Supramolecular Polymers

Three different monomers, A(2)B(2), C-2, and D-2, were synthesized. The monomers A(2)B(2) + C-2 could self-assemble to form a linear supramolecular polymer (SLP) by crown ether-based host-guest interactions at high concentrations. The electrospun nanofibers could be prepared from the SLP solution. When adding monomer D-2 to the SLP solution, the SLP transformed into a cross-linked supramolecular polymer (SCP) through the pillar[5]arene (P5)-based host-guest interaction. The SCP exhibited enhanced fluorescence emission compared to D-2 due to the inhibition of electron transfer between the P5 group and the boron-dipyrromethene (BODIPY) group on D-2. When the concentration of monomer A(2)B(2) exceeded 85 mM, the SCP turned into a SP gel and emitted green fluorescence. The gel exhibited multiple stimuli-responsiveness such as K+ and temperature responsiveness. The reversible transition of sol-gel could be achieved by K+ or temperature control, accompanied by a change of the fluorescence intensity. Additionally, the SCP gel had good self-repairing ability and thermal stability.