Enhancing Insulated Conjugated Polymer Fluorescence Quenching by Incorporating Dithia[3.3]paracyclophanes

Insulated pi-conjugated polymers exhibit enhanced chemical stability, photostability, fluorescence quantum yield, electroluminescence, solubility, and intrachain charge transport. However, insulated polymer fluorescence quenching by acceptor molecules is significantly hampered as the pi-face is insulated. Photoinduced charge transfer is one of the key steps in amplified fluorescence quenching sensors and organic solar cells for charge generation. Inspired by the myelin sheath gaps in nerve cell axons, herein, we synthesized a series of insulated random copolymers of adamantanocyclophane with an increasing percentage of dithia[3.3]paracyclophane (PCP) from 5 to 30% to enhance the insulated polymer fluorescence quenching with acceptor molecules. As the percentage of the dithia[3.3]paracyclophane monomer increases, the copolymers showed an increase in absorption in the red region of the spectrum and also the copolymers' photoluminescence quantum yield reduced. The Stern-Volmer quenching constant of the 30% copolymer is ca. 4.5 times higher than that of the adamantanocyclophane homopolymer. A comparison with the control polymers indicated that the through-space-coupled interactions in PCP could be a plausible reason for the enhanced fluorescence quenching in copolymers in addition to the reduced steric hindrance by PCP. The developed copolymers combine the advantages of polymer insulation without significantly sacrificing the photoinduced charge transfer, which will help further their applicability as amplified fluorescence quenching sensors and in organic solar cells.