Supramolecular polymerization behavior of a ditopic self-folding biscavitand

Abstract

Abstract Reported herein is the supramolecular polymerization of a mixture of a feet-to-feet connected biscavitand and a homoditopic quinuclidinium guest that is regulated by cooperativity in the host–guest association. Diffusion-ordered NMR spectroscopy (DOSY) was used to evaluate the supramolecular polymerization in toluene, CHCl3, and tetrahydrofuran (THF). Upon concentrating the solutions of the biscavitand with the quinuclidinium guest in CHCl3 and THF, the diffusion coefficient (D) values were meaningfully decreased, indicating that the host–guest complexation facilitated supramolecular polymerization. In contrast, the slight change of the D value in toluene suggests that supramolecular polymerization was suppressed, although the binding constant (K) between the cavitand and quinuclidinium guest was reported to be 105 L mol−1 in toluene. The viscosity measurements showed both the critical polymerization concentration (CPC) and entangled concentration (Ce) upon concentrating the CHCl3 solution of the mixture. Neither the CPC nor Ce was seen in the toluene solution of the mixture. Accordingly, the strong negative cooperativity in the 1:2 host–guest complexation of the biscavitand discouraged the supramolecular polymerization in toluene. These findings are valuable in deepening the understanding of host–guest association-driven supramolecular polymerization behaviors regulated by a combination of cooperativity and K value in solution.