Controllable supramolecular polymerization through self-sorting of aliphatic and aromatic motifs

Abstract

Self-sorting is one of the effective strategies to realize control over supramolecular polymerization. In this work, we designed a bifunctional monomer (Np-C_n-Np) bearing an alkyl chain (C_n) and two naphthalene moieties (Np). By mixing the monomer with two kinds of host molecules, the selective recognition between Np and cucurbit[8]uril (CB[8]) can link up the monomer, and the complexation between C_n and cucurbit[7]uril (CB[7]) can construct a rigid linker to promote and control the linear supramolecular polymerization. The self-sorting process was confirmed by ¹H NMR and isothermal titration calorimetry. As indicated by analytical ultracentrifugation, the molecular weight of supramolecular polymers can be well tuned from 10 kDa to 50 kDa by tuning the molar ratio of CB[7] to Np-C₆-Np. Adjustment of the length of the alkyl chain can influence the degree of polymerization, which was studied through isothermal titration calorimetry and diffusion-ordered NMR spectroscopy. In addition, the kinetics of the supramolecular polymerizations were studied by stopped flow. This line of research will extend the self-sorting strategy to achieve controllable supramolecular polymerization and enrich the field of supramolecular polymers.