Supramolecular polymers are regarded as a new kind of dynamic materials. The study of supramolecular polymers not only helps to understand the law of self-assembly, but also provides theoretical support for the development of smart materials. Herein, three dioxyphenylene bridged ditopic ureidopyrimidinone (UPy) derivatives M1~M3 are studied. These molecules could undergo supramolecular polymerization via quadruple hydrogen bonding. The only difference in their structure is the length of the oligo(ethylene oxide) chain as spacers. The supramolecular polymerization based on ring-chain equilibrium of these molecules were studied by a series of experiments including concentration-dependent ¹H NMR, NOESY, and viscosity measurement, which showed that the spacer length has a big impact on the ring-opening supramolecular polymerization process. And the main reason for this is the different strengths of π-π interaction between the dioxyphenylene unit and the dimerized UPy motif in the cyclic monomer form. M1 with the shortest spacer lacks this kind of π-π interaction while M3 with the longest spacer possesses a weak π-π interaction, both leading to small value of CPCs. By contrast, M2 with a moderate length of spacer has a strong π-π interaction, resulting in a high CPC value (189 mmol·L^-1). Finally, the host-guest complexation between M1~M3 with the π-electron deficient bipyridinium-based cyclophane “blue-box” were further investigated, which shows that only M3 could perform host-guest complexation. From this interesting model, new insight into the relationship between molecular structure and supramolecular polymerization is discovered, which is important for creating tailor-made supramolecular polymeric materials.

Key words: supramolecular chemistry, quadruple hydrogen bonds, self-assembly, supramolecular polymer, macrocycles, host-guest interaction