Preparation of a daisy chain via threading-followed-by-polymerization

A daisy chain, a linear array of self-complementary (plerotopic) molecules linked together by mechanical bonds, was prepared by polyesterification of two complementary host-guest units based on the dibenzo-24-crown-8/1,2- bis(pyridinium)ethane recognition motif conveniently via "threading- followed-by-polymerization", an approach different from the formerly reported method, in which mechanically interlocked monomers were first prepared and then polymerized, used in the construction of this kind of polymers. It was characterized by various techniques including ¹H NMR, COSY, NOESY, GPC, TGA, dynamic laser light scattering (DLS), UV-vis, and viscosity. Its molecular weight M _n was 64 kDa with polydispersity of 1.5 as determined by GPC, indicating that 45 repeating units existed in a single polymer chain. Its hydrodynamic diameter in a dilute acetonitrile solution was about 250 nm as determined by DLS. These studies not only proved the successful fabrication of the desired daisy chain polymeric structure but also provided a convenient method to construct linear mechanically interlocked polymers, avoiding the tedious syntheses of AB-type mechanically interlocked monomers.