Synthesis and properties of a polyrotaxane network prepared from a Pd-templated bis-macrocycle as a topological cross-linker

Abstract

Polyrotaxane networks (PRNs) were synthesized by exploiting a Pd-templated bis-macrocycle as a topological cross-linker during radical polymerization of a vinyl monomer. The bis-macrocycle (9) was prepared by combining two macrocycles with a linear linker. Radical polymerization of 4-vinylpyridine in the presence of 9 and a catalytic amount of 2,2′-azobisisobutyronitrile (AIBN) yielded a gelled polymer. The addition of 4-tert-butylstyrene as a vinyl co-monomer to the polymerization system afforded a sufficiently stable gel as the PRN, clearly indicating that 4-tert-butylstyrene was successfully introduced as end-capping moieties of the trunk polymer. The swelling properties of the PRN were evaluated using several solvents. The topological structure and swelling properties of the PRNs were confirmed by a control experiment using a bis-acyclic pincer-type Pd complex (13) as a cross-linker.