Rotaxane‐type hyperbranched polymers from a crown ether host and paraquat guests containing blocking groups

Rotaxane‐type hyperbranched polymers are synthesized for the first time from A 2 B type semi‐rotaxane monomers formed in situ via complexation of bis( m ‐phenylene)‐32‐crown‐10 dimethanol ( 1 ) and two paraquat ω ‐ n‐ alkylenecarboxylic acid derivatives with tris( p‐t‐ butylphenyl)methylphenylalkylene stoppers ( 8 and 9) . Rotaxane and taco complexes exist in solutions of the hyperbranched polyesters in CD 3 CN/CDCl 3 as confirmed by NMR spectroscopy, but the taco complexes, which derive from non‐rotaxanated paraquat units, disappear in DMSO‐ d 6 . NMR spectroscopy indicates the portion of rotaxanes strongly interlocked by the environment (inner rotaxanes) is larger in HP1•9 , which has longer alkylene spacers, perhaps indicating a higher degree of polymerization. The molecular size increases upon formation of the hyperbranched polymers are confirmed by dynamic light scattering and by viscometry. As with covalent hyperbranched polymers a number of potential applications exist; the unique mechanically linked character and the presence of uncomplexed host and guest moieties foreshadow the use of such systems for their responses to external stimuli with the added benefit of providing molecular recognition sites useful as delivery vehicles. Use of other host‐guest motifs to form the semirotaxane A 2 B monomers is possible and complementary systems with higher binding constants will enable efficient syntheses of high molecular weight, mechanically linked hyperbranched polymers.