Synthesis of Main-chain Hybrid Polypseudorotaxanes with Controlled Macrocycle Sequence

摘要

Polymers represent a ubiquitous class of compounds with diverse and desirable material properties. They are found in plastics, fibers, elastomers, coatings, adhesives, and composites. A major goal of polymer chemistry is to establish the relationship between polymer structure on the molecular level and the macroscale properties these materials exhibit. To this end, synthetic polymer chemists seek to vary the number and types of monomers that are the building blocks of different polymers, as well as the sequence and architecture in which these monomers are linked together. Traditional polymer architectures include linear and branched polymers composed of covalent linkages only. A relatively new polymer architectural class is the main-chain polyrotaxanes/polypseudorotaxanes (Figure 1), a subset of supramolecular polymers. Polyrotaxanes/polypseudorotaxanes incorporate mechanically linked subunits for which the connecting forces are noncovalent interactions;; typically macrocycles are penetrated by linear polymers. The distinguishing feature of polypseudorotaxanes are the lack of sterically bulky groups that act as stoppers to prevent dethreading of the macrocycles. The unique architectural characteristics of polyrotaxanes/pseudorotaxanes impart these materials with novel properties. However, the correlation between structure and macroscale properties is not well-established due to the synthetic challenge of making such polymers.