Aggregation and thermal gelation of N-isopropylacrylamide based cucurbit[7]uril side-chain polypseudorotaxanes with low pseudorotaxane content

Abstract

N-Isopropylacrylamide (NIPAA) based cucurbit[7]uril (CB[7]) side-chain polypseudorotaxanes with low pseudorotaxane content were designed with the intention to emulate rod-coil block copolymers. In the polypseudorotaxanes, CB[7] pseudorotaxane units acted as rigid “rod segments” and the remaining polymer chain acted as the “soft-coils”. The length of soft-coil segments, which determines the aggregation behavior, can be easily tuned by changing the CB[7] pseudorotaxane content. The polypseudorotaxanes with much lower pseudorotaxane content demonstrate unique aggregation behavior, with a strong tendency for aggregation and thermal gelation. Their aggregation behavior and the formed hydrogels were studied with dynamic light scattering (DLS), and rheological and microscopic experiments. The mechanism of the unique aggregation behavior was also investigated.