Synthesis and characterization of polyrotaxane-based molecular nanotubes prepared from & alpha;-cyclodextrin/chlorinated polyethylene glycol complex end capped with 4-ethylaniline

An aqueous solution of chlorinated polyethylene glycol (Cl-PEG-Cl) and a-cyclodextrin (a-CD) was used to form inclusion complexes, which several a-CDs are threaded into the linear PEG chain and produced a so-called polypseudorotaxane (PPRx). By attaching 4-ethylaniline as the blocking agent to the chlorinated PEG chain ends, the complex will be stabilized, resulting in the formation of so-called polyrotaxane (PRx) (also known as molecular necklace). Finally, crosslinked aCD-based PRx with a tubular structure was formed via the condensation reactions between a-cyclodextrins and epichlorohydrin. Using concentrated NaOH solution, polymer chains were then removed from complexes, resulting in the so-called molecular tube (MT). This novel method led to the improvement in polyrotaxane conversion with less production steps and reduced materials overall costs. Resulting products in each section were characterized by H-1 and C-13 nuclear magnetic resonance spectroscopies (H-1-NMR and C-13-NMR), from which complex inclusion ratio and length of the nanotubes were estimated. XRD was also used to confirm tubular structure of the inclusion complexes.

Automated summary

An aqueous solution of chlorinated polyethylene glycol (Cl-PEG-Cl) and a-cyclodextrin (a-CD) was used to form inclusion complexes, which resulted in the formation of polypseudorotaxane (PPRx) and polyrotaxane (PRx) by stabilizing the complex with 4-ethylaniline as the blocking agent. Finally, crosslinked aCD-based PRx with a tubular structure was formed via condensation reactions between a-cyclodextrins and epichlorohydrin. The resulting products were characterized by H-1-NMR, C-13-NMR, and XRD spectroscopies.