Synthesis and characterization of polyrotaxanes made from α-CDs threaded onto triblock copolymers with PEG as a central axle and flanked by two low molecular weight polystyrenes as outer stoppers

A study has been conducted on the synthesis and characterization of a kind of novel polyrotaxanes comprising α-cyclodextrins (α-CDs) threaded on triblock copolymers with poly(ethylene glycol) (PEG) as a central axle and flanked by two low molecular weight polystyrenes as outer stoppers. Styrene was allowed to telomerize with polypseudorotaxanes as chain transfer agents made from the self-assembly of a distal thiol-capped PEG with a varying amount of α-CDs in the presence of a redox initiation system at 40°C in aqueous solutions. The resulting polyrotaxanes were characterized in detail by ¹H-NMR, FTIR, XRD, TG and DSC analyses. The findings from the study demonstrated that the low molecular weight polystyrenes were successfully attached to two axle terminals of polypseudorotaxanes, and the number of α-CDs threaded onto the PEG backbone was tunable by varying its molar feeding ratio to some extent, while the polymerization degree of PS nearly remained constant in this radical telomerization process.