Novel triblock copolymers synthesized via radical telomerization of N-isopropylacrylamide in the presence of polypseudorotaxanes made from thiolated PEG and α-CDs

A protocol for the preparation of novel triblock copolymers comprising a polyrotaxane center block and outer blocks of poly(N-isopropylacrylamide) (PNIPAAm) as bulky stoppers was developed, in which N-isopropylacrylamide was allowed to telomerize in the presence of polypseudorotaxanes made from the self-assembly of thiol end-capped PEG with a varying amount of α-CDs under UV irradiation in aqueous solution. The molecular structure of the resulting copolymers was characterized in detail by 1H NMR, FTIR, XRD, TG and DSC analyses. It was demonstrated that the PNIPAAm blocks are successfully attached to the two terminals of the polypseudorotaxanes and each block having the minimum 7 NIPAAm units seems long and bulky enough to efficiently impede the dethreading of α-CDs from the PEG axle to give rise to the triblock polyrotaxane-containing copolymers.