Slightly Cross‐Linked Polyrotaxanes Made by Linking α‐Cyclodextrins Entrapped in Polyrotaxanes Using Hexamethylene Diisocyanate

In this study polyrotaxane (PR)‐based triblock copolymers were first synthesized via the atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide initiated with the self‐assembly of a distal 2‐bromoisobutyryl end‐capped Pluronic 17R4 with a varying amount of α‐cyclodextrins (α‐CDs) in the presence of CuCl/PMDETA at 25°C in aqueous solution. The α‐CDs entrapped on the copolymer chain were then linked with hexamethylene diisocyanate to give rise to novel slightly cross‐linked polyrotaxanes (SCPRs) in DMF at 45°C. The structures of the PR‐based triblock copolymers and SCPRs were characterized by ¹H NMR, ¹³C CP/MAS, GPC and TGA analyses. The number‐average molecular weight of the resulting SCPRs was nearly three and five times of their precursor after linking with a low polydispersity index range of 1.08–1.28. The thermo‐responsive transition of both PR‐based supramolecular polymers in aqueous solution was demonstrated by turbidity measurements and the self‐aggregated morphologies were also evidenced by TEM observations.