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. Polyrotaxane-based triblock copolymers were first synthesized via the ATRP of NIPAAm initiated with the self-assembly of a distal 2-bromoisobutyryl end-capped Pluronic 17R4 with a varying amount of α-CDs in the presence of CuCl/PMDETA at 25°C in aqueous solution. Those α-CDs entrapped on the polymer chain were then linked with hexamethylene diisocyanate to give rise to novel slightly cross-linked polyrotaxanes in DMF at 45°C.