Polyrotaxane-based triblock copolymers synthesized via ATRP of N-isopropylacrylamide initiated from the terminals of polypseudorotaxane of Br end-capped pluronic 17R4 and β-cyclodextrins

Thermo-responsive polyrotaxane (PR)-based triblock copolymers were synthesized via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide initiated with self-assemblies made from a distal 2-bromoisobutyryl end-capped Pluronic 17R4 (PPO ₁₄-PEG ₂₄-PPO ₁₄) with a varying amount of β-cyclodextrins (β-CDs) in the presence of Cu(I)Cl/PMDETA at 25 °C in aqueous solution. The molecular structure was characterized by means of ¹H NMR, FTIR, WXRD, GPC, TGA and DSC analyses. About half of β-CDs are still entrapped on the Pluronic 17R4 chain while the number of incorporated NIPAAm monomers is nearly a double feed value in the resulting copolymers. The aggregate morphologies in aqueous solution were evidenced by TEM observations. A two-step thermo-responsive transition arising from a combination of a polypseudorotaxane middle block with poly(N-isopropylacrylamide) flanking blocks was also demonstrated by turbidity measurements. Given their thermo-responsive behavior in aqueous solution, these PR-based triblock copolymers show the potential to be used as smart materials for the controlled drug delivery systems, biosensors, and the like.