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 Pluronie 17R4 with a varying amount of a-cyclodextrins （a-CDs） in the presence of CuCI/PMDETA at 25 ℃ in aqueous solution. The a-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 ℃. The structures of the PR-based triblock copolymers and SCPRs were characterized by 1H NMR, 13C CP/MAS, GPC and TGA analy- ses. 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.
Thermo-responsive polyrotaxane （PR）-based triblock copolymers were synthesized via the atom transfer radical polymeriza- tion （ATRP） of N-isopropylacrylamide initiated with self-assemblies made from a distal 2-bromoisobutyryl end-capped Plu- ronic 17R4 （PPOI4-PEG24-PPOI4） with a varying amount of β-cyclodextrins （β-CDs） in the presence of Cu（I）C1/PMDETA at 25 ~C in aqueous solution. The molecular structure was characterized by means of ~H NMR, FTIR, WXRD, GPC, TGA and DSC analyses. About half of [3-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.
LI Shuo WANG Jin GAO Peng YE Lin ZHANG AiYing FENG Zeng-Guo
