Construct of nano micelles based on miktoarm star copolymer with a cyclodextrin core and their inclusion properties

A star-shaped polymer, MPEG-CD-PNIPAM_x, which possesses the lower critical solution temperature(LCST), was designed and synthesised. MPEG-CD-PNIPAM_x was composed of a β-cyclodextrin(β-CD) moiety as the core, one methoxypolyethylene glycol(MPEG) chain and 2-4 poly(N-isopropylacrylamide)(PNIPAM) chains as double hydrophilic arms. The structure of MPEG-CD-PNIPAM_x was characterized by ¹H NMR, ¹³C NMR and the molecular weight and molecular weight distribution were measured by size exclusion chromatography/multi-angle laser light scattering(SEC/MALLS) technology. The number of PNIPAM arm was determined by integrating the peaks of ¹H NMR spectrum. When the temperature of the aqueous solution of MPEG-CD-PNIPAM_x raises over the LCST(37°C), the star shaped molecule becomes amphiphilic, and then self-assemble into micelles with PNIPAM as the core layer, β-CD and MPEG as the shell layer. The fluorescence spectroscopy of MPEG-CD-PNIPAM_x and its micelles in pyrene aqueous solution reveal that the micells can include hydrophobic guest molecule at two sites: the cavity of β-CD and the hydrophobic core of the micelle.