Synthesis of well-defined AB20-type star polymers with cyclodextrin-core by combination of NMP and ATRP

The synthesis of an AB(20)-type heteroarm star polymer consisting of a polystyrene arm and 20-arms of poly(methyl methacrylate) or poly(tert-butyl acrylate) was carried out using the combination of nitroxide-mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono-6-[4-(1'-(2 '',2 '',6 '',6-tetramethyl-1 ''-piperidinyloxy)ethyl)benzamido]-beta-cyclodextrin peracetate (1) to afford end-functionalized polystyrene with an acetylated beta-cyclodextrin (beta-CyD) unit (prepolymer 2) with a number-average molecular weight (M-n) of 11700 and a polydispersity (M-w/M-n) of 1.17. After deacetylation of prepolymer 2, the resulting polymer was reacted with 2-bromoisobutyric anhydride to give endfunctionalized. polystyrene with 20(2-bromoisobutyrol)s beta-Cyl), macroinitiator 4. The copper (I)-mediated ATRP of methyl methacrylate (MMA) and tert-butyl acrylate (tBA) was carried out using macroinitiator 4. The resulting polymers were isolated by SEC fractionation to produce AB(20)-type star polymers with a beta-CyD-core, 5. The well-defined structure of 5 with weight-average molecular weight (M-w)s of 13,500-65,300 and M-w/M-n's of 1.26-1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. (c) 2005 Wiley Periodicals, Inc.