Synthesis and Self-Assembly of Well-Defined Cyclodextrin-Centered Amphiphilic A14B7 Multimiktoarm Star Copolymers Based on Poly(ε-caprolactone) and Poly(acrylic acid)

Novel amphiphilic A(14)B(7) multimiktoarm star copolymers composed of 14 poly(epsilon-caprolactone) (PCL) arms and 7 poly(acrylic acid) (PAA) arms with beta-cyclodextrin (beta-CD) as core moiety were synthesized by the combination of controlled ringopening polymerization (CROP) and atom transfer radical polymerization (ATRP). 14-Arm star PCL homopolymers (CDSi-SPCL) were first synthesized by the CROP of CL using per-6-(tert-butyldimethylsilyl)-beta-CD as the multifunctional initiator in the presence of Sn(Oct)(2) at 125 degrees C. Subsequently, the hydroxyl end groups of CDSi-SPCL were blocked by acetyl chloride. After desilylation of the tert-butyl-dimethylsilyl ether groups from the fl-CD core, 7 ATRP initiating sites were introduced by treating with 2-bromoisobutyryl bromide, which further initiated ATRP of tert-butyl acrylate (tBA) to prepare well-defined A(14)B(7) multimiktoarm star copolymers [CDS(PCL-PtBA)I. Their molecular structures and physical properties were in detail characterized by H-1 NMR, SEC-MALLS, and DSC. The selective hydrolysis of tert-butyl ester groups of the PtBA block gave the amphiphilic A(14)B(7) multimiktoarm star copolymers [CDS(PCL-PAA)]. These amphiphilic copolymers could self-assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2961-2974,2010