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(ε‐caprolactone) (PCL) arms and 7 poly(acrylic acid) (PAA) arms with β‐cyclodextrin (β‐CD) as core moiety were synthesized by the combination of controlled ring‐opening 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)‐β‐CD as the multifunctional initiator in the presence of Sn(Oct) 2 at 125 °C. Subsequently, the hydroxyl end groups of CDSi‐SPCL were blocked by acetyl chloride. After desilylation of the tert ‐butyldimethylsilyl ether groups from the β‐CD core, 7 ATRP initiating sites were introduced by treating with 2‐bromoisobutyryl bromide, which further initiated ATRP of tert ‐butyl acrylate ( t BA) to prepare well‐defined A 14 B 7 multimiktoarm star copolymers [CDS(PCL‐P t BA)]. Their molecular structures and physical properties were in detail characterized by 1 H NMR, SEC‐MALLS, and DSC. The selective hydrolysis of tert ‐butyl ester groups of the P t BA 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).