Synthesis and characterization of block copolymers comprising a polyrotaxane middle block flanked by two brush-like PCL blocks

A polyrotaxane was prepared via atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) initiated by a polypseudorotaxane self-assembled from a distal 2-bromoisobutyryl end-capped poly(ethylene glycol) (BriB-PEG-iBBr) with alpha-cyclodextrins (alpha-CDs). Then it was used to initiate bulk ring-opening polymerization (ROP) of epsilon-caprolactone (CL) to give block copolymers comprising a polyrotaxane middle block flanked by two brush-like polycaprolactone (PCL) blocks. The structure of both the polyrotaxane and its CL derivatives was characterized by H-1 NMR, GPC, FT-IR, XRD, DSC and TG analyses. These polyrotaxane-derived block brush-like copolymers can be cast into self-standing films from CH2Cl2 and self-assemble into nano-sized particles in THF as well. Furthermore they can melt at round 60 degrees C, showing the potential for melt-processing.