Synthesis and Characterization of Novel Resorcinarene-Centered Amphiphilic Star-Block Copolymers Consisting of Eight ABA Triblock Arms by Combination of ROP, ATRP, and Click Chemistry

Novel amphiphilic eight-arm star triblock copolymers, star poly(P.-caprolactone)-block-poly(acrylic acid)-block-poly(epsilon-caprolactone)s (SPCL-PAA-PCL) with resorcinarene as core moiety were prepared by combination of ROP, ATRP, and click reaction strategy. First, the hydroxyl end groups of the predefined eight-arm SPCLs synthesized by ROP were converted to 2-bromoesters which permitted ATRP of tert-butyl acrylate (tBA) to form star diblock copolymers: SPCL-PtBA. Next, the bromide end groups of SPCL-PtBA were quantitatively converted to terminal azides by NaN3, which were combined with presynthesized alkyne-terminated poly(epsilon-caprolactone) (A-PCL) in the presence of Cu(I)/N,N,N',N '',N ''-pentamethyldiethylenetriamine in DMF to give the star triblock copolymers: SPCL-PtBA-PCL. H-1 NMR, FTIR, and SEC analyses confirmed the expected star triblock architecture. The hydrolysis of tert-butyl ester groups of the poly(tert-butyl acrylate) blocks gave the amphiphilic star triblock copolymers: SPCL-PAA-PCL. These amphiphilic star triblock copolymers could self-assemble into spherical micelles in aqueous solution with the particle size ranging from 20 to 60 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. (c) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2905-2916, 2009