Poly(methyl methacrylate)-poly(caprolactone) AB and ABA block copolymers by combined ring-opening polymerization and atom transfer radical polymerization

Chemical modification of alpha-hydroxy,omega-isopropylestertelechelic iPrO-PCL-OH, 1, and alpha,omega-dihydroxytelechelic HO-PCL-OH, 4, poly(epsilon-caprolactone) (PCL), synthesized from ring-opening polymerization using La((OPr)-Pr-i)(3) or Sm(BH4)(3)(THF)(3), allows the synthesis of the corresponding alpha-bromoester end-funetionalized polymers iPrO-PCL-.Br, 2, and Br-PCL-Br, 5, respectively. This direct procedure consists in an esterification of the hydroxy group(s) of 1 and 4 using 2-bromoisobutyryl bromide. These bromopolyesters 2 and 5 have subsequently been used as macroinitiators to synthesize, via atom transfer radical polymerization of methyl methacrylate (MMA), the new set of di- and triblock polyester-polyacrylate copolymers PCL-b-PMMA, 3, and PMMA-b-PCL-b-PMMA, 6, respectively. All (co)polymers are well defined as characterized by NMR and size exclusion chromatography analyses. In addition, the thermal properties of copolymers 3 and 6 have been investigated by differential scanning calorimetry. The self-assembly of triblock PMMA-b-PCL-b-PMMA, 6, copolymers into nanoparticles has been investigated by dynamic light scattering, atomic force microscopy, and optical microscopy techniques.