Stereoregular diblock copolymers of syndiotactic polypropylene and polyesters: syntheses and self-assembled nanostructures

Abstract

Structurally well-defined stereoregular diblock copolymers composing of syndiotactic polypropylene (sPP) and polyester have been prepared using controlled ring-opening copolymerization of cyclic esters, including σ-caprolactone and DL-lactide, mediated by aluminum alkoxide end-capped sPP as the macroinitiator. The aluminum alkoxide end-capped sPP was generated by the in situ activation of hydroxyl-capped sPP with triethylaluminum (TEA). The hydroxy-capped sPP was prepared via the selective chain transfer reaction to TEA while inducing the syndiospecific polymerization of propylene in the presence of ansa-metallocene catalysts. The synthetic method not only offers high-yield production of the stereoregular block copolymers but also provides successful linking of the stereoregular polyolefins with an abundant variety of polymers as the second block. Moreover, the synthetic method offers effective control over the block chain length and molecular weight distribution; thus, the microphase separation of the resultant diblock copolymers generated well-ordered nanostructures as revealed by small-angle X-ray scattering. © 2009 American Chemical Society.