One-Pot Synthesis of Lactide-Styrene Diblock Copolymers via Catalytic Immortal Ring-Opening Polymerization of Lactide and Nitroxide-Mediated Polymerization of Styrene
Résumé
An efficient, practical, and industrially relevant procedure for the production of polymer materials, in which a part of the oil-derived polyolefins has been replaced by a renewable, biodegradable, and biocompatible poly(lactide) block, is presented. Binary catalytic systems combining innocuous metals (yttrium, zinc, magnesium, or calcium) and bifunctional alcohols (acting as transfer agents) were developed to promote the immortal ring-opening polymerization of lactide directly in styrene. Up to 20 000 equivalents of lactide were polymerized (metal catalyst loading of 50-100 ppm) in a controlled fashion in the presence of 10-100 equivalents of a double-headed transfer agent to give as many end-functionalized poly(lactide) macromolecules that can be used eventually as macroinitiators for the controlled nitroxide-mediated polymerization of styrene. The specific use of the sterically shielded complex [BDI-iPr]Zn-N(SiMe3)2 ([BDI-iPr]=bis(diketiminate) ligand) allowed the efficient, catalytic, and controlled production of poly(lactide)-block-poly(styrene) materials in a one-pot, solvent-free sequential procedure, with nearly 100 % atom-efficiency.