Michel Duc

One-pot synthesis of lactide-styrene diblock copolymers via catalytic immortal ring-opening polymerization of lactide and nitroxide-mediated polymerization of styrene.

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relevant procedure for the production of polymer materials, in which a part of the oil-derived polyolefins has been replaced by a renewable, biodegradable, and biocompatible poly(lactide) block, is presented.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(SiMe(3))(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.

Evolution of the partition coefficients of peroxide initiators during the synthesis of high-impact polystyrene

Abstract The partition coefficient K of commercially available peroxide initiators between polystyrene (PS) and polybutadiene (PB) phases during the synthesis of high-impact PS is investigated with model systems. Influences of styrene conversion and peroxide initiator concentration on K are studied for two different PBs. It is shown that K varies linearly with conversion, exhibits a logarithmic behaviour according to the peroxide initiator concentration, and is influenced by the microstructure of PB. Nevertheless, these effects are weak. For any peroxide initiator family studied, i.e., percarbonate, perester, and perdiketal, the values of K are close to 1, showing that peroxide initiators are evenly distributed between the PS and PB phases, before the phase inversion.