| Contents Notes |
Une sâerie de complexes áa base de titane porteurs de ligands aminodiols de diffâerentes configuration (mâelange de diastâerâeoisomáere, meso, racâemique ou chiral) ont âetâe synthâetisâes et caractâerisâes par diffâerentes techniques spectroscopiques. Ces complexes ont ensuite âetâe utilisâes comme amorceurs pour la polymâerisation par ouverture de cycles de diffâerents monomáeres hâetâerocycliques (L/rac-lactide, caprolactone, butyrolactone et trimâethyláene carbonate) via un mâecanisme de coordination-insertion. Tous les complexes se sont râevâelâes efficaces pour la polymâerisation des lactides que ce soit en solution áa 70ÀC ou en masse áa 130ÀC avec un bon contrãole. Lors de la polymâerisation du rac-lactide, le complexe porteur du ligand racâemique a permis d"obtenir un polylactide partiellement heterotactique, alors que tous les autres complexes n"ont conduit qu"áa des polymáeres atactiques. Tous les complexes se sont âegalement râevâelâes tráes actifs pour la polymâerisation de la caprolactone aussi bien en solution qu"en masse áa 70ÀC avec un bon contrãole. Des âetudes cinâetiques râealisâees en solution ont permis de mettre en âevidence un ordre cinâetique unitaire en monomáere. De bonnes activitâes ont âegalement âetâe obtenues pour la polymâerisation de la butyrolactone et du trimâethyláene carbonate. De plus, le bon contrãole de ce type de la polymâerisation a permis de synthâetiser des copolymáeres áa blocs du L/rac-lactide et de caprolactone. Enfin, la copolymâerisation alâeatoire de ces 2 monomáeres a permis de mettre en âevidence une râeactivitâe inversâee par rapport aux râeactions d'homopolymâerisation. A series of titanium isopropoxides complexes coordinated by enantiopure, racemic, meso and diastereomeric aminodiol ligands have been prepared and characterized by spectroscopic techniques. The complexes were tested as initiators for the ring opening polymerization (ROP) of cyclic esters such as L/rac-lactide, caprolactone, butyrolactone and trimethylene carbonate via coordination-insertion mechanism. In lactide polymerizations, all complexes showed significant activity both in solution at 70ÀC and in bulk at 130ÀC with a good control. The complex derived from rac-aminodiol ligand gave partially heterotactic polylactide in ROP of rac-lactide, whereas all other complexes yielded atactic polylactides. For caprolactone polymerizations, all complexes were found to be effective initiators under both solution and bulk conditions (up to 60% monomer conversion was reached within 10 min in bulk condition at 70ÀC), again with good control. Kinetic studies of ROP of lactides and caprolactone in solution conditions have been investigated and showed a first kinetic order in monomer. Significant activities were also observed for (ROP) of butyrolactone and trimethylene carbonate. Block copolymers of caprolactone and lactides were successfully synthesized with these catalytic systems by sequential polymerization techniques. The complexes were also tested as initiators for the production of random copolymers containing caprolactone and lactides and a reverse order of reactivity was observed between lactide and caprolactone compared to homopolymerization. |
