Thesis of Xavier Mosca

Defense of thesis Xavier Mosca - laboratory UCCS

Abstract :

Chain shuttling copolymerization (CSP) is an innovative method enabling the synthesis of multiblock copolymers in a single step. Initially developed for the coordinative polymerization of olefins and conjugated dienes, this strategy has recently been applied to the ring-opening copolymerization (ROcoP) of cyclic esters.
In this context, amino(bis)phenol ligands were synthesized via a Mannich reaction and then used for the preparation of aluminum complexes, obtained from AlMe₃ and AlEt₃ precursors, followed by the addition of BnOH to obtain their alkoxide forms, with satisfactory yields. These complexes, with various side chains, allowed for tuning their reactivity and selectivity for the polymerization of L-lactide (L-LA) and ε-caprolactone (ε-CL).
The complexes were first tested for homopolymerization, then for the statistical copolymerization of the two monomers. Ligands with cyclohexyl pendant groups led to statistical copolymers with a slight predominance of LLA, while the presence of a bulky donor group on the side chain resulted in a stronger affinity for ε-CL. The complex with a pyridine-bearing side chain exhibited high selectivity for LLA, similar to an yttrium-based complex (OY₅(OCH(CH₃)₂)₁₃) and aluminum triisopropylate.
Nine new catalytic systems, capable of performing CSP of L-LA and ε-CL, were thus developed by combining initiators selective for L-LA with those more selective for ε-CL. This allowed significant modulation of the thermal properties of multiblock copolymers depending on the combinations of initiators and reaction conditions. Moreover, a CSP via transalkoxylation between two metals, Y and Al, was achieved for the first time, further expanding the application scope of this technique.

Keywords : Polylactide,Catalysis,Multi-block,Copolymer,Aluminium