Développement de nouveaux polyesters par catalyse organométallique et enzymatique

In the context of sustainable development, new biobased and aliphatic macromolecular architectures were synthesized from building blocks that can be obtained by fermentation routes using carbon sources from the biomass. First, several aliphatic copolyesters were synthesized in bulk from short dicarboxylic acids (such as succinic and adipic acids) and diols (such as 1,3-propanediol, 1,4-butanediol and 2,3-butanediol) by organometallic catalysis using an effective titanium-based catalyst. In a second time, similar macromolecular architectures were synthesized by an enzymatic process in solution using Candida antarctica lipase B as catalyst. The influence of the alkyl chain length and the structure of monomers on their reactivity toward the lipase were particularly discussed. In the third and last part, new macromolecular architectures based on hydroxytelechelic oligomers of a bacterial polyester: poly((R)-3-hydroxybutyrate) (PHB), such as poly(ester-ether-urethane)s and copolyesters, were obtained by either chain-coupling using a diisocyanate, or organometallic and enzymatic transesterification, respectively.These studies permitted to determine a close relationship between the effect of the building blocks structure integrated in the final macromolecular architectures and the intrinsic properties, such as the crystalline structure, the thermal stability and the thermal and optical properties, of these polymers. In addition, the great potential of the lipase-catalyzed synthesis of polyesters and the use of PHB oligomers for developing new high performance materials has been clearly established.Dans un contexte du développement durable, de nouvelles architectures macromoléculaires biosourcées ont été synthétisées à partir de synthons (diacides et diols) pouvant être obtenus par voies fermentaires à partir de sources carbonées issues de la biomasse. Dans un premier temps, différents copolyesters aliphatiques ont été synthétisés en masse, à l’aide d’un catalyseur organométallique à base de titane, à partir de diacides (acides succinique et adipique) et de diols (1,3-propanediol, 1,4-butanediol et 2,3-butanediol) courts. Dans un deuxième temps, des architectures macromoléculaires similaires ont été obtenues par catalyse enzymatique en solution à l’aide de la lipase B de Candida antarctica. L’influence de la longueur et de la structure des monomères sur leur réactivité en présence de la lipase a été particulièrement étudiée. Dans un troisième et dernier temps, des architectures macromoléculaires à base d’oligomères hydroxytéléchéliques d’un polyester bactérien : le poly((R)-3-hydroxybutyrate) (PHB)tels que des poly(ester-éther-uréthane)s et des copolyesters ont été obtenues soit par couplage de chaîne à l’aide d’un diisocyanate, ou par transestérification organométallique et enzymatique. Ces études ont permis d’analyser en détail l’effet de l’addition des synthons biosourcés dans les architectures macromoléculaires et notamment sur la structure cristalline, la stabilité thermique et les propriétés thermiques et optiques de ces polymères. De plus, le grand potentiel de la catalyse enzymatique pour la synthèse de polyesters et celui de l’utilisation d’oligomères de PHB pour l’élaboration de nouveaux matériaux performants ont pu être largement démontrés

Enzymatic Synthesis of a Bio-Based Copolyester from Poly(butylene succinate) and Poly((<i>R</i>)‑3-hydroxybutyrate): Study of Reaction Parameters on the Transesterification Rate

The enzyme-catalyzed synthesis of fully biobased poly­(3-hydroxybutyrate-<i>co</i>-butylene succinate) (poly­(HB-<i>co</i>-BS)) copolyesters is reported for the first time. Different Candida antarctica lipase B (CALB)-catalyzed copolyesters were produced in solution, via a one-step or a two-step process from 1,4-butanediol, diethyl succinate, and synthesized telechelic hydroxylated poly­(3-hydroxybutyrate) oligomers (PHB-diol). The influence of the ester/hydroxyl functionality ratio, catalyst amount, PHB-diol oligomer chain length, hydroxybutyrate (HB) and butylene succinate (BS) contents, and the nature of the solvent were investigated. The two-step process allowed the synthesis of copolyesters of high molar masses (<i>M</i>_n up to 18 000 g/mol), compared to the one-step process (<i>M</i>_n ∼ 8000 g/mol), without thermal degradation. The highest molar masses were obtained with diphenyl ether as solvent, compared with dibenzyl ether or anisole. During the two-step process, the transesterification rate between the HB and BS segments (i) increased with increasing amount of catalyst and decreasing molar mass of the PHB-diol oligomer, (ii) decreased when anisole was used as the solvent, and (iii) was not influenced by the HB/BS ratio. Tendencies toward block or random macromolecular architectures were observed as a function of the reaction time, the PHB-diol oligomer chain length, and the chosen solvent. Immobilized CALB-catalyzed copolyesters were thermally stable up to 200 °C. The crystalline structure of the poly­(HB-<i>co</i>-BS) copolyesters depended on the HB/BS ratio and the average sequence length of the segments. The crystalline content, <i>T</i>_m and <i>T</i>_c decreased with increasing HB content and the randomness of the copolymer structure

Tailoring the structure, morphology, and crystallization of isodimorphic poly(butylene succinate-ran-butylene adipate) random copolymers by changing composition and thermal history

Poly(butylene succinate-ran-butylene adipate) random copolymers (PBSA) were prepared by melt polycondensation in a wide composition range. Polarized light optical microscopy (PLOM) was employed to observe their superstructural morphology while their thermal and structural properties were studied by differential scanning calorimetry (DSC) and in situ synchrotron Xray diffraction at wide and small angles (WAXS and SAXS). The morphological study revealed negative spherulitic superstructures with (PBS-rich) and without (PBA-rich) ring band patterns depending on composition. The crystallization temperature, melting temperature, and related enthalpies display a pseudoeutectic behavior as a function of composition. WAXS studies demonstrated that these random copolymers are isodimorphic, as their unit cell parameters are composition dependent and switch from PBS-like unit cells to \u3b2-PBA-like unit cells around the pseudoeutectic point. For PBA-rich compositions, the inclusion of butylene succinate units in the copolymer selectively promotes the formation of the orthorhombic \u3b2-polymorph, instead of the commonly observed monoclinic \u3b1-structure. The pseudoeutectic point is located around the 50:50 and 40:60 compositions and is characterized by a remarkable rate-dependent cocrystallization. Parallel DSC, SAXS, and WAXS results for these intermediate compositions show that depending on the cooling rate employed, the materials can exhibit single- or double-crystalline character either upon cooling or during subsequent heating. The structure, morphology, and properties of these versatile random copolymers can be tailored by composition and thermal history

Tailoring the Structure, Morphology, and Crystallization of Isodimorphic Poly(butylene succinate-<i>ran</i>-butylene adipate) Random Copolymers by Changing Composition and Thermal History

Poly­(butylene succinate-<i>ran</i>-butylene adipate) random copolymers (PBSA) were prepared by melt polycondensation in a wide composition range. Polarized light optical microscopy (PLOM) was employed to observe their superstructural morphology while their thermal and structural properties were studied by differential scanning calorimetry (DSC) and <i>in situ</i> synchrotron X-ray diffraction at wide and small angles (WAXS and SAXS). The morphological study revealed negative spherulitic superstructures with (PBS-rich) and without (PBA-rich) ring band patterns depending on composition. The crystallization temperature, melting temperature, and related enthalpies display a pseudoeutectic behavior as a function of composition. WAXS studies demonstrated that these random copolymers are isodimorphic, as their unit cell parameters are composition dependent and switch from PBS-like unit cells to β-PBA-like unit cells around the pseudoeutectic point. For PBA-rich compositions, the inclusion of butylene succinate units in the copolymer selectively promotes the formation of the orthorhombic β-polymorph, instead of the commonly observed monoclinic α-structure. The pseudoeutectic point is located around the 50:50 and 40:60 compositions and is characterized by a remarkable rate-dependent cocrystallization. Parallel DSC, SAXS, and WAXS results for these intermediate compositions show that depending on the cooling rate employed, the materials can exhibit single- or double-crystalline character either upon cooling or during subsequent heating. The structure, morphology, and properties of these versatile random copolymers can be tailored by composition and thermal history