Evaluation of the Effect of Chemical or Enzymatic Synthesis Methods on Biodegradability of Polyesters

International audienceThis work compares the biodegradability of polyesters produced by an esterification reaction between glycerol and oleic di-acid (D 18:1) issued from green chemical pathways, via either classical thermo-chemical methods, or an enzymatic method using the immobilized lipase of Candida antartica B (Novozym 435). An elastomeric polymer synthesized by enzymatic catalysis is more biodegradable than an elastomeric thermo-chemical polyester synthesized by a standard chemical procedure. This difference lies in percentage of the dendritic motifs, in values of the degree of substitution, and certainly in cross-links inducing an hyper-branched structure less accessible to the lipolytic enzymes in a waste treatment plant. However, when the elastomeric polymer synthesized by enzymatic catalysis is processed at high temperature as required for certain industrial applications, it presents an identical rate of biodegradation than the chemical polyester. The advantages of the thermo-chemical methods are greater speed and lower cost. Enzymatic synthesis appears be suited to producing polyesters, devoid of metallic catalysts, which must be used without processing at high temperature to keep a high biodegradability

Valuation of bio-based monomers applied to the synthesis of new polyesters

L’industrie des matériaux plastiques, tout comme la majorité des secteurs d’activité, connaît aujourd’hui un nouvel engouement pour les matières premières d’origine renouvelable. Cette tendance s’inscrit dans une démarche de développement durable, aspirant à la fois à trouver des alternatives aux ressources d’origine fossile, mais aussi à concevoir des produits plus respectueux de l’environnement. Parmi les composés issus du monde végétal, il existe non seulement des biopolymères, mais également de nombreuses molécules pouvant être mises à profit en tant que monomères. C’est dans ce contexte de valorisation de la biomasse que se positionne ce travail de thèse. De nouveaux polyesters bio-sourcés ont été développés à partir d’un diacide carboxylique d’origine naturelle : l’acide (Z)-octadéc-9-ènedioïque (D18:1). Cette molécule est obtenue par oxydation enzymatique de l’extrémité alkyle de l’acide oléique. Afin de mettre en application certains principes de la chimie verte, les polymérisations ont été menées parpolycondensation en masse et catalysées par des composés organométalliques. Divers diols ont été polymérisés avec le D18:1, notamment des diols aliphatiques, aromatiques, phénoliques ou encore certains dianhydrohexitols bio-sourcés. De plus, la modification chimique du D18:1 a permis de compléter cette étude par la synthèse de polyesters linéaires entièrement issus de l’acide oléique. L’évaluation des caractéristiques physicochimiques des ces nouveaux matériaux a été effectuée, notamment en termes de masse molaire, de propriétés thermiques et rhéologiques. Des tests préliminaires de biodégradation ont permis de dégager une tendance positive. Cette propriété est un atout qui permettrait de substituer certains plastiques issus de la pétrochimie.Nowadays, plastic industry is infatuated with renewable raw materials, as the majority of the business sectors. This trend is in line with the approach of sustainable development, by trying to find alternatives for fossil resources, and by designing more environmentally friendly products. Among compounds coming from vegetable source, there are not only biopolymers, but also numerous molecules which can be used as monomers. This PhD work takes position in this context of biomass valuation. Newbio-based polyesters were developed from a natural carboxylic diacid: the (Z)-octadec-9-enedioic acid(D18:1). This molecule is obtained by enzymatic oxidation of the alkyl end of oleic acid. To apply some green chemistry principles, polymers were synthesized by bulk step-growth polymerization, with organometallic catalysts. Miscellaneous diols were polymerized with D18:1, specifically aliphatic, aromatic and phenolic diols or some bio-based dianhydrohexitols. Furthermore, chemical modifications of D18:1allowed to synthesize linear polyesters entirely based on oleic acid. This new materials were chemically and physically characterized, in terms of molar mass, thermal and rheological properties. The main interest of most of synthesized polyesters is their biodegradability. This advantage could allow these materials to substitute those coming from petrochemistry, in some specific fields of application

Synthesis of Linear Polyesters from Monomers Based on 1,18-( Z )-Octadec-9-enedioic Acid and Their Biodegradability

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Novel aliphatic polyesters from an oleic acid based monomer. Synthesis, epoxidation, cross-linking and biodegradation

The synthesis of polymeric materials based on monomers from renewable feedstocks is a steadily growing field. New aliphatic polyesters derived from the 1,18-(Z)-octadec-9-enedioic acid (D18:1), a high oleic sunflower oil fatty acid derivative, and aliphatic diols of different molecular weight (from 1,3-propanediol to 1,12-dodecanediol) have been synthesized and characterized. The polymerization was undertaken by direct bulk polycondensation of a diacid with a diol, with or without a metal catalyst, leading to viscous liquid to solid semi-crystalline polyesters at room temperature, depending on the diol type. The molecular weights of polyesters ranged between 7000 and 20,000 g mol−1. The main attractive aspects of these polyesters are the renewable biomass origin of the diacid and the presence of double bonds on the polymer backbone (oleic acid derivative) allowing subsequent chemical modifications. The epoxidation of these double bonds was undertaken on the macromolecular chains to induce the photochemical cross-linking of the epoxide functions. Transparent and homogeneous cross-linked films were made by photo-polymerization of the epoxy units with less than 5% of extractible products. Enzymatic degradation of these polyesters (cross-linked) was poor over 8 weeks