Contribution a l'etude des especes africaines du genre Acioa Aubl.

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Polyamides based on a partially bio-based spirodiamine

In this study novel, fully and partially bio-based polyamides containing spiroacetal moieties in the backbone derived from bio-glycerol and bio-ethanol were prepared and characterized. The renewable diamine employed to obtain a series of polyamides was synthesized by means of thiolene click chemistry and therefore contains flexible thioether as well as rigid spiroacetal moieties. Two different chemical pathways for the polymerization were investigated and evaluated. The polymerization of polyamide salts proved to be the most promising method and therefore salt polymerization was applied in the synthesis of polyamides with aliphatic and aromatic di-carboxylic acids. Subsequently, the structure of the polymers was confirmed by Maldi-ToF analysis and additionally thermal and mechanical properties were investigated revealing T-g's between 24 and 80 degrees C and ductile materials with moduli between 1.0 and 1.5 GPa. Both semicrystalline and amorphous polyamides were thermally stable and therefore suitable for thermal processing. In the end, degradation studies were performed on the acetal containing polyamides which showed that the polymers were stable at pH 3 and higher

Een goed rapport is pas het halve werk, Reflectie op twee jaar Rekenkamercommissie Leiden-Leiderdorp [Februari 2021]

The Legitimacy and Effectiveness of Law & Governance in a World of Multilevel Jurisdiction

Exploring the substrate scope of Baeyer-Villiger monooxygenases with branched lactones as entry towards polyesters

Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts able to convert cyclic ketones to lactones by the insertion of oxygen. The aim of this study was to explore the substrate scope of several BVMOs with (biobased) cyclic ketones as precursors for the synthesis of branched polyesters.The product structure and the degree of conversion of several biotransformations was determined after conversions using self-sufficient BVMOs. Full regioselectivity towards the normal lactone of jasmatone and menthone was observed, while the oxidation of other substrates such as α,β-thujone and 3,3,5-trimethylcyclohexanone resulted in mixtures of regio-isomers. This exploration of the substrate scope of both established as well as newly discovered BVMOs towards biobased ketones contributes to the development of branched polyesters from renewable resources

The future of isosorbide as a fundamental constituent for polycarbonates and polyurethanes

Isosorbide is a biobased compound which could become in the near future an advantageous competitor of petroleum-derived components in the synthesis of polymers of different nature. When the reactivity of isosorbide is not enough, it can be successfully transformed into secondary building blocks, such as isosorbide bis(methyl carbonate), which provides extra functionalities for polymerization reactions with diols or diamines. The present review summarizes the possibilities for isosorbide as a green raw material to be used in the synthesis of polycarbonates and polyurethanes to obtain products of similar or enhanced properties to the commercial equivalents.This paper is a part of the research carried out within the VIPRISCAR project which has received funding from the Bio-Based Industries Joint Undertaking (JU) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 790440. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Bio-Based Industries Consortium

High performing immobilized Baeyer-Villiger monooxygenase and glucose dehydrogenase for the synthesis of ε-caprolactone derivative

The industrial application of Baeyer-Villiger monooxygenases (BVMOs) is typically hindered by stability and cofactor regeneration considerations. The stability of biocatalysts can be improved by immobilization. The goal of this study was to evaluate the (co)-immobilization of a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) with a glucose dehydrogenase (GDH) from Thermoplasma acidophilum for NADPH cofactor regeneration. Both enzymes were immobilized on an amino-functionalized agarose-based support (MANA-agarose). They were applied to the oxidation of 3,3,5-trimethylcyclohexanone for the synthesis of ε-caprolactone derivatives which are precursors of polyesters. The performances of the immobilized biocatalysts were evaluated in reutilization reactions with as many as 15 cycles and compared to the corresponding soluble enzymes. Co-immobilization proved to provide the most efficient biocatalyst with an average conversion of 83% over 15 reutilization cycles leading to a 50-fold increase of the biocatalyst yield compared to the use of soluble enzymes which were applied in a fed-batch strategy. TmCHMO was immobilized for the first time in this work, with very good retention of the activity throughout reutilization cycles. This immobilized biocatalyst contributes to the application of BVMOs in up-scaled biooxidation processes

Ruthenium-Catalysed Hydrogenation of Aromatic Ketones using Monodentate Phosphoramidite Ligands

A ruthenium pre-catalyst containing two equivalents of the bulky monodentate phosphoramidite 3,3’-dimethyl-PipPhos and one equivalent of a chiral diamine such as 1,2-diphenylethylenediamine or 1,2-diaminocyclohexane was used for the asymmetric hydrogenation of aromatic ketones. A range of substituted and unsubstituted aryl alkyl ketones was hydrogenated using only 0.1 mol% of this catalyst with full conversions and enantioselectivities up to 97%. The phosphoramidite and diamine ligands matched when both had the same configuration, i.e., S-phosphoramidite with S,S-diamine. In that case the product was obtained with high enantioselectivity and the R-configuration. The mismatched case produced the product in lower ee. The product configuration was determined by the configuration of the diamine ligand. A mechanistic proposal was made.

A Prospective Life Cycle Assessment (LCA) of Monomer Synthesis: Comparison of Biocatalytic and Oxidative Chemistry

Biotechnological processes are typically perceived to be greener than chemical processes. A life cycle assessment (LCA) was performed to compare the chemical and biochemical synthesis of lactones obtained by Baeyer-Villiger oxidation. The LCA is prospective (based on experiments at a small scale with primary data) because the process is at an early stage. The results show that the synthesis route has no significant effect on the climate change impact [(1.65 +/- 0.59)kgCO2 g(product)(-1) vs. (1.64 +/- 0.67)kgCO2 g(product)(-1)]. Key process performance metrics affecting the environmental impact were evaluated by performing a sensitivity analysis. Recycling of solvents and enzyme were shown to provide an advantage to the enzymatic synthesis. Additionally, the climate change impact was decreased by 71% if renewable electricity was used. The study shows that comparative LCAs can be used to usefully support decisions at an early stage of process development.</p