New strategies for the preparation of high-perfomance bio-based polymers

Nowadays there is a great interest to substitute petroleum-derived polymers with more sustainable materials. In this thesis the preparation of monomers, polymers and copolymers from renewable resources was carried out, following two strategies. The first one consisted in developing new routes to obtain the traditional polymers from biomass instead that from petroleum. Then, the synthesis of p-toluic acid (the terephthalic acid (TPA) precursor, and monomer for polyethylene terephthalate (PET)) from natural molecules (acrylic and sorbic acids) was set up by exploiting a Diels-Alder (DA) reaction. The developed strategy contributed to a more sustainable production of TPA, and, therefore, of a 100% bio-PET. The second strategy was based on exploiting monomers deriving from biomass to get new polymeric structures. Starting from vanillic acid, a monomer from natural resources, the synthesis of polyethylene vanillate, an homopolymer whose melting and glass transition temperatures are close to those of PET, was set up. To reduce its brittleness, random copolymers with ϵ-polycaprolactone or polyricinoleic acid were prepared; new possible antibacterial functionalities were introduced by ricinoleic acid functionalities. The preparation of copolymers was furthermore studied by considering DA reactions between furans (obtainable from natural resources) and maleimides: a copolymer was prepared by exploiting the tendency by DA adducts located within monomers structures to break over 100°C and to recombine at lower temperatures: the ability to associate and dissociate in a reversible manner can be used to produce innovative self-mending materials. Finally, a compound deriving from vegetal oil biorefinery (dihydroxyacetone) was exploited for obtaining innovative and bio-based polycarbonates and polyesters. In conclusion, strategies to get a 100% bio-PET, new bio-polymers that can substitute PET even with advanced functionalities, innovative bio-copolymers for self-mending materials and new polyesters and polycarbonates making the most of oil biorefinery byproducts were studied.Nei tempi recenti si è sviluppato un grande interesse nel sostituire polimeri derivati dal petrolio con materiali più sostenibili. In questa tesi si è studiata la possibilità di ottenere da biomassa monomeri, polimeri e copolimeri, seguendo due strategie di sintesi. La prima è consistita nell’ottenimento da biomassa di polimeri tradizionali attualmente ricavati da petrolio. In particolare, la sintesi dell’acido p-toluico (il precursore dell’acido tereftalico (TPA) e, quindi, del polietilene tereftalato (PET)) è stata messa a punto partendo da molecole naturali (dagli acidi sorbico ed acrilico) tramite reazione di Diels-Alder (DA). Ciò ha contribuito ad una produzione più sostenibile del TPA e, pertanto, di un PET bio al 100%. La seconda strategia ha sfruttato monomeri da biomassa per l’ottenimento di nuove strutture polimeriche. Da acido vanillico (un monomero da fonti naturali) è stata messa a punto la sintesi del polietilene vanillato, un omopolimero le cui temperature di fusione e transizione vetrosa sono vicine a quelle del PET. Al fine di ridurne la fragilità, sono stati preparati polimeri statistici con unità di ϵ-policaprolattone o di acido poliricinoileico, dalle cui funzionalità sono state introdotte nuove possibili proprietà antibatteriche. La preparazione di copolimeri è stata inoltre studiata tramite reazioni DA fra furani (ottenibili da fonti naturali) e malemmidi; un copolimero è stato preparato sfruttando la tendenza degli addotti DA presenti all’interno della struttura monomerica di rompersi sopra 100°C e di ricombinarsi a temperature inferiori; l’abilità di associarsi e dissociarsi reversibilmente può essere usata per produrre materiali autoriparanti innovativi. Infine un composto proveniente dalla bioraffineria degli oli vegetali (diidrossiacetone) è stato utilizzato per ottenere bio-policarbonati e bio-poliesteri. Concludendo, sono state studiate strategie per ottenere un PET 100% bio, nuovi bio-polimeri che possano sostituirlo addirittura con proprietà avanzate, bio-polimeri per materiali autoriparanti e poliesteri e policarbonati sfruttando al meglio sottoprodotti della bioraffineria degli oli vegetali

Sintesi e caratterizzazione di nuovi biopoliesteri aromatici a base di resorcinolo

Il lavoro di tesi si inserisce in un contesto di ricerca molto attuale, che studia la preparazione di nuovi materiali polimerici ad elevate prestazioni e derivabili da fonti rinnovabili. Partendo dal resorcinolo, una molecola che può essere ottenuta da biomassa, e dall’etilene carbonato sono state ottimizzate la sintesi e la purificazione di un diolo, l’1,3-bis(2-idrossietossi)benzene (HER), senza l’impiego di solventi e con l’utilizzo di modeste quantità di catalizzatore. L’HER è conosciuto in letteratura ma è poco studiato e non viene attualmente impiegato come monomero. In questo lavoro L’HER è stato polimerizzato in massa con una serie di diacidi (alcuni derivati da biomassa, altri provenienti da fonti fossili) sia di natura alifatica (lineari e ciclici) che di natura aromatica. Sono state analizzate la struttura chimica e le proprietà termiche dei nuovi poliesteri, in modo da definire correlazioni fra struttura e prestazioni finali. E’ stata infine messa a punto una procedura one-pot per la preparazione dei suddetti poliesteri; essa prevede la sintesi diretta dei polimeri senza lo stadio intermedio di purificazione dell’HER

A NEW APPROACH TO THE SYNTHESIS OF MONOMERS AND POLYMERS INCORPORATING FURAN/MALEIMIDE DIELS-ALDER ADDUCTS

The Diels-Alder reaction between furan and maleimide moieties is a well-known and widely used strategy to build bio-based macromolecular structures with peculiar properties. The furan-maleimide adducts are thermally reversible because they can be broken above about 120\ub0C and recombined at lower temperatures. At the moment only the monomers exhibiting the furan or the maleimide moieties on their extremity are used in order to get linear or cross-linked polymeric structures. The innovative idea described here consists in using a monomer bearing two carboxylic acidic groups on its extremities and a furan-maleimide Diels-Alder adduct within its structure. This monomer can give rise to classical polycondensation reactions leading to polymers. These polymers (which are polyesters in the present case) can be broken at high temperatures in correspondence of the furane-maleimide Diels-Alder adduct leading to segments exhibiting furan or maleimide moieties at their extremities, which at lower temperature recombine leading to random or block copolymers

A Sustainable Route to a Terephthalic Acid Precursor

A new synthetic pathway for the production of p-toluic acid has been developed starting from reagents derived from renewable resources. A Diels-Alder reaction between sorbic and acrylic acids is followed by a combined dehydrogenation/ decarboxylation process, providing p-toluic acid in high yields. This route permits to use milder conditions compared to other Diels-Alder approaches reported in the literature, and therefore can contribute to a more sustainable terephthalic acid production

Insights into the synthesis of PEF from FDCA: steps toward environmental and food safety excellence in packaging applications

Poly(ethylene 2,5-furandicarboxylate) (PEF) is considered today as a very promising biobased polymer for packaging applications. The main reason lies in its extraordinary barrier properties: oxygen permeability in PEF is reduced by a factor of about 10 with respect to poly(ethylene terephthalate) (PET) (1). In terms of the synthesis of PEF, scientific literature describes synthetic procedures based on the transesterification of the dimethylester of the 2,5-furandicarboxylic acid (2,3,4). This research, instead, aims at studying the possibility of a practical and profitable synthetic route of PEF starting from the 2,5-furandicarboxylic acid. In this respect two catalysts, zinc acetate (ZnAcO) and aluminum acetylacetonate (Al(acac)3), chosen for their compatibility with food contact applications and for featuring a potentially reduced environmental impact, were investigated. The synthesis was performed by using tight reaction conditions: low excess of diol and short reaction time. Indeed, the use of high amount of glycol could lead to the ether-bridges (DEG) formation, which significantly reduces the extremely valuable barrier performances of PEF; high polymerization times lead to material yellowing, indicating the occurrence of by-side reactions. Different catalyst amounts and addition times were tested and the obtained polymers were characterized in terms of inherent viscosity, color (absorbance at 400 nm), and diethylene glycol content, as summarized in Table 1. Since titanium (IV) butoxide (TBT) is the most used catalyst in the PEF syntheses, PEF samples prepared with it were reported as a reference for the present study. Results show that ZnAcO and Al(acac)3 are very promising catalysts for the PEF polymerization from FDCA, because the use of ZnAcO allows them to reach relatively high inherent viscosity in the usual polymerization procedure, while the use of Al(acac)3 leads to materials characterized by very low yellowing. In this case, the moderate molecular weight obtained for aluminum-based PEF was overcome by a final step of solid state polymerization (SSP), which increases the viscosity from 0.25 to 0.39 dL/g in just 3 days. Finally, the obtained amorphous PEF samples result filmable and therefore suitable for the manufacturing of various packaging articles

A new approach to the synthesis of monomers and polymers incorporating furan/maleimide Diels-Alder adducts

The Diels-Alder reaction between furan and maleimide moieties is a well-known and widely used strategy to build bio-based macromolecular structures with peculiar properties. The furan-maleimide adducts are thermally reversible because they can be broken above about 120\ub0C and recombined at lower temperatures. At the moment only the monomers exhibiting the furan or the maleimide moieties on their extremity are used in order to get linear or cross-linked polymeric structures. The innovative idea described here consists in using a monomer bearing two carboxylic acidic groups on its extremities and a furan-maleimide Diels-Alder adduct within its structure. This monomer can give rise to classical polycondensation reactions leading to polymers. These polymers (which are polyesters in the present case) can be broken at high temperatures in correspondence of the furane-maleimide Diels-Alder adduct leading to segments exhibiting furan or maleimide moieties at their extremities, which at lower temperature recombine leading to random or block copolymers

Resorcinol: A potentially bio-based building block for the preparation of sustainable polyesters

Potentially bio-based aromatic polyesters with a kinked structure based on resorcinol have been successfully prepared. The process involves an optimized reaction between resorcinol and ethylene carbonate: the diol thus obtained was polymerized with several aliphatic and aromatic dicarboxylic acids. The chemical structure and the thermal properties of the new polyesters were analysed in order to find correlations between structure and properties. All the polymers present a high thermal stability and are mainly amorphous, with a wide range of glass transition temperatures, according to the diacid structures. On the basis of the results it is clear that resorcinol, which can be derived from renewable resources, is a potential bio-based aromatic monomer, suitable to prepare amorphous polyesters containing 1,3 substituted aromatic moieties, for coating and packaging applications