Polyhydroxyalkanoates for advanced applications

Polyhydroxyalkanoates (PHAs) are a group of biobased, biodegradable and biocompatible polyesters, synthetized, through fermentation processes, by bacterial enzymes from various feedstock, e.g. agricultural wastes, that represent a promising alternative to currently used petroleum-based polymers. Among various produced PHAs, poly(3-hydroxybutyrate) (PHB) and the copolymer poly(3-hydroxybutyarte-co-3-hydroxyvalerate-co-4-hydroxyvalerate) (PHBVV) are nowadays intensively studied. Such polyesters are intriguing candidates as fully biobased and biodegradable polymeric matrix, which can be reinforced to obtain composites with enhanced thermal and mechanical properties. Using a novel approach, water-suspended micro-fibrillated cellulose (MFC) was dispersed into a PHA matrix through thermo-mechanical mixing by using a suitable polymeric dispersing agent. SEM images confirms obtainment of good dispersion and encourage further investigation. Furthermore, considering biocompatibility of PHAs, realization of PHB and PHBVV scaffolds for tissue engineering, filled with osteoinductive inorganic particles, were prepared. Preliminary in vitro investigations showed promising results and further analyses are currently ongoing. To improve and tune intrinsic excellent PHAs properties, and possibly extend polyesters applications, post-polymerization macromolecular chains modifications were attempted. After a PHB and PHBVV fully characterization by conventional chromatographic, thermal and spectroscopic analyses, a more complete characterization has been achieved by end-groups analyses through a herein proposed new 19F-NMR method, which allows to overcome typical disadvantages and drawbacks of traditional techniques. The 19F-NMR method reveled to be a simple and fast analytical tool for characterizing PHB derivatives and planning further reactions to obtain useful PHB-based macromonomers, as the herein presented UV-sensible PHB-based segments. Following the successful utilization of PHB-based cross-linking agent mixed with a liquid commercial methacrylate monomer in stereolithography 3D printing, demonstrating the real possible application of the synthesized material, a new green solvent-free preparation procedure was established. In this dissertation, a wide range of possible methodologies for PHAs properties modification have been proposed and all prepared materials can be envisioned in several various technological applications.