Blends of synthetic atactic poly(3-hydroxybutyrate) (a-PHB) with a natural bacterial isotactic copolymer of 3-hydroxybutyrate with 3-hydroxyvalerate (PHBV) containing 10 mol % of 3HV units were prepared using a simple casting procedure. In the range of compositions explored (10−50% a-PHB), blends of bacterial PHBV and synthetic atactic a-PHB were miscible in the melt and solidified with spherulitic morphology. The influence of a-PHB content on the thermal and mechanical properties of the blends was evaluated. The degree of crystallinity decreased with increasing content of a-PHB in the film samples, and the elongation at break for a sample containing 50% of a-PHB was 30-fold that of pure PHBV. Degradation experiments, both hydrolytic (pH = 7.4, T = 70 °C) and enzymatic (PHB-depolymerase A from Pseudomonas lemoignei, Tris-HCl buffer (pH = 8), T = 37 °C), were performed for both polymers and polymer blends. The rate of enzymatic degradation of the blends was higher than that of PHBV and increased with a-PHB content in the blends studied, whereas pure a-PHB did not biodegrade under these conditions. 3-Hydroxybutyric acid and its dimer were identified by HPLC as biodegradation products of both pure PHBV and its blends with a-PHB. Higher oligomers up to heptamer were detected as degradation products of the blends by APCI-MS and ESI-MS.

This review focuses on the polyesters such as polylactide and polyhydroxyalkonoates, as well as polyamides produced from renewable resources, which are currently among the most promising (bio)degradable polymers. Synthetic pathways, favourable properties and utilisation (most important applications) of these attractive polymer families are outlined. Environmental impact and in particular (bio)degradation of aliphatic polyesters, polyamides and related copolymer structures are described in view of the potential applications in various fields.

Sequence distribution and chemical structure of mass-selected macromolecules of poly(3hydroxybutyrate-co-3-hydroxyvalerate), PHBV, biopolyester macroinitiator obtained by partial alkaline depolymerization of natural PHBV containing 5 mol % of HV units was determined by electrospray ionization multistage mass spectrometry (ESI-MS n ). On the basis of the ESI-MS n studies of PHBV individual oligomers, the microstructure of this bacterial copolyester was assessed, starting from dimer up to the oligomer containing 22 repeat units, and the results obtained were compared with those described previously for other "soft" ionization MS techniques.

The use of biobased plastics is of great importance for many applications. Blending thermoplastic polylactide (PLA) with polyhydroxyalkanoate (PHA) enables the formulation of a more mechanically powerful material and this enables tailored biodegradation properties. In this study we demonstrate the 3D printing of a PLA/PHA blend as a potential candidate for biocompatible material applications. The filament for 3D printing consisted of PHA, which contains predominantly 3-hydroxybutyrate units and a small amount of 3

The anionic polymerization of (R)-β-butyrolactone initiated with either 18-crown-6 complexes of a potassium alkoxide or a simple carboxylate (reference initiator) proceeded with inversion of configuration. As a result (R)-β-butyrolactone formed an isotactic poly((S)-β-hydroxybutyrate) with these initiators at room temperature. Polymerization of (R,S)-β-butyrolactone under the same conditions gave an atactic polymer, but at lower temperatures the predominantly syndiotactic form of poly((R,S)-β-hydroxybutyrate) was produced from the racemic monomer.

Novel model block copolymers of (R,S)-β-butyrolactone with pivalolactone (PVL) are prepared in order to define the effect of crystalline domains provided by poly(pivalolactone) on the biodegradability of atactic poly(β-butyrolactone), a-PHB. The “living” a-PHB is synthesized from racemic β-butyrolactone, in the presence of potassium alkoxide/18-crown-6 complex, and such a living polymer is applied for polymerization of PVL, yielding block copolymers, a-PHB-b-PPVL, of tailored molecular weight and composition. The copolymers contain an amorphous phase with T g = 5 °C, associated with the a-PHB block, and a high melting crystalline phase, whose amount increases with PPVL content. Films of copolymers containing 9 (PVL9), 17 (PVL17), and 23 mol % of PPVL (PVL23) are exposed to PHB-depolymerase A from Pseudomonas lemoignei (37 °C, Tris−HCl buffer pH = 8). While plain a-PHB does not biodegrade, the biodegradation rate of a-PHB-b-PPVL copolymers increases (PVL9 ≪ PVL17 < PVL23) along with the increase of crystalline PPVL domains. The biodegradation rate of PVL23 is similar to that of natural (crystalline) PHB. On the basis of a comparison of a-PHB-b-PPVL composition changes (by 1H NMR) with weight loss during biodegradation experiments, it is concluded that in the copolymers studied only the a-PHB block is attacked by the enzyme and that the crystalline block of nonbiodegradable PPVL efficiently promotes enzymatic attack to a-PHB, by providing a binding support to the enzyme.

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