Further Evidence of Crystallinity-Induced Biodegradation of Synthetic Atactic Poly(3-hydroxybutyrate) by PHB-Depolymerase A from Pseudomonas lemoignei. Blends of Atactic Poly(3-hydroxybutyrate) with Crystalline Polyesters

Abstract

Blends of atactic poly[(R,S)-3-hydroxybutyrate], a-PHB, with poly(ε-caprolactone), PCL, and with poly(l-lactic acid), PLLA, were obtained in the form of compression-molded films. The phase behavior of the blends was different: a-PHB and PCL were totally immiscible, whereas a-PHB/PLLA blends were miscible over the whole composition range. Biodegradation experiments were carried out on the blends and on the plain polymers in a buffered solution of PHB-depolymerase A from Pseudomonas lemoignei (Tris−HCl, pH = 8, T = 37 °C). None of the pure blend components (a-PHB, PCL, PLLA) showed any weight loss upon enzyme exposure. Conversely, both a-PHB/PCL and a-PHB/PLLA blends biodegraded. Analysis of the biodegradation products and of blend composition changes during biodegradation demonstrated that in both blends only the a-PHB component undergoes enzymatic hydrolysis. The results support the hypothesis that the crystalline polyester blended with a-PHB promotes a-PHB enzymatic hydrolysis by providing stable binding sites to the enzyme. The dependence of biodegradation rate on blend composition is different in (immiscible) a-PHB/PCL and (miscible) a-PHB/PLLA blends and can be explained in terms of different phase behavior and morphology.

Effect of biopolymer blends on physical and Acoustical properties of biocomposite foams

“…Majority of the studies on PLA-PHA blends used solvent casting to prepare the materials [16][17][18][19] and found the two polymers immiscible except for very low molecular weight PLA 18 or PHB. 19 Richards et al 20 investigated the thermal properties and morphology of foams manufactured from blends of PLA and PHBV with CO 2 as the blowing agent and showed that PLA and PHBV are immiscible and blending achieves only a physical dispersion of one component into the other.…”

Crystal Growth in Poly(L‐lactide) Thin Film Revealed by in situ Atomic Force Microscopy

“…On the contrary, in the case of PLLA film, optical microscopic investigations revealed that PLLA spherulites have no extinction bands, suggesting that lamellar crystals are not periodically twisted. [13,14] Atomic force microscopy (AFM) is now widely accepted as a useful method to characterize polymeric materials, and to investigate the surface of the material. During polymer crystallization, crystalline lamellae develop in the molten amorphous matrix.…”

Forensic Engineering of Advanced Polymeric Materials. Part 1 – Degradation Studies of Polylactide Blends with Atactic Poly[(R,S)-3-hydroxybutyrate] in Paraffin

“…Various attempts have been made to blend PLA or PHB with synthetic or natural polymers and to determine the influence of the components on the properties and biodegradability of the resulting material. [36][37][38][39][40][41] Blends of poly(L-lactide) (PLLA) with natural or synthetic PHB were miscible, or semi-miscible depending on composition, when one compound possessed a low molar mass, and were immiscible with high-molar mass compounds, e.g. PLLA, natural or synthetic PHB and PHBV.…”

“…PLLA, natural or synthetic PHB and PHBV. 37,[42][43][44][45][46] The degradation rate and mechanical properties are key factors in many applications, especially in packaging materials for long shelf life applications, of degradable polymers. 47 Recently, we originally demonstrated that the degradation of PLA films occurs in paraffin because of the residual water content.…”