Role of bacterial cellulose and poly (3-hydroxyhexanoate-co-3-hydroxyoctanoate) in poly (3-hydroxybutyrate) blends and composites

Biodegradable and biocompatible poly (3-hydroxybutyrate) (PHB) is considered a good candidate for biomedical applications provided that its inherent brittleness and thermal stability are corrected. In this work, poly (3-hydroxyhexanoate-co-3-hydroxyoctanoate) (PHHO) and bacterial cellulose nanofibers (BC) were used as “soft” and “stiff” modifiers to improve PHB properties. PHHO (5–20 wt%) increased the thermal stability of PHB and PHB-BC composites. On the other hand, BC increased the glass transition and the crystallization temperature of PHB in the blends. The surface morphology of PHB was differently changed by the addition of PHHO and BC: a microporous surface morphology with many well spread pores was produced by the addition of PHHO (20–50 wt%) and a smoother surface by the addition of BC. Still, the surface morphology of PHB/PHHO blends, with homogenously spread submicronic pores, was not changed by BC. Thermal, structural and morphological investigations showed that BC nanofibers are mainly located in PHHO rich phase and at interface. PHB nanocomposite with 20 wt% PHHO showed balanced stiffness-toughness properties and excellent thermal stability, with the onset thermal degradation temperature higher than 270 °C. These properties and its porous surface morphology besides the inherent biodegradability and biocompatibility promote this nanocomposite as a valuable material for tissue engineering. It is remarkable that these favorable properties were obtained by a simple, easily controlled method without additional processes or additives.