Biodegradable blends based on polyhydroxybutyrate: structure and water diffusion

The present article focuses on the study of novel blends based on poly(3-hydroxybutyrate) (PHB) and polymers with different hydrophilicity (PELD, PA and PVA). Polymer blends were produced from five ratios of PHB/PELD in an effort to regulate the resistance to hydrolysis or (bio)degradation through the control of water permeability. The relation between the water transport and morphology (TEM data) shows the impact of polymer component ratio on the regulation of water flux in hydrophobic matrix. To elucidate the role of hydrophilicity of second component presenting in the PHB blends, we studied the PHB/PA blends where PA is the polyamide resin composed of statistical copolymer of hexamethyleneadipinate and -caprolactam in ratio 1 : 1. The complex of techniques including DCS and FTIR-imaging (for T-scale) demonstrates the interaction between PHB and PA in the temperature ranges of crystallization and melting. The general approach based on Flory- Huggins equation is presented as the way to choose the pairs of compatible or partly compatible polymers. Mechanical characteristics and water permeability of films on the basis of PVAPHB mixtures depending on their composition were investigated. It was shown that the additive of PHB increments water permeability of a polymeric matrix, but at major dosage of PHB the permeability of films can be reduced because of ability of PHB to fix water. It was determined by DSC, polarization IR-spectroscopy, WAXS and SAXS-experiments that there is a connection between structural architecture of films at crystalline (or at molecular) level with water permeability and mechanical performances. It was shown that the decreasing of strength of films occurs at PHB concentration more than 20 % (for PVA-PHB mixtures). Blending PHB with PA and PVA could be a simple and effective method to design new matrices for drug delivery in medicine, while the same procedure applied for PHB-PELD system with better resistance to hydrolysis and lower price than initial PHB could be used as novel bioerodible packaging materials.