Preparation and selected properties of organic/inorganic composites based on poly(ester-ether-ester) terpolymers and nanocrystalline hydroxyapatite

Novel organic/inorganic hybrid materials prepared from multiblock terpolymer as a polymeric matrix containing phthalic acid segments (as in poly(butylene terephthalate) (PBT) as hard block and hydrogenerated dimmer fatty acid, namely dilinoleic acid sequences (DLA) as hydrophobic soft block, and poly(ethylene glycol) (PEG) as second soft block of hydrophilic nature are presented in this work. Two types of nanocrystalline hydroxyapatites (non-calcined, HAP I, and sintered, HAP III) were used in amount of 0.5 wt% as inorganic phase within hydrophilic/hydrophobic multiblock terpolymer matrix. These hybrid materials were prepared during in situ polycondensation method. Alpha-tocopherol was used as non-toxic thermal stabilizer since these materials are targeted for biomedical applications. Additionally, the possibility of stabilizing effect of HAPs was evaluated through the synthesis of nanocomposites without alpha-tocopherol (only in the presence of HAP). It has been found that naocrystalline hydroxyapatite can serve as a very effective stabilizing agent in term of the enhancement of mechanical properties of poly(ester-ether-ester) terpolymers containing PEG. Thermal and mechanical properties of organic/inorganic composite (hybrid) materials were strongly dependent on the type of HAP: higher tensile stress and strain, and increased glass transition temperature were found for composites containing sintered HAP III.