Novel amphiphilic poly(ester-urethane)s based on poly[(R)-3-hydroxyalkanoate]: Synthesis, biocompatibility and aggregation in aqueous solution

Background: The aim of this work was to develop polyhydroxyalkanoates (PHAs) for blood contact applications, and to study their self-assembly behavior in aqueous solution when the PHAs are incorporated with hydrophilic segments. To do this, poly(ester-urethane) (PU) multiblock copolymers were prepared from hydroxyl-terminated poly(ethylene glycol) (PEG) and hydroxylated poly[(R)-3-hydroxyalkanoate] (PHA-diol) using 1,6-hexamethylene diisocyanate as a coupling reagent. The PEG segment functions as a soft, hydrophilic and crystalline portion and the poly[(R)-3-hydroxybutyrate] segment behaves as a hard, hydrophobic and crystalline portion. In another series of PU multiblock copolymers, crystalline PEG and completely amorphous poly[((R)-3-hydroxybutyrate)-co-(4-hydroxybutyrate)] behaved as hydrophobic and hydrophilic segments, respectively. Results: The formation of a PU series of block copolymers was confirmed by NMR, gel permeation chromatography and infrared analyses. The thermal properties showed enhanced thermal stability with semi-crystalline morphology via incorporation of PEG. Interestingly, the changes of the hydrophilic/hydrophobic ratio led to different formations in oil-in-water emulsion and surface patterning behavior when cast into films. Blood compatibility was also increased with increasing PEG content compared with PHA-only polymers. Conclusion: For the first time, PHA-based PU block copolymers have been investigated in terms of their blood compatibility and aggregation behavior in aqueous solution. Novel amphiphilic materials with good biocompatibility for possible blood contact applications with hydrogel properties were obtained.