Thermally reversible physical gels of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate]: Part 1 gelation in dimethylformamide

A series of thermally reversible gels made from a solution of bio-based, biodegradable poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHx) in dimethylformamide (DMF) were analyzed using wide angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). WAXD results demonstrate the existence of crystalline PHBHx in the polymer gel by the presence of diffraction peaks characteristic of the α crystalline form. The results obtained from FTIR are consistent with the WAXD, all indicating that gelation is caused by the presence of polymer crystals within the gel system. SEM images confirmed the phase separation of the solvent and the polymer by revealing a highly interconnected, submicron-scale polymer network comprised of PHBHx ribbons and fibrils.