Fractions of Different Mobility in Semicrystalline Polymers Revealed from Temperature Dependent Heat Capacity and NMR Measurements

摘要

Fractions of different molecular mobility of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymers were studied by heat capacity, dielectric and shear Spectroscopy as well as variable temperature solid-state wide-line ~1H NMR and solid-state high-resolution ~(13)C NMR Spectroscopy. Three different fractions were identified and quantified. Following the terminology used in calorimetry these are the crystalline, the rigid amorphous, and the mobile amorphous fraction, respectively. Also the absolute values are different the temperature and the concentration dependencies are the same for all methods. The content of the rigid amorphous fraction decreases with increasing 3-hydroxyvalerate content in PHBV and with increasing temperature. The brittleness of PHB may be partly attributed to the rigidness of the noncrystalline region at room temperature, while the improvement of the properties of PHBV may come from the enhanced mobility of the noncrystalline region.