Reversible mesophase in stress-annealed poly(3-hydroxybutyrate) fibers: A synchrotron x-ray and polarized ATR-FTIR study

Structural changes in poly(3-hydroxybutyrate) (P3HB) monofilaments (diameter ~90 μm), induced by annealing under tensile stress (1 h with 1.6–40 MPa loading at 80–130 °C) have been investigated synchrotron wide-angle x-ray diffraction (WAXD) and polarized attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Melt-spun P3HB fibers consist of an amorphous phase, a crystalline α-phase mesophase. Specific IR bands s-polarized (electric field vector along the fiber axis) spectra identified to arise from For annealed low (1.6 MPa), mesophase content practically disappears but can be recovered drawing. In-situ WAXD ATR-FTIR studies, performed during cyclic loading/unloading, revealed that formation/dissolution is highly reversible stress. This reversibility behavior, lack off-axis reflections patterns, support theory made conformationally disordered stretched chains, which are mainly located in-between α-crystals.