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 with 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 and a mesophase. Specific IR bands in s-polarized (electric field vector along the fiber axis) spectra have been identified to arise from the mesophase. For fibers annealed at low stress (1.6 MPa), the mesophase content practically disappears but can be recovered with tensile drawing. In-situ WAXD and polarized ATR-FTIR studies, performed during cyclic tensile loading/unloading, have revealed that the mesophase formation/dissolution is highly reversible in fibers annealed at low stress. This reversibility behavior, and the lack of off-axis reflections in WAXD patterns, support the theory that the mesophase is made of conformationally disordered and stretched chains, which are mainly located in-between α-crystals.

聚（3-羟基丁酸酯）（P3HB）单丝（直径~90 μm）的结构变化，由在拉伸应力下退火（80-130°C 下 1.6-40 MPa 负载 1 小时）引起的，已使用同步加速器广角进行了研究X 射线衍射 (WAXD) 和偏振衰减全反射傅里叶变换红外 (ATR-FTIR) 光谱。熔纺 P3HB 纤维由非晶相、结晶 α 相和中间相组成。s 中的特定红外波段极化（沿纤维轴的电场矢量）光谱已被确定为由中间相产生。对于在低应力 (1.6 MPa) 下退火的纤维，中间相含量实际上消失了，但可以通过拉伸恢复。在循环拉伸加载/卸载期间进行的原位 WAXD 和极化 ATR-FTIR 研究表明，在低应力下退火的纤维中，中间相的形成/溶解是高度可逆的。这种可逆行为，以及 WAXD 模式中缺乏离轴反射，支持中间相由构象无序和拉伸链组成的理论，这些链主要位于 α 晶体之间。