IRC in Polymer Science and Technology, School of Physics and Astronomy, University of Leeds, Leeds, UK.
Acta Biomater. 2011 Apr;7(4):1535-41. doi: 10.1016/j.actbio.2010.12.023. Epub 2010 Dec 25.
Highly oriented poly(glycolic acid) (PGA) fibres with an initial tensile strength of 1.1 GPa and different lamellar morphologies were prepared and studied during degradation in aqueous media at 37°C. A combination of small- and wide-angle X-ray scattering was used to study the structural changes during degradation and to generate two structural models of highly oriented PGA fibres with different lamellar morphologies. It is shown that as a result of crystallisation during degradation PGA crystals grow preferentially along the (110) and (020) directions of the crystal lattice or perpendicular to the orientation direction of the fibres. (1)H nuclear magnetic resonance measurements revealed three phases within the fibres with different relaxation times: (1) a mobile amorphous phase with a short relaxation time; (2) a semi-rigid phase with an intermediate relaxation time; (3) a rigid crystalline phase with a longer relaxation time. It is shown that the mobile amorphous phase degrades very rapidly and that it plays only a small role in the tensile mechanical behaviour of the fibres during degradation. It is shown that semi-rigid chains connecting crystalline domains are responsible for transferring the stress between crystalline domains and carrying the tensile deformation. It is proposed that once these tie molecules degrade considerably the oriented fibres very rapidly lose their strength retention.
在 37°C 的水性介质中降解时，制备并研究了具有初始拉伸强度为 1.1 GPa 和不同层状形态的高度取向的聚（乙醇酸）（PGA）纤维。使用小角和广角 X 射线散射的组合来研究降解过程中的结构变化，并为具有不同层状形态的高度取向 PGA 纤维生成两个结构模型。结果表明，由于降解过程中的结晶，PGA 晶体优先沿晶格的（110）和（020）方向或垂直于纤维的取向方向生长。（1）H 核磁共振测量揭示了纤维内具有不同弛豫时间的三个相：（1）具有短弛豫时间的可移动非晶相；（2）具有中间弛豫时间的半刚性相；（3）具有长弛豫时间的刚性结晶相。结果表明，可移动非晶相降解非常迅速，并且在降解过程中对纤维的拉伸力学性能的影响很小。结果表明，连接结晶区的半刚性链负责在结晶区之间传递应力并进行拉伸变形。提出的观点是，一旦这些连接分子降解，定向纤维就会迅速失去强度保持。
