Small- and wide-angle X-ray scattering study on α′-to-α transition of Poly(L-lactide acid) crystals
Small- and wide-angle X-ray scattering study on α′-to-α transition of Poly(L-lactide acid) crystals
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DOI：
10.1016/j.polymer.2019.01.088
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发表时间：
2019-03-22
期刊：
影响因子：
4.6
通讯作者：
Zhang, Jianming
中科院分区：
文献类型：
--
作者：
Hu, Jian;Wang, Jiping;Zhang, Jianming
我们用时间分辨同时小角和广角X射线散射(SAXS/WAXS)测量结合温度跳跃(T-JUMP)装置研究了聚L-丙交酸(PLLA)晶体在高温等温退火过程中的α‘到α转变。当在短时间内(约10s)加热到150℃时，观察到在预先存在的α‘晶区内熔化，然后再结晶成相邻的α晶体，表现为不连续的一级α’到α的转变，证实了熔化-再结晶机制与连续的晶体完整性共存。此外，在α‘-α转变过程中，疏松堆积的10/3螺旋的α’-晶体通过扩大横向晶体尺寸而不是片层厚度重新组织成稳定的非晶。基于我们的结构表征，提出了PLLA晶体从α‘到α转变的微观机制，并用动态蒙特卡罗模拟进行了验证。
We employed time-resolved simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) measurements in combination with a temperature-jump (T-jump) installment to investigate alpha'-to-alpha transition in poly(L-lactide acid) (PLLA) crystals during isothermal annealing at a high temperature. Upon heating in a short period (ca. 10s) to the annealing temperature 150 degrees C, the melting within the pre-existing alpha'-crystal domains before recrystallization into neighboring alpha-crystals was observed, appearing as discontinuous first order alpha'-to-alpha transition, which confirms the melting-recrystallization mechanism co-existing with continuous crystal perfection. Furthermore, during alpha'-to-alpha transition the loosely packed 10/3 helices of alpha'-crystals reorganized into the stable acrystals by extending the lateral crystal sizes rather than the lamellar thickness. Based on our structural characterization, the microscopic mechanism of alpha'-to-alpha transition in PLLA crystals was proposed and approved by dynamic Monte Carlo simulations.