Experimental Test of Tammann's Nuclei Development Approach in Crystallization of Macromolecules
Experimental Test of Tammann's Nuclei Development Approach in Crystallization of Macromolecules
复制标题
DOI：
10.3139/217.3246
复制
发表时间：
2016-11
影响因子：
1.3
通讯作者：
E. Zhuravlev;J. Schmelzer;R. Androsch;C. Schick
中科院分区：
文献类型：
--
作者：
E. Zhuravlev;J. Schmelzer;R. Androsch;C. Schick
摘要预测可结晶聚合物的超分子结构和性质需要深入了解结晶行为，特别是成核动力学的温度依赖性。通常，在熔体的低过冷度下，通常通过光学显微镜通过分析球晶超结构的演变来评估成核速率/核密度。如果核密度太高，或者如果由于链移动性限制，核形成之后没有生长，则这种方法失败。在这种情况下，可以应用Tammann的两阶段晶核开发方法。它包括在熔体高度过冷时晶核的形成，以及在它们生长成晶体后在更高温度下的检测。虽然最初开发用于分析低分子量化合物，但该方法最近也成功地用于分析聚合物的成核行为，这在本文中以聚（L-乳酸）（PLLA）和聚（ε-己内酯）（PCL）为例进行了证明。而在PLLA的情况下，获得有关等温和非等温成核的信息的能力进行了解释，在PCL的情况下，提出了有关核的热稳定性的新信息。这种分析的重要性，在理解的背景下，在加工相关的冷却条件下的聚合物的结构形成的讨论。
Abstract Prediction of the supermolecular structure and with that of properties of crystallizable polymers requires in-depth knowledge about the crystallization behavior, in particular the temperature-dependence of the nucleation kinetics. Typically, at low supercooling of the melt the nucleation rate/nuclei density often is assessed by optical microscopy, through an analysis of the evolution of the spherulitic superstructure. This approach fails if the nuclei density is too high, or if nuclei formation is not followed by growth due to chain-mobility constraints. In such cases, Tammann's two-stage crystal nuclei development method can be applied. It includes the formation of crystal nuclei at high supercooling of the melt, and their detection at higher temperature, after their growth to crystals. Though initially developed for analysis of low molecular mass compounds, this approach has recently also successfully been employed for analysis of the nucleation behavior of polymers, which is demonstrated here on the examples of poly (L-lactic acid) (PLLA), and poly (∊-caprolactone) (PCL). While in case of PLLA the ability to gain information about isothermal and non-isothermal nucleation is explained, in case of PCL new information about the thermal stability of nuclei is presented. The importance of such analyses in the context of understanding structure formation of polymers at processing-relevant cooling conditions is discussed.