Controlling Polymer Crystallization Kinetics by Sample History
Controlling Polymer Crystallization Kinetics by Sample History
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DOI：
10.1002/macp.201700315
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发表时间：
2018-02-01
影响因子：
2.5
通讯作者：
Reiter, Guenter
中科院分区：
文献类型：
--
作者：
Poudel, Purushottam;Chandran, Sivasurender;Reiter, Guenter
在本文中，系统的变化，等温结晶动力学（在Tc = 200摄氏度）的非平衡的全同立构聚苯乙烯薄膜，通过旋涂产生的报告。通过在T-a = 250 ℃下退火膜来调整动力学，即，高于其标称熔融温度（Tm（DSC）= 220 ℃）。通过增加在T-a处平衡所需的时间（t（a）），观察到生长速率呈指数下降，晶体成核密度显著下降约三个数量级。特征指数衰减时间比在T-a时的平衡蠕动时间长大约四个数量级。有趣的是，随着t（a）的增加，观察到片状晶体的形态从球晶到高度相当均匀的六边形，最后到高度呈现周期性调制的六边形的变化。这些观察结果表明，理解和调整的结晶动力学的聚合物薄膜在静态条件下需要的知识如何强烈链构象偏离平衡。
In this paper systematic changes in the isothermal crystallization kinetics (at T-c = 200 degrees C) of nonequilibrated isotactic polystyrene films, generated through spin coating are reported. Kinetics is tuned by annealing films at T-a = 250 degrees C, i.e., above their nominal melting temperature (T-m(DSC) = 220 degrees C). An exponential decrease in growth rate and a significant decrease of crystal nucleation density by approximately three orders of magnitude are observed by increasing the time (t(a)) provided for equilibration at T-a. The characteristic exponential decay time is approximately four orders of magnitude longer than the equilibrium reptation time at T-a. Interestingly, with increasing t(a), a change in the morphology of lamellar crystals varying from spherulites to hexagons of rather uniform height to finally hexagons exhibiting periodic modulations in height is observed. These observations reveal that understanding and tuning the crystallization kinetics of polymer films under quiescent conditions requires knowledge on how strongly chain conformations deviate from equilibrium.