Tuning the crystalline and mesophase structure of olefin block copolymer through self-nucleation and annealing treatments.
Tuning the crystalline and mesophase structure of olefin block copolymer through self-nucleation and annealing treatments.
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DOI：
10.1039/c5cp00548e
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发表时间：
2015-06
期刊：
影响因子：
--
通讯作者：
J. Fan;Qinglong Zhang;Jiachun Feng
中科院分区：
文献类型：
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作者：
J. Fan;Qinglong Zhang;Jiachun Feng
作为一种新型的半晶嵌段共聚物，烯烃嵌段共聚物(OBC)的最终性能很大程度上取决于其结晶结构和相分离结构。在本工作中，我们系统地研究了自成核和退火对OBC的片层和中间相分离结构的影响。根据自形核和退火处理后的结晶和熔化行为，可以识别出四个不同的区域，自晶化温度ts在125~109℃之间变化。在区域A中，只有自形核发生，而在区域B中，它与片层增厚共存。在区域C中，只有片层增厚行为。观察到的非连续片层晶体引起的片层增厚表明，紧挨着软块并被困在晶相和非晶相之间的硬块重新排列成相邻的片层晶体应该是OBC片层增厚的机制。令人惊讶的是，在D区，在较低的温度下没有出现片层增厚，并出现了新的小熔融峰。考虑到OBC的嵌段分散性，较低温度下出现的小熔融峰可以归因于结晶能力相对较弱的乙烯序列的结晶，这些乙烯序列不能在标准结晶状态下结晶。基于这些发现，我们对OBCs的片层增厚行为有了一些新的认识，并建立了自成核和退火过程作为调节OBCs晶体结构和相分离结构的有力工具。
As a type of novel semi-crystalline block copolymers, the final properties of olefin block copolymers (OBCs) greatly depend on the crystalline and phase-separated structures. In the present work, we systematically investigated the influence of self-nucleation and annealing on the lamellar and mesophase-separated structure of OBCs. According to the crystalline and melting behavior after self-nucleation and annealing treatments, four different regimes can be recognized with the self-seeding temperature Ts varying from 125 to 109 °C. In regime A, only self-nucleation occurs, while it coexists with lamellar thickening in regime B. In regime C, there is only lamellar thickening behavior. The lamellar thickening induced inconsecutive lamellar crystals observed revealed that the rearrangement of the hard blocks, which are next to the soft blocks and trapped in the intermediate regime between crystalline and amorphous phases, into neighboring lamellar crystals should be the mechanism for the lamellar thickening of the OBCs. Surprisingly, no lamellar thickening occurs and a new small melting peak appears at lower temperatures in regime D. Considering the block dispersity of OBCs, the emergence of a small melting peak at lower temperatures can be attributed to the crystallization of the ethylene sequence with relatively weaker crystallization abilities, which are not able to crystallize in a standard crystalline state. Based on these findings, we gained some new understandings on lamellar thickening behavior of OBCs and established the self-nucleation and annealing process as a powerful tool for tuning the crystalline and phase-separated structures of OBCs.