Dynamically confined crystallization in a soft lamellar space constituted by alternating polymer co-brushes
Dynamically confined crystallization in a soft lamellar space constituted by alternating polymer co-brushes
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DOI：
10.1016/j.polymer.2011.08.004
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发表时间：
2011-09
期刊：
影响因子：
4.6
通讯作者：
N. Xia;Guoliang Zhang;Tao Li;Wei Wang;Hui Zhu;Yongming Chen;Guohua Deng
中科院分区：
文献类型：
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作者：
N. Xia;Guoliang Zhang;Tao Li;Wei Wang;Hui Zhu;Yongming Chen;Guohua Deng
用原位FT-IR和DSC方法研究了PCL和PEO侧链交替连接在聚苯乙烯-马来酰亚胺主链上的聚合物共刷子中PCL侧链的结晶动力学和行为。Avrami分析表明，指数n从10℃时的1增加到30℃时的2，表明PCL侧链通过均相或非均相成核进行受限结晶。PLM的形态表征显示典型的球晶，其大小取决于结晶温度，进一步的AFM可视化显示在30℃时典型的PCL片层和10℃时的破碎片层嵌入到球晶内的PEO+主干基质中。这种片层结构解释了Avrami指数为n-≤+2的受限结晶，断片的形成可以进一步解释Avrami指数在10℃时下降到n-≈-1的原因，即孤立晶体中的均匀形核。基于它们特殊的分子结构，提出了动态受限结晶的概念。与静态受限结晶相比，受限空间的构建和结晶过程几乎是同步的。球晶的形成在介观上揭示了整个分子通过常规结晶聚合物的路径运动和组装的过程，而PCL侧链在由聚苯乙烯-马来酰亚胺的刚性主链和软性PEO层构成的空间中的结晶微观上反映了一些传统嵌段共聚物中观察到的受限特征。
Crystallization kinetics and behavior of PCL side chains in polymer co-brushes constituted with PCL and PEO side chains alternatively attached on poly(styrene-alt-maleimide) backbones have been determined using in-situ FT-IR and DSC methods. Avrami analysis shows the exponent n increasing from one at 10 °C to two at 30 °C, demonstrating confined crystallization of PCL side chains through homogeneous or heterogeneous nucleation. PLM morphological characterization displays typical spherulites of which size is dependent on the crystallization temperature and further AFM visualization shows typical PCL lamellae at 30 °C and broken lamellae at 10 °C embedded within PEO + backbone matrix inside of spherulites. Such lamellar structure explains the confined crystallization with Avrami exponent n ≤ 2. Formation of the broken lamellae can further clarify the reason why Avrami exponent decreases to n ≈ 1 at 10 °C, that is, homogeneous nucleation in the isolated crystals. Dynamically confined crystallization has been proposed based on their special molecular architecture. Comparing to statically confined crystallization, the construction of confined space and the crystallization process were almost synchronous. The formation of spherulites mesoscopically reveals the entire molecule motion and assembly through a pathway of conventional crystalline polymers and the crystallization of PCL side chains in a space constituted by stiff backbones of poly(styrene-alt-maleimide) plus soft PEO layer microscopically reflects a confined character which has been observed in some conventional block copolymers.