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Formation of well-organized, concentric-ringed spherulites of four-arm star symmetric PEO-b-PCL via confined evaporative crystallization
CrystEngComm ( IF 2.6 ) Pub Date : 2020-09-14 , DOI: 10.1039/d0ce01183e Jing Wei 1, 2, 3, 4, 5 , Lin Wu 6, 7, 8, 9, 10 , Hao Zhu 1, 2, 3, 4, 5 , Yiguo Li 1, 2, 3, 4, 5 , Zongbao Wang 1, 2, 3, 4, 5
CrystEngComm ( IF 2.6 ) Pub Date : 2020-09-14 , DOI: 10.1039/d0ce01183e Jing Wei 1, 2, 3, 4, 5 , Lin Wu 6, 7, 8, 9, 10 , Hao Zhu 1, 2, 3, 4, 5 , Yiguo Li 1, 2, 3, 4, 5 , Zongbao Wang 1, 2, 3, 4, 5
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Formation of well-organized, periodic spherulites of four-arm star symmetric poly(ε-caprolactone)-b-poly(ethylene oxide) (PEO-b-PCL) via confined slow evaporative crystallization of solution-cast films is reported, and the microstructures were characterized by optical microscopy, atomic force microscopy, and X-ray scattering and diffraction techniques. Having a Maltese cross pattern, the spherulites exhibit a unique concentric-ringed morphology under both polarized and unpolarized lights. The pattern regularity and ring periodicity are both controllable. The tunable periodicity is in the range of 10–45 μm, and the size of the spherulites even exceeds one millimeter. It shows that such birefringent concentric-structure is a reflection of periodic change of thickness caused by rhythmic stacking of lamellar crystals with varied orientation along the radial direction. The lamellae in valley bands are nearly flat-on, while the lamellar orientation becomes gradually inclined with normal thickening, leading to continuously enhanced birefringence in ridges. Finally, a coupling of the poor solubility of the PEO block and its inner geometry in the star topology is then presented to illustrate a possible solvent-assisted topology confined mechanism for inducing PCL-dominated rhythmic crystallization into concentric-ringed spherulites.
中文翻译：
通过有限的蒸发结晶形成四臂星形对称PEO-b-PCL的组织良好，同心环状的球晶
-组织良好的，周期性的四臂星形对称聚球晶（ε -己内酯）的形成b（PEO- -聚（环氧乙烷）b -PCL）经由报道了溶液流延膜的有限的缓慢蒸发结晶，并通过光学显微镜，原子力显微镜，X射线散射和衍射技术对微结构进行了表征。具有马耳他十字形图案，在偏振光和非偏振光下，球晶均具有独特的同心环形态。模式规律性和振铃周期都是可控的。可调周期在10–45μm的范围内，球晶的尺寸甚至超过1毫米。结果表明，这种双折射同心结构反映出厚度的周期性变化，这种厚度变化是由沿径向方向变化的层状晶体的节律性堆叠引起的。山谷带中的薄片几乎是平坦的，而层状取向随着正常增厚而逐渐倾斜，导致脊中的双折射不断增强。最后，然后介绍了PEO嵌段的不良溶解性及其在星形拓扑中的内部几何形状的耦合，以说明可能的溶剂辅助拓扑受限机制，用于将PCL主导的节律结晶诱导成同心环状球晶。
更新日期：2020-10-07
中文翻译：
通过有限的蒸发结晶形成四臂星形对称PEO-b-PCL的组织良好，同心环状的球晶
-组织良好的，周期性的四臂星形对称聚球晶（ε -己内酯）的形成b（PEO- -聚（环氧乙烷）b -PCL）经由报道了溶液流延膜的有限的缓慢蒸发结晶，并通过光学显微镜，原子力显微镜，X射线散射和衍射技术对微结构进行了表征。具有马耳他十字形图案，在偏振光和非偏振光下，球晶均具有独特的同心环形态。模式规律性和振铃周期都是可控的。可调周期在10–45μm的范围内，球晶的尺寸甚至超过1毫米。结果表明，这种双折射同心结构反映出厚度的周期性变化，这种厚度变化是由沿径向方向变化的层状晶体的节律性堆叠引起的。山谷带中的薄片几乎是平坦的，而层状取向随着正常增厚而逐渐倾斜，导致脊中的双折射不断增强。最后，然后介绍了PEO嵌段的不良溶解性及其在星形拓扑中的内部几何形状的耦合，以说明可能的溶剂辅助拓扑受限机制，用于将PCL主导的节律结晶诱导成同心环状球晶。
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