Vertical phase separation and liquid-liquid dewetting of thin PS/PCL blend films during spin coating.
Vertical phase separation and liquid-liquid dewetting of thin PS/PCL blend films during spin coating.
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DOI：
10.1021/la104003p
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发表时间：
2011-01
期刊：
影响因子：
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通讯作者：
Meng Ma;Zhoukun He;Jinghui Yang;Qi Wang;Feng Chen;Ke Wang;Qin Zhang;H. Deng;Q. Fu
中科院分区：
文献类型：
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作者：
Meng Ma;Zhoukun He;Jinghui Yang;Qi Wang;Feng Chen;Ke Wang;Qin Zhang;H. Deng;Q. Fu
采用旋涂法制备了无定形聚合物聚苯乙烯（PS）和结晶聚合物聚己内酯（PCL）的共混物薄膜。用X射线光电子能谱（XPS）测定了共混膜的表面化学组成，用原子力显微镜（AFM）观察了共混膜的表面和界面形貌变化。通过改变PS浓度并将溶液的PCL浓度保持在1wt%，构建了各种各样的形态。结果表明，随着PS浓度的增加，共混膜的形态可分为三个区域。在区域I中，当PS浓度低于0.3wt%时，PS岛域嵌入PCL晶体中，并且PS岛的尺寸随着PS浓度的增加而增加。在区域II中，当PS的浓度在0.35和0.5wt%之间时，获得由低边缘包围的具有不同尺寸的孔。在选择性清洗PS结构域后，我们研究了PS/PCL的界面形态，发现上层的PS富集层延伸到底层的PCL层，形成了围绕孔的沟槽。当PS浓度大于0.5wt%时，共混膜呈现出富PS层和富PCL晶体层的双层结构。最后，不同的表面和界面形态的形成机制进行了进一步讨论，在垂直相分离的层状结构，然后在旋涂过程中的液-液脱湿和结晶过程。
Thin films of an amorphous polymer, polystyrene (PS), and a crystalline polymer, poly(ε-caprolactone) (PCL), blend were prepared by spin coating a toluene solution. Surface chemical compositions of the blend films were measured by X-ray photoelectron spectroscopy (XPS), and the surface and interface topographical changes were followed by atomic force microscopy (AFM). By changing the PS concentration and keeping the PCL concentration of the solution at 1 wt %, a great variety of morphologies were constructed. The results show that the morphology of the blend films can be divided into three regions with increasing PS concentration. In region I, PS island domains are embedded in PCL crystals when the PS concentration is lower than 0.3 wt % and the size of the PS island increases with increasing PS concentration. In region II, holes with different sizes surrounded by a low rim are obtained when the concentration of PS is between 0.35 and 0.5 wt %. After selectively washing the PS domains, we studied the interface morphology of PS/PCL and found that the upper PS-rich layer extended into the bottom PCL layer, forming a trench surrounding the holes. In region III, an enriched two-layer structure with the PS-rich layer on top of the blend films and the PCL-rich crystal layer underneath is obtained when the concentration of PS is higher than 0.5 wt %. Last, the formation mechanism of the different surface and interface morphologies is further discussed in terms of the vertical phase separation to a layered structure, followed by liquid-liquid dewetting and crystallization processes during spin coating.