Phase separation and dewetting in polystyrene/poly(vinyl methyl ether) blend thin films in a wide thickness range
Phase separation and dewetting in polystyrene/poly(vinyl methyl ether) blend thin films in a wide thickness range
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DOI：
10.1016/j.polymer.2007.11.031
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发表时间：
2008-01
期刊：
影响因子：
4.6
通讯作者：
H. Ogawa;T. Kanaya;K. Nishida;G. Matsuba
中科院分区：
文献类型：
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作者：
H. Ogawa;T. Kanaya;K. Nishida;G. Matsuba
用光学显微镜（OM）、原子力显微镜（AFM）和小角光散射（LS）研究了聚苯乙烯（PS）和聚乙烯基甲基醚（PVME）共混物薄膜在65μm ~ 42 nm（Rg = 2.5Rg，Rg为聚合物的回转半径）两相区的相分离和去湿过程。结果发现，相分离和去湿过程依赖于膜的厚度，并分为四个厚度区域。在15μm以上的第一个区域，以类似于体相的方式发生失稳分解（SD）型相分离，并且没有观察到去湿。该区域可被视为块体。在15 ~ 11 μm的第二区域，SD型相分离在早期进行，而SD的特征波长随膜厚的增加而减小。在后期阶段，由相分离引起去湿。在101 μm ~ 10200 nm之间的第三个区域，即使在早期阶段也观察到去湿。脱湿形态非常不规则，没有观察到明确的特征波长。可以预期，不规则的形态是由相分离和去湿的特征波长混合引起的。在第四个区域低于200 nm的去湿后，长时间的孵化时间与特征波长，这与膜厚度减小。分析认为，在孕育期内，薄膜中形成了层状结构，并通过毛细波动机制或成分波动机制触发去湿。
Phase separation and dewetting processes of blend thin films of polystyrene (PS) and poly(vinyl methyl ether) (PVME) in two phase region have been studied in a wide film thickness range from 65μm to 42nm (∼2.5Rg, Rgbeing radius of gyration of a polymer) using optical microscope (OM), atomic force microscope (AFM) and small-angle light scattering (LS). It was found that both phase separation and dewetting processes depend on the film thickness and were classified into four thickness regions. In the first region above ∼15μm the spinodal decomposition (SD) type phase separation occurs in a similar manner to bulk and no dewetting is observed. This region can be regarded as bulk. In the second region between ∼15 and ∼1μm, the SD type phase separation proceeds in the early stage while the characteristic wavelength of the SD decreases with the film thickness. In the late stage dewetting is induced by the phase separation. In the third region between ∼1μm and ∼200nm the dewetting is observed even in the early stage. The dewetting morphology is very irregular and no definite characteristic wavelength is observed. It is expected that the irregular morphology is induced by mixing up the characteristic wavelengths of the phase separation and the dewetting. In the fourth region below ∼200nm the dewetting occurs after a long incubation time with a characteristic wavelength, which decreases with the film thickness. It is considered that the layered structure is formed in the thin film during the incubation period and triggers the dewetting through the capillary fluctuation mechanism or the composition fluctuation one.