二元高分子薄膜在平行電場下的相分離; Phase separation of um-thickness films of a binary polymer melt under in-plane electric fields

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题名:	二元高分子薄膜在平行電場下的相分離;Phase separation of um-thickness films of a binary polymer melt under in-plane electric fields
作者:	王正宏;Chen-Hung Wang
贡献者:	物理研究所
关键词:	相分離;高分子聚合物;去濕潤性;旋轉塗佈;phase separation;phase trnsition;PS;PMMA;order;disorder;polymer;electric field;thin film;blend;dewetting;wetting;temperature control;hole;morphology;spin;casting
日期:	2006-01-12
上传时间:	2009-09-22 10:56:48 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	我們將PS 與PMMA 混合而成的薄膜放在平行薄膜的電場中來研究外場下的相分離(phase separation)。在實驗中發現，相分離會伴隨去潤濕性(dewetting)。在較弱的外場下，去潤濕的過程在相分離的後期會造成洞(dewetting hole)的形成。而在強電場下，這個過程會被抑制。跟早期只有單一組成的薄膜實驗來比，經由相分離形成的洞，其成長速率在洞剛形成的初期是相符的，但是在後期是不同的。藉由光學顯微鏡及原子力顯微鏡(AFM)對相分離中的薄膜表面來做考察，我們給出了在不同電場下上述過程的動力學解釋。在強電場下，電場會破壞相異成分界面的穩定性(interface instability)，從而使界面斷開，形成較小的不互連的相分離結構。我們認為在不同電場下，所呈現的不同的相分離過程，主要是由於，去潤濕性的不穩定性(instability of dewetting)及電場導致的界面不穩定性的競爭造成的。在這個實驗中，我們量測了洞的成長率，相分離結構大小隨時間及電場的變化，以期和單純的相分離及去潤濕性的實驗來比較。 Polymer blends of PS and PMMA are used to study the time evolution of um-thickness film phase separation of binary fluid mixtures under applied in-plane electric fields. It is found that the phase separation is accompanied by dewetting processes (PS dewet PMMA) at the later stage for weak fields, but the dewetting is suppressed while the electric field is increased. The growth rates of holes for binary um-thickness films agree with the classical thin-film system at the early stage but distinct at the late stage. From the profiles of the dewetting domains and optical images of dewetting processes, we provide a dynamical picture of this dewetting process in this thesis. We also find that the electric field will break the spinodal decomposition structures during phase separation so domains become small, with the dewetting holes disappearing under strong fields. The competition between two instabilities induced by the dewetting and electric field makes the phase separation morphology different at weak and strong fields. The power laws of the growth rates of dewetting holes and domain sizes in final states are measured to compare with the normal phase separation and classical dewetting.
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