本研究在探討雙團鏈高分子PS-b-P4VP薄膜旋鍍在矽基材SiOx/Si以及透過表面改質的聚苯乙烯毛刷基材PS-SiOx/Si，利用THF溶劑蒸氣退火刺激後，其除潤現象、奈微米結構對於薄膜不穩定性間的相依關係。首先PS-b-P4VP團鏈共聚高分子在基材效應的實驗中，在親水性的矽基材上，由於極性基材易吸附P4VP鏈段，造成在退火過程中，該鏈段受到基材錨定作用而形成潤濕層，部分微胞移動受限於錨定影響，聚變過程發生緩慢，薄膜穩定度高。相對於極性基材，對於接有毛刷層的改質基板上，此毛刷層扮演著阻隔層的角色，隔絕極性基材對於P4VP鏈段間的吸引力。在溶劑蒸氣退火下，微胞聚變過程中所釋出的間隙將會在薄膜上造成孔洞，孔洞形成造成薄膜上洞與鄰近地區薄膜以及大小洞間有壓力差存在，使得薄膜上為趨於表面能最小，洞與洞間的彼此融合或增長驅使薄膜推擠而形成梯田式堆疊，同時微胞上PS與接枝層PS同種鏈段間自除潤發生，驅使液滴形貌的形成。結合影像定量分析統整出對於薄膜上的孔洞覆蓋率變化之趨勢，階段性地呈現薄膜除潤行為的演化過程。最後探討在溶劑退火過程中，對稱型PS22k-b-P4VP22k及非對稱型PS19k-b-P4VP22k之PS鏈段分子量不同反映出迥然不同的表徵。將利用混?不同分子量的PS均聚物修飾鏈長差異及提升毛刷層接枝密度以改善薄膜不穩定性之現象。
In this study, I investigate PS-b-P4VP thin films spin-coated on bare (SiOx/Si) and PS-grafted(PS-SiOx/Si) silicon substrates and observe the relationship between film instability and internal nanostructures during solvent annealing in THF solvent vapor. The first experiment is to study the substrate effect. The hydrophilic of bare silicon substrates preferentially adsorbs P4VP segments in the annealing process, causing block copolymer chains to form a wetting layer at the substrate interface. At early stages, micellar movement is restricted by the anchoring effect, which induced slow fusion process. Hence, the film did not rupture. Compared to micellar films on polar substrates, fusion of PS-b-P4VP micelles on the PS-grafted substrate occurs quickly upon solvent annealing. This is because the PS-grafted brush layer obstructs the attractive interaction between SiOx/Si and P4VP chains. Furthermore, micellar fusion leads to micro-sized holes in the film. Because of the formation of holes, there exists pressure difference(Laplace pressure)between holes and their surrounding areas. In order to reduce the surface free energy, the holes grew by merging with their neighboring analog. At intermediate stages of solvent annealing, terraced structures start to form whereas at final stages droplets form. The driving force for film instability on PS-SiOx/Si is the auto phobic behavior between PS segments within micelles and the PS-grafted substrate. In addition, we find different molecular weights of PS segments between symmetric and asymmetric PS-b-P4VP induced different surface characterizations upon solvent annealing. Dewetting behavior of asymmetric PS-b-P4VP thin films is more serious than that of symmetric PS-b-P4VP ones. The last section, I attempt to improve the film instability of PS-b-P4VP by blending PS homopolymers of various molar masses.
