| 摘要: | 本研究探討PS24k-P4VP9.5k(TOB)0.7於o-xylene溶液之相行為。藉由調控溶液濃度，觀察PS24k-P4VP9.5k(TOB)0.7於溶液中結構之演變。在SAXS圖中，發現低濃度[0.12.5 wt%]PS24k-P4VP9.5k(TOB)0.7溶液為微胞結構，中濃度[5wt%-10wt%]時PS24k-P4VP9.5k(TOB)0.7微胞結構相轉變為單一鏈超分子複合物，高濃度[>10wt%]時，單一鏈超分子複合物因彼此產生糾纏而形成有序結構。由FTIR數據顯示，PS24k-P4VP9.5k(TOB)0.7溶液濃度越高，形成P4VP(TOB)x之比例越高，導致χPS – P4VP值下降，因而使微胞結構崩解形成單一鏈超分子複合物。根據PS24k-P4VP9.5k(TOB)0.7溶液相之結果，發現5wt% PS24k-P4VP9.5k(TOB)0.7溶液為單一鏈之結構，因此有利於自組裝形成奈米有序陣列。使用PS選擇性良溶劑於飽合蒸氣壓下，對5wt% PS24k-P4VP9.5k(TOB)0.7薄膜溶劑退火，發現隨著蒸氣壓的提高，P4VP(TOB)0.7液晶相會形成強垂直錨定效應，進而引導奈米陣列的有序性，因此由實驗結果可得到12x12μm2之長程有序奈米陣列。若將不同濃度PS24k-P4VP9.5k(TOB)0.7薄膜以非選擇性溶劑於非飽和蒸氣壓下溶劑退火，發現液晶相P4VP(TOB)0.7會形成柱狀結構(液晶相column)，因為液晶相column偏好平坦的材料?界面（IMDS），因此主導PS24k-P4VP9.5k(TOB)0.7形成六角柱階層結構。因為液晶相column偏好平坦的IMDS而不易彎曲，當形成缺陷時圓柱易發生斷裂，導致晶粒尺寸變小而形成短程有序奈米陣列。在應用端的部份，我們利用剪應力的方式塗佈高濃度PS24k-P4VP9.5k(TOB)0.7溶液於基材上，搭配高溫熱回火的方式，誘導刮膜形成高度有序奈米陣列。有趣的是，若使用非選擇性溶劑於非飽和蒸氣壓下溶劑退火此高度有序之刮膜，則可得到六方堆積垂直六角柱陣列。
In this study, we have investigated the solution behaviours of PS24k-P4VP9.5k(TOB)0.7 in o-xylene by means of small-angle X-ray scattering. We found three regions of structural evolution depending on polymer concentrations in o-xylene. At low concentrations (0.12.5 mass%) PS24k-P4VP9.5k(TOB)0.7 forms micelles whereas at medium concentrations (510 mass%), single chains comprised of supramolecular PSP4VP/TOB complex are dispersed in o-xylene. By contrast, as PS24k-P4VP9.5k(TOB)0.7 becomes higher than a critical concentration (> 10 mass%), the single chains of supramolecular complex can self-assemble to form an ordered structure. FTIR data demonstrate that TOB molecules exhibit a high tendency to selectively bind with the P4VP block because of hydrogen bonds. As a result, the selective addition of TOB within the P4VP block reduces the χPS – P4VP (the Flory-Huggins interaction between the PS and P4VP) so that the molecular micelles (formed by the aggregation of the whole PS-b-P4VP chain molecules) dissolute to form free single chains comprised of supramolecular PSP4VP/TOB complex. Because the free single chains add flexibility in self-assembly in thin film nano-structures, spin-coating from an o-xylene solution of 5 mass% of PS24k-P4VP9.5k(TOB)0.7 followed by solvent annealing in saturated vapour of a PS-selective solvent can lead to an ordered array of nanodomains in thin films. The reason is that at high vapor pressure, TOB molecules preferentially form homeotropic-oriented nematic phase within the P4VP domain, which improves the long-ranged ordering of self-assembled nanodomains in thin films. By contrast, upon solvent annealing in unsaturated vapour of a non-selective solvent, TOB molecules intend to form a column phase within the P4VP matrix. Since the column phase of TOB causes planar inter-domain interfaces between PS and P4VP blocks, the PS nanocylinders embedded with the P4VP9.5k(TOB)0.7 matrix exhibit a hexagonal shape. Moreover, the formation of the TOB column phase also increases rigidity in the PS cylinders. As a result, any defects, such as dislocations as well as disclinations, may cause high entropic penalty. In order to release this penalty around the effects, the PS nanocylinders tend to rupture, giving rise to polygrains of short PS cylinders within the P4VP/TOB matrix.
For potential applications, we used deposit and scrape wet polymer solutions onto substrates under shearing fields to form thick films. Then isothermal annealing at a high temperature was imposed onto the films to induce highly-oriented arrays of parallel nanocylidrical nanodomains. Interestingly, after the scraped films were subjected to solvent annealing in vapor of a non-selective solvent,we obtained high arrays of hexagonal-packing perpendicularly-oriented hexagonal-shaped cylinders. |
