失措型線性ABC三嵌段及ABCBA五嵌段共聚合物自組裝行為的比較

Abstract

本研究運用自洽平均場理論探討熔融態ABCBA線性五嵌段共聚合物在強聚集與失措型之自組裝微結構衍變。首先我們建構了ABCBA線性五嵌段在強聚集(XN=80)的三角相圖以探討組成與不相容參數之間的影響，在強作用力參數下各成分傾向自我聚集，因而多形成核-殼的微結構形態，此外由於ABCBA線性五嵌段共聚合物中A鏈段的兩個自由端可以更為任意填充於各鏈段之間，因而舒緩了形成曲面所造成的packing frustration，因此整張相圖可以看到連續性結構(如：核-殼gyroid、GA/GC、FdddC)佔有為數可觀的區域。而失措型係指A和C兩個Flory-Huggins作用力參數最小，A與C成分傾向接觸的力驅使突破構型的限制產生多樣的微結構，為了深入探討失措型系統的相行為，接著我們選定強聚集特有的相(FdddC/B)將XacN調降，由於相平衡的驅動力從內能轉變為entropic energy，因此隨著XacN下降形態的衍變依序為FdddC/B →GC/B→CC/B，並在相產生最大變化處(XabN=XbcN=80、XacN=20)建立三角相圖，相圖當中發現了針織狀結構(knitting pattern)、穿孔式結構、螺旋狀結構等許多特有的形態。這是由於A與C成分想要接觸時會呈現蜷縮或是反摺(folding)的構型，使得C鏈段從兩邊都被拉長，曲率變化幅度更大，因此比起ABC線性三嵌段共聚合物發現有更為多元的結構。

The phase behavior of ABCBA linear pentablock terpolymer with strong segregation and frustrated interaction is studied by 3-D self-consistent field theory (SCFT). First, the ABCBA triangle phase diagram in strong segregation strength at symmetric interaction parameter is constructed to discuss the influence of compositions and Flory-Huggins parameters. Our results reveal that many core-shell morphology are formed because of strong segregation between each component. Moreover, the two free ends of A blocks in ABCBA pentablock enable the macromolecules to relieve the packing frustration. Therefore, it forms broader domain of continuous structure, such as Fddd and Gyroid. Frustrated system means XacN is much smaller than XbcN and XabN which cause component A and C to approach each other. To deeply understand the phase behavior of frustrated system, we select Fddd to decrease the XacN. Since the driving force of phase equilibrium is dominating factor change from internal energy to etropic energy, and the series of transition is FdddC/B→GC/B→CC/B. Finally, the phase diagram of frustrated system are constructed and variety of microstructures are found, including knitting pattern, perforated layer and helical superstructures. The component A and C tend to approach each other to offer different chain conformation such as folding. Since C block is pulled by two neighboring blocks, the curvature between B and C components changes quickly. This is why the morphology in linear ABCBA pentablock terpolymer is more abounded than in linear ABC triblock terpolymer in frustrated system.