利用耗散粒子動力學探討ABC星狀高分子從弱聚集區域至強聚集區域的形態

Abstract

我們透過耗散粒子動力學(dissipative particle dynamics)來模擬具有許多豐富有趣結構的ABC星狀高分子(star copolymers)。我們觀察到結構深深受到組成與作用力參數的影響。我們固定彼此之間的作用力參數皆相等且在三成份組成比fA：fB：fC為1：1：X時，得到不同組成分在不同的作用力參數下的微結構變化，在本論文中，我們也將先前的理論計算方法，包括自洽場理論(self-consistent field theory, SCFT)與蒙地卡羅模擬方法(Monte Carlo simulations, MC)，一併納入比較。當組成fC 時，形成的結構主要為層狀或偶數邊數的柱狀結構，不太受到作用力參數所影響，這與MC於高作用力參數設定下和SCFT於較低作用力參數下的模擬結果一致。然而在fC 0.6，在高作用力參數下，少量的A、B為了降地彼此的排斥力，各自蜷曲成相互堆疊微胞排列，形成segmented wormlike micelles(SWM)，且隨著C組成的增加，結構從穿孔層狀或層狀互穿轉變成gyroid最後形成CHEX。這樣的結構目前雖然仍無法被實驗與理論計算證實，但透過文獻中poly(ethylethylene)-poly(ethylene oxide)-poly(perfluoropropylene oxide)(EOF)星狀高分子在以水為選擇性溶劑的實驗與模擬系統下，因著親疏水性的差異造成O鏈段膨潤(swelling)，E、F鏈段蜷曲，促使O的有效體積分率提升，形成長鏈的蟲形微胞(segmented wormlike micelles)結構，與我們在熔融態中提升組成比例有異曲同工的效用，且為了與實際的系統比較，我們也透過不對稱的作用力參數設定，得到類似於對稱作用力參數的結果，經由這樣的方式證實此結構的合理性。

We employ the dissipative particles dynamics (DPD) to examine the ABC star copolymers which enrich the interesting structures. The phase triangle of ABC star copolymer is built under the equal and moderate interaction parameters (a). The microphase-separated morphology variation in terms of the interaction parameter a and composition ratio 1：1：X. is also investigated in this work. We compare with the previous simulation techniques, including self-consistent field theory (SCFT) and Monte Carlo simulations (MC). The results are not merely similar, and more importantly, they display that the interaction parameter plays an indispensable role to the phase behavior. In addition, it is interesting that the peculiar segmented wormlike micelles in ABC star copolymer solutions are detected. Although this structure is still unable to be demonstrated in the melt at present, we verify the rationality of this structure via the experimental and theoretical system using poly(ethylethylene)- poly(ethylene oxide)-poly(perfluoropropylene oxide) (EOF) star copolymers in selective solvents. In addition, we also generalize that the morphology is influenced deeply by the length of the polymer chains at the lower interaction parameter. The longer chain will form the domains alone, and the shorter chain will mix each other or disperse in the interface.