利用自洽平均場理論探討ABn雜臂星狀共聚物在添加選擇性溶劑下的結構衍變

Abstract

我們利用自洽平均場理論，探討ABn星狀共聚物在添加選擇性溶劑下，觀察A鏈段組成f、共聚合物體積分率以及溶劑選擇性如何影響微結構衍變。當添加少量溶劑時，微結構衍變仍由組成f所控制；被溶劑討厭的那一方，隨著溶劑逐漸添加該成分會被包覆在曲面之內形成圓柱或球，若該成分組成較小，形成的是正常微結構；若該成分組成較大，則會形成反轉微結構。當我們添加對B鏈段具有選擇性的溶劑時，我們發現A鏈段被包覆在內形成之正常微結構與反轉微結構系統，皆會因為溶劑選擇性增加而穩定了A15微結構的存在；但是當我們添加對A鏈段具有選擇性的溶劑時，由於接點不完全在AB界面上的緣故，B鏈段被包覆在內的正常或反轉微結構系統皆沒有A15微結構存在。組成較大的A鏈段或B鏈段被包覆在內形成之反轉微結構，在高選擇性溶劑下，體心立方堆積球狀排列區塊會消失，取而代之的是A15微結構或是面心立方堆積球狀排列。當我們增加B鏈段分支數目n時，發現對於A鏈段被包覆在內之反轉微結構、B鏈段被包覆在內之正常或反轉微結構，其微結構衍變並無太大影響。

We employ the self-consistent mean-field (SCMF) theory in studying the phase behavior for ABn miktoarm star copolymers in the presence of a selective solvent. When the solutions are concentrated, the formation of equilibrium morphology is still mainly dominated by the composition f. When the B-selective solvent is added, the A15 structure will be more stable with increasing the solvent selectivity in both normal and inverted structure systems formed by A blocks. But when the A-selective solvent is added, because the junction point of the star copolymer does not all stay in the AB interface, the A15 structure does not exist in both normal and inverted structure systems formed by B blocks. In the inverted structure formed by the majority systems, BCC structure will vanish and be replaced by A15 or FCC structures under high solvent selectivity. In the A-formed inverted, B-formed normal and inverted structures, the phase behavior does not have significant effect with increasing the number of B blocks n.