PAMAM樹狀體與SDS界面活性劑靜電錯合物之奈米結構研究

高分子與兩性界面活性劑 (amphiphilic surfactant) 的錯合物可透過極性(由高分子主鏈和界面活性劑頭基所構成)以及非極性(界面活性劑的烷鏈)之間的微相分離提供一個簡易的途徑來形成具長程有序之奈米結構。先前的研究主要集中在界面活性劑與線性高分子的錯合物，主要觀察到的結構為平坦界面的層狀結構。本研究探討質子化後帶正電的poly(amidoamine) 樹狀體(簡稱PAMAM樹狀體)與帶負電的界面活性劑十二烷基硫酸鈉 (Sodium dodecyl sulfate, SDS) 以靜電作用力形成錯合物。我們透過NMR光譜來量測錯合物之實際組成 (xa)，結果顯示靜電錯合有效的發生。小角度X光散射 (SAXS) 結果顯示，隨著SDS鍵結比例增加，錯合物會由體心立方堆積 (body centered cubic phase) 結構轉變成六面堆疊圓柱 (hexagonal columnar phase) 結構再轉變成面心矩形柱狀 (centered rectangular columnar) 結構，最後轉為傾斜柱狀 (oblique columnar phase) 結構。由Cryo-TEM的影像可以觀察到，SDS所形成的柱狀結構中，沿著柱狀長軸的方向仍然保持樹狀體分子的曲率而形成特殊的波動柱狀結構。本研究可揭露，我們可以藉由操控界面活性劑鍵結的比例並利用樹狀體的幾何特性產生各種具界面波動的柱狀有序形態。

關鍵字

樹枝狀高分子；界面活性劑；靜電錯合物；波動柱狀相

並列摘要

The complexation of polymer with amphiphilic surfactants offers a facile route for constructing long-range ordered nanostructures via microphase separation between the polar (composed of the polymer backbone and surfactant headgroup) and the nonpolar (surfactant alky tail) components. Previous studies on this type of supramolecule have been centered on the complexes of surfactants with linear polymers, where the lamellar structure with flat interface had been predominantly observed. In this study, we demonstrate that the electrostatic complexation of a surfactant with an oppositely charged 3D polymer, dendrimer, yielded the long-range ordered columnar nanostructures with undulated interface, where the nonzero interfacial curvature was imparted by the intrinsic geometric feature of the dendrimer. Here an anionic surfactant, sodium dodecyl sulfate (SDS), was complexed with protonated G4 poly(amidoamine) (PAMAM) dendrimer whose positive charge density was prescribed by degree of protonation (dp). The actual binding ratio (xa) of the SDS to the dendrimer measured by NMR spectroscopy revealed that the electrostatic binding between two components in aqueous solution occurred cooperatively. The SAXS results revealed the transition of the mesomorphic structure of the complex with respect to the increase of xa, where the structure transformed from body-centered cubic phase (Im"3" ̅m) to hexagonal columnar phase (p6mm), and then to centered rectangular columnar phase (c2mm) with the columns formed by SDS. When xa nearly reached the stoichiometric value, i.e., xa ≌ 1.0, an oblique columnar phase (p2) was formed. Cryo-TEM observation revealed that the interface of the SDS cylindrical micelles was undulated. The present study has thus demonstrated the power of dendrimer as the supramolecular building block for constructing columnar mesophases with various packing symmetries and further conferring undulated interface to the cylindrical micelles composed of the surfactant.

並列關鍵字

dendrimer ； surfactant ； electrostatic-complex ； undulated-columnar-phase

參考文獻

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國際替代計量

PAMAM樹狀體與SDS界面活性劑靜電錯合物之奈米結構研究

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