聚電解質/界面活性劑系統在不同中和度下之熱力學與黏度性質探討

Abstract

聚電解質以及聚電解質/界面活性劑系統因其獨特的溶液性質及可調控性被廣泛的研究及運用於工業上。本研究中將探討在不同中和度下，聚電解質之黏度性質及聚電解質/界面活性劑之熱力學性質與特徵濃度。 本研究由落球式黏度計量測陰離子型聚電解質聚丙烯酸 (PAA) 溶液之黏度，並加入氫氧化鈉溶液改變其中和度，並討論中和度以及分子量對黏度性質之影響。實驗結果為中和度越高，黏度越大，並且短鍊 PAA 在有增加中和度的情況下，其黏度性質會更為符合 Scaling theory，重疊濃度下降、纏繞濃度上升，可以說其黏度性質變得更像「聚電解質」了。 聚電解質/界面活性劑系統則是想探討聚丙烯酸 (PAA) 與陽離子型界面活性劑十六烷基三甲基溴化銨 (C16TAB) 之間的作用力與機制，改變系統中和度以探討其影響。使用了恆溫滴定熱卡計 (ITC)、表面張力儀、pH 計、界面電位儀，並觀察溶液之混濁度與沉澱情形。由實驗結果得知，在帶相反電性的 PAA/C16TAB 系統中，靜電作用力和疏水作用力共同形成鍵結和混微胞。隨著中和度的增加，PAA 解離出更多氫離子，使更多的 C16TAB 分子鍵結在鍊段上，臨界聚集濃度下降；沉澱點、飽和濃度、自由微胞濃度等特徵濃度均大幅上升。短鍊 PAA 在有增加中和度的情況下，沉澱更加明顯，呈現塊狀白色沉澱。這是由於 PAA/C16TAB 複合物的分子量因鍵結了更多 C16TAB 而顯著增加，使 PAA 呈現出類似帶有大量碳鍊支鍊的構型，使各複合物之間產生更強的纏繞，且粒子不帶電難以穩定分散，最終形成明顯的沉澱。

The polyelectrolyte/surfactant (PES) system has been researched for a long time. Due to its unique properties and controllability of PES mixed micelles, it could be applied in solution modification, wastewater treatment, enhanced oil recovery, etc. This study will discuss the rheological properties of polyelectrolytes and the thermodynamic properties of polyelectrolyte/surfactant systems at different degrees of neutralization. The rolling ball viscometer was used to measure the viscosity of weak acid poly(acrylic acid) (PAA) solution at different degrees of neutralization, which is changed through titrating sodium hydroxide solution in the PAA solution. The viscosity increased as degrees of neutralization increased. We also noticed that the rheological behaviors of short-chain PAA became much by the scaling theory, indicating that short-chain PAA became more like a “polyelectrolyte” through adding NaOH. In this study, we used an isothermal titration calorimeter (ITC), tensiometer, pH meter, and zeta sizer to measure the data of PAA and Hexadecyltrimethylammonium bromide (C16TAB) at different degrees of neutralization. The result showed if the degree of neutralization increases, CAC decreases, and Cp, Cs, Cm increase. The electrostatic interaction would get stronger.