聚丙烯酸與離子型界面活性劑作用之熱力學性質探討

Abstract

本研究的第一部分是利用毛細管動黏度實驗裝置研究聚丙烯酸溶液在溫度 298K 及 308K 之濃度區間，並檢視恆溫滴定熱卡計之實驗結果，觀察在不同聚丙烯酸溶液濃度區間，是否對聚丙烯酸/十六烷基三甲基溴化銨作用機制造成影響。結果顯示在我們所做的濃度範圍並無太大影響。 第二部分是希望藉由高靈敏度恆溫滴定熱卡計，測得聚電解質聚丙烯酸與陽離子型界面活性劑十六烷基三甲基溴化銨形成混微胞的各個轉折濃度及焓變化，研究的溫度範圍為 298 ~ 318 K。再探討各項變因，諸如聚丙烯酸濃度、聚丙烯酸分子鏈長(分子量)及溫度對於聚丙烯酸/十六烷基三甲基溴化銨系統之影響。結果顯示系統有一快速的放熱反應產生，而且聚丙烯酸鏈長不同會影響系統作用機制。 第三部份，我們則利用恆溫滴定熱卡計研究聚電解質聚丙烯酸與陰離子型界面活性劑十二烷基硫磺酸鈉形成混微胞之各個轉折濃度及焓變化，研究的溫度範圍為 288 ~ 318 K。再利用熱力學的關係，計算並討論聚丙烯酸/十二烷基硫磺酸鈉作用過程各種熱力學性質，諸如自由能變化及熵變化。再探討各項變因，如聚丙烯酸濃度及溫度對於聚丙烯酸/十二烷基硫磺酸鈉系統之影響。結果顯示聚丙烯酸/十二烷基硫磺酸鈉間吸附作用為焓驅動及熵驅動，且溫度會影響其臨界聚集濃度。

In the first part of this study, we examine the concentration regimes of poly(acrylic acid) solution by capillary viscometer. Then we check the effect of the concentration regimes on poly(acrylic acid)/tetradecyltrimethylammonium bromide interaction. However, for the poly(acrylic acid) concentration from 0.025 wt% to 0.075 wt%, there is no obvious difference between the poly(acrylic acid)/tetradecyltrimethylammonium bromide interactions in dilute or semidilute-unentangled regime of poly(acrylic acid) solutions. In the second part, the interaction between anionic polyelectrolyte, poly(acrylic acid) and cationic surfactant, tetradecyltrimethylammonium bromide has been investigated by isothermal titration calorimetry measurements. The addition of tetradecyltrimethylammonium bromide into poly(acrylic acid) aqueous solution demonstrates an exothermic peak due to the formation of poly(acrylic acid)/ tetradecyltrimethylammonium bromide complex driven by the electrostatic attraction and hydrophobic properties between oppositely charged poly(acrylic acid) and tetradecyltrimethylammonium bromide. As poly(acrylic acid) molecular weight decreases to 1800 g/mol, tetradecyltrimethylammonium bromide is not able to form mixed-micelle complex with poly(acrylic acid). In the third part, the interaction between poly(acrylic acid) and anionic surfactant, sodium dodecyl sulfate has been investigated by isothermal titration calorimetry measurements. Sodium dodecyl sulfate can form micelles on poly(acrylic acid) chain due to hydrophobic effect, even there exits electrostatic repulsion between them. This interaction is both enthalpy-driven and entropy-driven.