本篇論文主要以一種介觀尺度下的模擬方法-分散粒子動力學（Dissipative particle dynamics）來探討於poor solvent中可彎曲式高分子和硬桿式高分子與界面活性劑之作用。 在good solvent中，可彎曲式高分子與界面活性劑之作用機制，過去的研究通常採用珍珠項鍊模式（pearl-necklace model）來描述。對於高分子於poor solvent中，珍珠項鍊模式是否依然滿足？而硬桿式高分子，如奈米碳管，在光電材料中有良好的應用。其於溶液中的懸浮在工業上為極重要的課題。 本文主要分為兩部分，在探討高分子與界面活性劑作用之前，我們會先研究各種不同界劑性質，如：親水頭基長度、疏水尾鏈長度、尾鏈分支及尾鏈硬度，對臨界微胞濃度的影響。並且證明此模擬系統與實驗結果相符。第二部分則研究於poor solvent中，可彎曲式高分子和硬桿式高分子與界面活性劑之行為表現。模擬結果顯示，可彎曲式高分子在poor solvent中，彼此糾結捲曲成球形。隨著界面活性劑濃度增加，吸附在高分子上的界面活性劑也越多，最後達到飽和被包覆在微胞裡，而不滿足珍珠項鍊模式。 硬桿式高分子在poor solvent中會彼此聚集在一起。添加疏水尾鏈較短的界面活性劑時，會使其分散懸浮。隨著疏水尾鏈變長，高分子與界面活性劑因彼此纏繞而無法懸浮。當硬桿式高分子與界面活性劑間無特別作用力存在時，經過攪拌後，其會穩定懸浮一段時間，處於一介穩態，證明與實驗結果相符。 The polymer-surfactant interaction in poor solvent is studied by dissipative particle dynamics (DPD) simulations. The polymer-surfactant interaction leads to the formation of polymer-surfactant complex. For flexible polymer in good solvent, the necklace morphology is well accepted. The purpose of this work is to examine whether the polymer-surfactant complex in poor solvent follows the necklace model or not. Both flexible and rigid polymers are considered. The motivation for studying the latter case is because most applications employing the unique electronic, thermal, optical, and mechanical properties of carbon nanotubes require the large-scale manipulation of stable suspensions in water at high weight fraction by surfactant addition. The stability of rigid polymer-surfactant complex therefore becomes an important issue. This thesis involves two topics. In the first topics, the surfactant characteristics are explored. The influence of molecular structure on the surfactant property in terms of critical micelle concentration (CMC) is investigated at the same interaction parameters. The surfactant structures are changed by altering head group length, tail length, tail rigidity, and tail architecture. The qualitative behavior of CMC determined by DPD agrees with that of experimental results. In the second topic, the adsorption behavior of surfactant onto polymer in poor solvent is investigated. Although a flexible polymer collapses into a globule in poor solvent, it is swollen and wrapped within a micelle upon addition of surfactant. The rigid-polymers tend to aggregate into a buddle in poor solvent. Nonetheless, upon addition of surfactant with short tail, which has specific interactions with polymer segment, the rigid-polymers disperse stably in the solvent due to the coverage of surfactant. A large micelle is formed to enclose the rigid-polymer and thus the necklace model is invalid in poor solvent.
