膠體顆粒吸附在油水介面的現象最近幾年引起極大的關注。一方面，受限在油水介面的膠體顆粒可以用作一個很好的模型體系來研究一些基本物理問題，例如二維結晶，擠壓以及其它相轉變問題。另一方面，在許多工業產品和處理過程中，例如食品，抗沫劑製備，以及原油乳液處理中膠體顆粒在油水介面的行為扮演著極為重要的角色。 / 微凝膠，一種軟膠體顆粒，也可以作為乳化劑用來穩定製備乳液。微凝膠在許多方面和普通膠體顆粒有著相同的行為。但是，微凝膠顆粒，作為一種三維交聯的高分子網狀鏈，在良性溶劑裡會膨脹。之前已經有報導明確指出這種微凝膠顆粒可以用來穩定的乳液。並且這些乳液的穩定性可控，此性質在小分子乳化劑和普通膠體顆粒體系是無法實現的。但是，這些微凝膠顆粒製備的乳液的穩定以及不穩定的作用機制至今尚有許多爭論。具體來說，這些微凝膠是如何吸附到油水面，什麼因素控制著這些吸附行為，微凝膠在油水介面如何行為，吸附在油水介面的微凝膠如何動態的回應外界條件的改變，統統不清楚。 / 本論文首先旨在深入瞭解微凝膠在油水介面的動態行為，然後用這些微凝膠穩定的乳液作為範本製備出多功能材料。本論文一共包括八部分，這八部分全部圍繞著微凝膠在油水介面的行為而展開。第一部分將介紹微凝膠應用在油水介面的研究已經取得的進展。第二部分將介紹彎曲的油水介面以及本論文主要用到的儀器。在第三部分，我們將會介紹微凝膠的製備與表徵。第四部分，我們集中於微凝膠是如何吸附到油水介面。我們發現微凝膠的柔軟，稀鬆，以及可變形決定了微凝膠的吸附過程。第五部分，我們探討為什麼油水介面動態張力在微凝膠的相轉變溫度附近有個最低值。通過對介面張力，溫度還有時間進行三維作圖，我們發現介面張力在微凝膠相轉變溫度附近(308.1K) 存在一個峰穀。這個峰谷的形成是由微凝膠的變形性以及它們之間相互作用所導致的。這些微凝膠吸附在油水介面之後形成一個新的微凝膠膜隔離開水與油，這層微凝膠險主導著油水介面的性質。第六部分，基於以上理解，我們在相轉變溫度附近創建了一個微凝膠未鋪滿的油水介面來研究微凝膠顆粒在一個受限的環境下的溫敏性行為。降低溫度，微凝膠在油水介面經歷一個極慢的舒張過程。但是升高溫度，微凝膠並沒有塌縮。第仁部分，我們首先應用微凝膠作為唯一穩定劑製備了一種高內相乳液，然後以此乳液為範本製備了多功能材料。最後一部分，縱觀全文，我們的結論是微凝膠的變形性以及它們之間的相互作用對於微凝膠在油水介面的行為起著非常重要的角色:包括微凝膠在油水介面的吸附行為，微凝膠在油水介面的溫敏性行為，油水介面的流變性能以及多功能材料的性能。 / The adsorption phenomena of colloidal particles at the liquid-liquids interfaces have received tremendous interests in recent years. On the fundamental side, interest stems from the fact that colloidal particles confined to the interfaces can serve as an elegant system for fundamental studies of physical processes, such as two-dimensional crystallization, jamming and other phase transitions. On the practical side, interest arises as a result of demonstrated importance of the behavior of colloidal particles at the interfaces for applications in many industrial products and processes such as the production of food, anti-foam formulations, and crude oil. / In recent years, soft particles, like microgels are also employed as emulsifiers for making emulsions. These microgel particles resemble colloidal particles in many aspects. However, structurally, microgel particles constitute a three-dimensional covalently crosslinked network and can swell up in good solvents. It has been reported that emulsions stabilized by these soft microgel particles can offer an unprecedented degree of control of emulsion stability, well beyond what can be achieved by using small molecular surfactants or conventional particles. However, the stabilization and destabilization mechanism involving such soft and deformable microgels is still a matter of debate. Specifically, how microgels adsorb onto the oil-water interfaces; what parameters control the microgel adsorption; how these microgels behave at the interfaces; and how these microgels respond to environmental triggers after adsorption, are unclear. / This thesis aims at first gaining a fundamental understanding of the microgels dynamic behaviors at the oil-water interfaces, and then using this system to fabricate functional materials. This thesis contains eight parts; all of them are connected with soft microgels at the oil-water interfaces. The first part of this thesis introduces the soft microgels’ performance at the oil-water interfaces. The second part focuses on the curved oil-water interfaces and the instrument we will use in this thesis. In the third part, we will present the preparations and characterizations of microgels. The fourth part addresses the microgels adsorption behaviors at the oil-water interfaces. Our results clearly show that deformability of microgel particles plays a vital role in their adsorption behaviors at the oil-water interfaces. In the fifth part, we discuss why interfacial tension (γ) exhibits a minimum in the vicinity of PNIPAM-related microgel volume phase transition temperature (VPTT). Our results suggest that, this observed minimum can be attributed to highest deformability of microgels around VPTT as well as the interactions among the adsorbed microgels. Moreover, our results reveal that unlike conventional solid particles, the adsorbed microgels are not wetted by both oil and water. On the contrary, they will form an intruding microgel layer separating the oil and water phases, which ultimately dominates the oil-water interfacial properties. Based on the above understanding, in the sixth part, we create microgels partially covered oil-water interfaces, and investigate the microgels thermal behaviors under a confined condition. Our results show that microgels undergo an extremely slow swelling process at the oil-water interfaces. In addition, microgels would not collapse upon heating. In the seventh part of this thesis, we present the preparation of high internal phase emulsions (HIPEs) by solely using soft microgels as emulsifiers. Furthermore, we demonstrate that these microgels-stabilized HIPEs can be good templates for the preparation of hierarchical porous functional materials. Based on our investigations, in the final part, we summary the importance of microgel deformability and their interactions on microgels behaviors at the oil-water interfaces: including their adsorption dynamics, thermal-responsive behaviors, oil-water interfacial rheology properties and functional materials properties. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Zifu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / 摘要 --- p.I / ABSTRACT --- p.III / ACKNOWLEDGEMENT --- p.V / TABLE OF CONTENTS --- p.VII / Chapter CHAPTER 1 --- INTRODUCTION AND BACKGROUND --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.1.1 --- Surfactant-stabilized emulsions --- p.1 / Chapter 1.1.2 --- Particle-stabilized emulsions --- p.3 / Chapter 1.2 --- Microgels as particulate emulsifiers in Pickering Emulsions --- p.6 / Chapter 1.2.1 --- Literature survey of microgels at interfaces --- p.7 / Chapter 1.2.2 --- Discussions and conclusions --- p.16 / Chapter 1.3 --- Theme of this thesis --- p.18 / Chapter 1.4 --- References and Notes --- p.19 / Chapter CHAPTER 2 --- THE FUNDAMENTALS OF CURVED OIL-WATER INTERFACE --- p.21 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- Pendant drop tensiometer --- p.22 / Chapter 2.3 --- The dynamic interfacial tension --- p.26 / Chapter 2.3.1 --- Two surfactant adsorption mechanisms --- p.27 / Chapter 2.4 --- Investigation of one single interface --- p.29 / Chapter 2.4.1 --- Pure heptane-water interface --- p.30 / Chapter 2.4.2 --- Heptane-BSA protein solution interface --- p.35 / Chapter 2.5 --- Dilatation rheology --- p.41 / Chapter 2.6 --- Conclusions --- p.42 / Chapter 2.7 --- References and Notes --- p.43 / Chapter CHAPTER 3 --- SYNTHESIS AND CHARACTERIZATION OF PNIPAM-RELATED MICROGELS --- p.45 / Chapter 3.1 --- Introduction --- p.45 / Chapter 3.2 --- Microgels preparation and characterization --- p.56 / Chapter 3.2.1 --- Preparation of microgel samples used in this thesis --- p.57 / Chapter 3.2.2 --- Microgels characterization --- p.59 / Chapter 3.3 --- Conclusions --- p.63 / Chapter 3.4 --- References and Notes --- p.63 / Chapter CHAPTER 4 --- MICROGEL ADSORPTION BEHAVIORS AT THE OIL-WATER INTERFACES: THE KINETIC STUDY --- p.65 / Chapter 4.1 --- Introduction --- p.65 / Chapter 4.2 --- Results and discussions --- p.67 / Chapter 4.2.1 --- The effect of microgel concentration: below VPTT --- p.68 / Chapter 4.2.2 --- Microgel concentration effect on dynamic interfacial tension: above VPTT of microgels --- p.73 / Chapter 4.2.3 --- Temperature effect on dynamic interfacial tension well above VPTT --- p.78 / Chapter 4.2.4 --- Diffusion controlled process --- p.81 / Chapter 4.2.5 --- Kinetic controlled process --- p.85 / Chapter 4.3 --- Conclusions --- p.93 / Chapter 4.4 --- References and Note --- p.95 / Chapter CHAPTER 5 --- ANOMALOUS INTERFACIAL TENSION VALLEYS DURING THE VOLUME PHASE TRANSITION OF PNIPAM MICROGELS AT THE OIL-WATER INTERFACE --- p.96 / Chapter 5.1 --- Introduction --- p.96 / Chapter 5.2 --- The interfacial tension valleys --- p.97 / Chapter 5.3 --- Discussions --- p.106 / Chapter 5.4 --- Conclusions --- p.115 / Chapter 5.5 --- References and Notes --- p.115 / Chapter CHAPTER 6 --- THE THERMAL BEHAVIOR OF MICROGELS CONFINED AT THE OIL-WATER INTERFACES: REVERSIBLE OR IRREVERSIBLE? --- p.117 / Chapter 6.1 --- Introduction --- p.117 / Chapter 6.2 --- Microgels thermal behaviors confined at interfaces --- p.118 / Chapter 6.3 --- Conclusions --- p.137 / Chapter 6.4 --- References and Notes --- p.138 / Chapter CHAPTER 7 --- FUNCTIONAL MATERIALS FROM MICROGELS AT INTERFACES --- p.139 / Chapter 7.1 --- High internal phase emulsions (HIPEs) --- p.139 / Chapter 7.2 --- Microgels stabilized HIPEs --- p.140 / Chapter 7.2.1 --- Preparations --- p.140 / Chapter 7.2.2 --- Characterizations --- p.141 / Chapter 7.3 --- Materials from microgels stabilized emulsions --- p.144 / Chapter 7.3.1 --- Porous membranes --- p.144 / Chapter 7.3.2 --- Hierarchical porous materials --- p.145 / Chapter 7.4 --- Conclusions --- p.146 / Chapter 7.5 --- References and Notes --- p.147 / Chapter CHAPTER 8 --- OVERVIEW OF MICROGELS AT INTERFACES --- p.148 / Chapter 8.1 --- Summary of microgels at interfaces --- p.148 / Chapter 8.2 --- Outlook and further experiments --- p.150 / CURRICULUM VITAE --- p.152
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328133 |
| Date | January 2012 |
| Contributors | Li, Zifu., Chinese University of Hong Kong Graduate School. Division of Chemistry. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (ix, 154 leaves) : ill. (some col.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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