固體表面吸附高分子常被用於控制介面的物化特性，例如，膠體粒子的位阻穩定或者絮凝作用，表面改性以及生物增容作用，表面潤滑和耐磨性能。在分子水準上，促進高分子吸附作用的機制包括：范德華作用，氫鍵相互作用，靜電作用和含表面結合位點的特殊相互作用。近年來，表面改性的研究熱點集中於尋找合適的方法，包括精確控制聚電解質刷的合成以及高分子吸附的選擇。然而，對於改性後的表面間相互作用的直接測定顯得相對滯後。這其中的原因主要是因為它們之間的相互作用太弱，無法用常規儀器測定。 / 本篇論文的主要目的是直接定量地測定固體表面吸附高分子和接枝完聚電解質高分子刷之後於水溶液中的弱相互作用。第一章主要介紹固體表面如膠體粒子間的相互作用，著重細緻討論了排空力，位阻排斥力，振盪結構力以及聚電解質刷所引起的作用力。在第二章中，我們探討了自行搭建的單粒子力學顯微鏡全內反射顯微鏡的歷史，發展及其原理。第三章闡述了表面改性中具體的化學方法。 / 第四章中，我們用直徑為5微米的聚苯乙烯小球作為探針，利用全內反射顯微鏡測定了不同的鹽溶液（氯化鈉和高氯酸鈉）對陽離子聚電解質刷（聚甲基丙烯醯氧乙基三甲基氯化銨）構象的影響。實驗結果顯示，高氯酸根與聚電解質刷的相互作用除了電荷遮罩作用外，還與聚電解質刷上的季銨鹽離子有強烈的離子配對作用能引起聚電解質刷失水造成“疏水折攏“。 / 在第五章中，我們主要運用全內反射顯微鏡研究了pH及離子強度變化對另一種陽離子聚電解質刷聚甲基丙烯酸二甲氨乙酯的溶脹作用的影響。對包覆了分子量為2000 g/mol的聚乙烯亞胺的聚苯乙烯微球以及表面改性了該種聚電解質刷之間的相互作用進行了直接測定。研究結果表明，聚電解質刷的鏈長，pH以及鹽離子強度對其作用影響很大。本實驗主要研究了兩種鏈長的聚電解質刷在溶液中的作用。對於較短的鏈長，在pH為4.2時，雙電層中的擴散層交疊排斥作用占主導且作用機理符合傳統的DLVO理論。但是，當pH逐步下降時，長程吸引作用開始出現。對於溶脹的較長鏈聚電解質刷，在高pH及低鹽離子強度時，其相互作用符合DLVO理論。然而，當降低pH或者提高鹽離子濃度時，作用勢能偏離DLVO理論，具體表現為：pH 4.0時為純靜電排斥作用，pH 3.6時出現弱吸引作用，pH 3.0時吸引變強，以上過程可循環往復。 / 第六章主要利用全內反射顯微鏡測定了一個微球與平整玻璃表面之間由聚環氧乙烷水溶液引起的相互作用。我們的結果展示了聚環氧乙烷吸附在兩固體表面上所引起的作用具有很強的濃度依賴性：在低濃度時，由靜電層排斥作用占主導；在較高濃度時，由聚合物橋接引起的長程吸引開始出現；在更高濃度時，我們檢測到額外的排斥作用出現，並推測是由於位阻排斥作用而非排斥的排空力作用引起；在繼續增大濃度後，我們觀察到了振盪結構力。 / Adsorption of polymers onto solid surfaces has often been used to control interfacial properties including steric stabilization or flocculation, surface modification and biocompatibilization, and lubrication as well as wear properties. In the molecular level, the mechanisms promoting polymer adsorption include attractive van der Waals forces, dipolar of hydrogen-bonding type attraction, electrostatic, or specific chemical interactions with surface binding sites. While a lot of efforts have been devoted in recent years to optimize the surface modification by synthesis of different types of polyelectrolyte brushes or polymers for adsorption, there have been few reports aimed at directly measuring the interaction forces between surfaces covered by the polymers and polyelectrolyte brushes in solution. This is not surprising because the forces of the interaction are extremely weak. / This thesis aims to directly and quantitatively study on the weak interaction between solid surfaces with adsorbed polymers and polyelectrolyte brushes in aqueous solutions. In the first chapter, the interactions between solid surfaces such as the colloidal particles are introduced. Specifically, forces such as depletion, steric repulsion, oscillatory structural forces and polyelectrolyte brushes induced forces are discussed in details. In the second chapter, we discuss about the historical background, development and principles of our recently home-made single particle force microscopy, Total Internal Reflection Microscopy (TIRM). The third chapter focuses on the synthesis of polymer brushes on solid surfaces. In this chapter, various chemical modification methods are covered. / In the fourth chapter, the conformational behavior of polyelectrolyte brushes in different electrolyte environments (NaCl and NaClO₄) has been investigated by directly measuring the interaction energy profile between a 5 m diameter polystyrene (PS) particle with a cationic poly (2-(methacryloyloxy)ethyl trimethylammonium chloride) (PMETAC) brush-grafted surface using TIRM. Our results show that ClO₄⁻ anions show strong ion paring with the quaternary ammonium groups on the polymer brushes, leading to what have called hydrophobic collapse where dehydration occurs in addition to pure charge screening. / In the fifth chapter, we applied TIRM to study the pH and ionic strength dependent swelling behavior of surface-grown cationic polyelectrolyte brush, poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA). As can be shown by direct force measurements between PDMAEMA grafted glass surface and PEI (polyethylene, Mw: 2000 g / mol) coat PS particle, the interactions are strongly affected by length of polyelectrolyte brush, pH values and salt concentrations. Polymer brushes with two different lengths are studied. For short polymer brushes, the interactions at pH 4.2 are dominated by repulsive forces originating from diffuse layer overlap, in line with the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). However, with decreasing the pH values, a long-range attraction sets in. For swollen and longer polymer bushes, the interactions are in a good agreement with the DLVO theory at high pH and low ionic strength. However, upon decreasing the pH value or increasing salt concentration, the inte actions show a significant deviation from DLVO theory. Specifically, the interaction between the particle and brushes-grafted surface can be switched reversibly between pure repulsion at pH 4.0, medium attraction at pH 3.6 and strong attraction at pH 3.0. / In the sixth chapter, TIRM was used to directly measure the interaction between a microsphere and a flat hydrophilic surface in the presence of polyethylene oxide (PEO) solution. Our results show that the PEO adsorption onto the solid surfaces is highly concentration dependent: at low polymer concentration, the interactions between two surfaces in the presence of PEO are dominated by repulsive forces originating from diffuse layer overlap; at intermediate polymer concentration, a long range and weak attraction sets in. We attribute the forces to the polymer bridging. While at high polymer concentration, an additional repulsive force is detected, and we believe this is not originated from repulsive depletion. But rather, our results suggest that this may due to the steric repulsion. Finally, at very high concentration, oscillatory structural force is detected. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wei, Xiaoling. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / 摘要 --- p.i / Abstract --- p.iii / Acknowledgement --- p.vi / Chapter Chapter 1. --- Background and Introduction --- p.1 / Chapter 1.1. --- Introduction to colloidal particles interaction --- p.1 / Chapter 1.2. --- Polymer induced forces in colloidal systems --- p.3 / Chapter 1.2.1. --- Steric repulsion --- p.3 / Chapter 1.2.2. --- Bridging interaction and depletion interaction --- p.4 / Chapter 1.2.3. --- Oscillatory structural forces --- p.7 / Chapter 1.2.4. --- Polyelectrolyte brushes induced forces --- p.9 / Chapter 1.3. --- Discussions --- p.11 / Chapter 1.4. --- Works in this thesis --- p.12 / Chapter 1.5. --- References and Notes --- p.13 / Chapter Chapter 2. --- Total Internal Reflection Microscopy (TIRM) --- p.16 / Chapter 2.1. --- Introduction --- p.16 / Chapter 2.2. --- Evanescent wave and total internal reflection --- p.17 / Chapter 2.3. --- Apparatus --- p.21 / Chapter 2.4. --- Data analysis --- p.25 / Chapter 2.5. --- Noise Analysis and Removal --- p.28 / Chapter 2.6. --- Interaction potentials; theory and TIRM measurement results --- p.30 / Chapter 2.7. --- References and Notes --- p.32 / Chapter Chapter 3. --- Surface Initiated Polymerization --- p.35 / Chapter 3.1. --- Introduction --- p.35 / Chapter 3.2. --- Living anionic polymerization --- p.36 / Chapter 3.3. --- Controlled radical polymerization methods --- p.36 / Chapter 3.3.1. --- Nitroxide-mediated polymerization --- p.37 / Chapter 3.3.2. --- Reversible addition-fragmentation chain transfer (RAFT) polymerization --- p.39 / Chapter 3.3.3. --- Atom transfer radical polymerization (ATRP) --- p.42 / Chapter 3.4. --- Experimentals --- p.46 / Chapter 3.5. --- Properties and applications of polymeric brushes --- p.48 / Chapter 3.6. --- References and Notes --- p.49 / Chapter Chapter 4. --- Ion-Induced Hydrophobic Collapse of Surface-Confined Polyelectrolyte Brushes Measured by Total Internal Reflection Microscopy --- p.56 / Chapter 4.1. --- Introduction --- p.56 / Chapter 4.2. --- Experimental Section --- p.58 / Chapter 4.3. --- Results and Discussion --- p.63 / Chapter 4.4. --- Conclusions --- p.75 / Chapter 4.5. --- References and Notes --- p.76 / Chapter Chapter 5. --- Direct Measurement of the Interactions between Polyelectrolyte Brush and Microsphere Studied by Using Total Internal Reflection Microscopy (TIRM) --- p.79 / Chapter 5.1. --- Introduction --- p.79 / Chapter 5.2. --- Experimental Section --- p.82 / Chapter 5.3. --- Results and Discussion --- p.89 / Chapter 5.4. --- Conclusions --- p.104 / Chapter 5.5. --- References and Notes --- p.105 / Chapter Chapter 6. --- Interactions between Solid Surfaces Mediated by Polyethylene Oxide (PEO): Concentration Effects --- p.109 / Chapter 6.1. --- Introduction --- p.109 / Chapter 6.2. --- Experimental Section --- p.112 / Chapter 6.3. --- Results and Discussion --- p.114 / Chapter 6.4. --- Conclusions --- p.126 / Chapter 6.5. --- Reference and Notes --- p.126 / Chapter Appendix --- p.130 / Chapter Experimental Section for the Swelling Ratio Calculation of PDMAEMA Brushes --- p.130 / Chapter References and Notes --- p.137 / List of Publications --- p.138 / Conferences and Symposiums Attended --- p.140

Active colloids, which can be thought of as the synthetic analog of swimming bacteria, exhibit remarkable collective behavior. Using a combination of computer simulations and analytical theory, I have looked to provide quantitative answers to fundamental questions concerning the phase behavior and material properties of active suspensions. A primary focus of my Ph.D work has been devoted to developing novel techniques to exploit the active nature of these particles to manipulate and self-assemble matter at the colloidal scale. In the introductory chapter, I discuss recent advances in the self-assembly of self-propelled colloidal particles and highlight some of the most exciting results in this field. The remaining chapters are each self-contained and focus on a particular topic within active colloidal self-assembly. These chapters are ordered in terms of system complexity, and begins with characterizing the thermomechanical properties of an ideal active fluid. The next three chapters are centered around characterizing the effective interactions induced by an active suspension. The last two chapters focus on using self-propulsion as a tool to improve colloidal self-assembly, and understanding the interplay between self-propulsion and anisotropic pair interaction.

No description available.

Hydrogels are three dimensional networks of hydrophilic homopolymers or copolymers generally covalently or ionically crosslinked. They interact with aqueous media by swelling to some equilibrium value by retaining the aqueous media in their structures. This study concerns the investigation of the swelling and the controlled drug release behaviour of hydrogels synthesized via the photopolymerisation process. The study of hydrogels in this project was oriented towards their biomedical applications as controlled drug delivery devices. It is a known fact that the complete conversion of monomers to polymers may not be achieved in the polymerisation process thus there is always a certain component of unreacted toxic monomers still remained in the polymer matrix. These monomers have the tendency to leach out of the polymer matrices when the polymers are in contact with an aqueous medium thus rendering the hydrogel to be nonbiocompatable. The polymers synthesized in this work were washed thoroughly in milli-Q-water and then evaluated in vitro for any possible toxic effect on human keratinocyte (HaCaT)v cells using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diaphenyl tetrazolium bromide (MTT) cell proliferation assay. The cytotoxicity results indicated that the hydrogels understudy sustained and allowed a positive growth of the HaCat cells in the duration of the cytotoxicity experiment, thus proving to be satisfactorily compatible. / Doctor of Philosophy (PhD)

Calcium alginate gels are widely used in the biotechnology, food, and pharmaceutical industries for cell immobilization, food additives, and controlling the release of therapeutic agents. Different gelation conditions can lead to different gel structures which affects the diffusion of solutes in gels, thus mathematical models were developed to describe diffusion and calcium alginate gel formation. This thesis on calcium alginate gel formation is divided into two parts, each with a mathematical model and corresponding experimental study. The objectives of this thesis were to: 1) Determine the significance of mass transfer resistance and estimate diffusion and mass transfer coefficients for calcium ions, glucose, and acetaminophen diffusing into calcium alginate gel. 2) Develop a moving boundary model of calcium alginate gel formation which predicts the rate of gelation. To study the significance of mass transfer resistance and to estimate coefficients, a mathematical model and limiting procedure were developed. This model and experimental study indicated that mass transfer resistance is significant for calcium ions and glucose, but not acetaminophen, diffusing into calcium alginate gel. The limiting algorithm developed to simultaneously estimate the diffusion and mass transfer coefficients is very sensitive to experimental error, but shows promise in situations with small numbers of accurate data points taken from non-interacting homogeneous gel systems. The model of calcium alginate gel formation was based upon a moving boundary problem, solved numerically using the implicit method of finite differences, and programmed in FORTRAN. This study of the rate of calcium alginate gel formation indicated that increasing the concentration of calcium ions and/or decreasing the concentration of alginate increases the rate of gelation. The predicted gelation rates from this mathematical model were in good agreement with the measured gelation rates based upon stoichiometric binding coefficients, experimental initial concentrations of calcium ions and alginate, and diffusion coefficients of Ca������ and alginate. / Graduation date: 1997

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Joel P. Schneider, Dept. of Chemistry & Biochemistry. Includes bibliographical references.

Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references (leaf 196).

Clay-rich glacial till aquitards are widespread throughout the northern hemisphere. Due to their low hydraulic conductivity, these geologic units are commonly used to contain wastes. Dissolved Organic Carbon (DOC) in natural environments influences the speciation and mobility of contaminants, such as heavy metals and radionuclides, and is present in high concentrations in clay-rich tills (5 to 150 mg l-1). Detailed knowledge of the influence of DOC on the long-term stability, speciation, and mobility of elements is lacking. Studies in this thesis characterize the properties and function of DOC with respect to element speciation and transport at the King research site, an archetypal clay-till aquitard in Saskatchewan, Canada. Characterization of DOC using Asymmetrical Flow-Field Flow Fractionation (AsFlFFF) with on-line UV and DOC detection demonstrated the molecular weight (Mw) of DOC within the aquitard environment is low, ranging from 1160 to 1286 daltons (Da), and the relative amount of aromatic carbon in aquitard DOC is lower than in surface water DOC. These findings imply the complexation ability of DOC in aquitards is lower than surface water DOC. DOC aromaticity decreased with depth in the aquitard, while Mw remained constant. DOC Mw in other aquitards investigated was comparably low (1470-1630 Da). Coupling AsFlFFF with on-line ICP-MS analysis allowed the identification of Fe, U and Zn associated with the DOC, and demonstrated that <4% of total aqueous elements tested at the King site were complexed with DOC. Experimental and numerical modeling results demonstrate the low masses of metals (Cu, Mn, Mo, Ni, Sr, U and Zn) complexed with the DOC can be attributed to competitive complexation with carbonate and sulphate ligands naturally present in the pore water. The in-situ association constant, Kd, for U and Zn as determined by complexation experiments decreased with depth in the aquitard and was attributed to the corresponding decrease in DOC aromaticity. The maximum mass of complexation of U and Zn to DOC takes place at pH 3-6, and decreases above and below this pH range (range tested: pH 1.3-10). These results were supported by geochemical modeling and suggest the complexation of aqueous metals by DOC should be limited in ground water environments of similar chemistries. Laboratory transport studies using double reservoir diffusion cells showed DOC and other similarly sized colloidal material can diffuse through the matrix at the King site aquitard. The effective pore throat diameter in the matrix media was determined to be 2 - 2.2 nm and travel times of colloids increased with increasing colloidal diameter. Colloids >2 nm were prevented from movement in the till by sieving mechanisms, which suggests bacteria and viruses as well as larger colloids should not migrate through till aquitards. Due to preferential sieving of larger Mw DOC, DOC in aquitard environments is typified by a small diameter compared with surface water DOC, and a small range in hydrodynamic diameter and Mw.

Clay-rich glacial till aquitards are widespread throughout the northern hemisphere. Due to their low hydraulic conductivity, these geologic units are commonly used to contain wastes. Dissolved Organic Carbon (DOC) in natural environments influences the speciation and mobility of contaminants, such as heavy metals and radionuclides, and is present in high concentrations in clay-rich tills (5 to 150 mg l-1). Detailed knowledge of the influence of DOC on the long-term stability, speciation, and mobility of elements is lacking. Studies in this thesis characterize the properties and function of DOC with respect to element speciation and transport at the King research site, an archetypal clay-till aquitard in Saskatchewan, Canada. Characterization of DOC using Asymmetrical Flow-Field Flow Fractionation (AsFlFFF) with on-line UV and DOC detection demonstrated the molecular weight (Mw) of DOC within the aquitard environment is low, ranging from 1160 to 1286 daltons (Da), and the relative amount of aromatic carbon in aquitard DOC is lower than in surface water DOC. These findings imply the complexation ability of DOC in aquitards is lower than surface water DOC. DOC aromaticity decreased with depth in the aquitard, while Mw remained constant. DOC Mw in other aquitards investigated was comparably low (1470-1630 Da). Coupling AsFlFFF with on-line ICP-MS analysis allowed the identification of Fe, U and Zn associated with the DOC, and demonstrated that <4% of total aqueous elements tested at the King site were complexed with DOC. Experimental and numerical modeling results demonstrate the low masses of metals (Cu, Mn, Mo, Ni, Sr, U and Zn) complexed with the DOC can be attributed to competitive complexation with carbonate and sulphate ligands naturally present in the pore water. The in-situ association constant, Kd, for U and Zn as determined by complexation experiments decreased with depth in the aquitard and was attributed to the corresponding decrease in DOC aromaticity. The maximum mass of complexation of U and Zn to DOC takes place at pH 3-6, and decreases above and below this pH range (range tested: pH 1.3-10). These results were supported by geochemical modeling and suggest the complexation of aqueous metals by DOC should be limited in ground water environments of similar chemistries. Laboratory transport studies using double reservoir diffusion cells showed DOC and other similarly sized colloidal material can diffuse through the matrix at the King site aquitard. The effective pore throat diameter in the matrix media was determined to be 2 - 2.2 nm and travel times of colloids increased with increasing colloidal diameter. Colloids >2 nm were prevented from movement in the till by sieving mechanisms, which suggests bacteria and viruses as well as larger colloids should not migrate through till aquitards. Due to preferential sieving of larger Mw DOC, DOC in aquitard environments is typified by a small diameter compared with surface water DOC, and a small range in hydrodynamic diameter and Mw.

No description available.