硅對現今科技至關重要。而有機物吸附於硅表面可能大大擴展硅的用途。在本論文中，我採用密度泛函理論研究了六種分子於硅表面的反應。本論文大致可分為四部分。 / 第一部分包含四個分子（吡嗪、吡啶、嘧啶與1,3,5-三氮嗪）的吸附研究。它們都擁有類似於苯的結構而環中又包含氮原子。分子可以用氮原子與表面形成配位鍵並作為進一步反應的前體故其反應更為容易預測。而反應通常只消除π 鍵而不會使分子分解這使得分子可以在平衡狀態下與表面生成最為穩定的結構。此兩種特性使它們成為硅表面吸附的絶佳研究對象。不同的實驗都顯示出吡嗪於硅表面只會生成Cross-row bridge 結構加熱硅表面更會促進納米線的生成。過往的計算無法解釋實驗結果而我的計算表明范德華力對導出正確計算結果非常重要加入范德華力的修正可以同時解釋單一產物與納米線的生成。吡啶的吸附實驗結果相比之下較為複雜。低溫下的吸附與飽和只生成兩種產物可是室溫下的實驗卻顯示多種產物並存於表面。加入范德華力的計算結果指出覆蓋度和溫度與吸附密切相關並指出對低溫下形成的飽和表面加溫可能促使納米線的生成。而於室溫下吡啶可進入多條反應路徑致使多種產物於表面並存。基於范德華力對這兩個分子的顯著影響我又將此效應加諸於嘧啶與1,3,5-三氮嗪的吸附研究。結果表明於低覆蓋度與低溫下它們只生成Double-dative 產物。然而增加覆蓋度會使Double-dative 的能量高於其它產物導致多種產物並存。由於嘧啶與1,3,5-三氮嗪都可生成一種特別的tight-bridge 結構加溫會使它們輕易解離。對此四種分子的研究顯示出氮原子的數量與位置如何影響吸附過程。 / 第二部分包含對1,2-環己二酮的吸附研究。於室溫下此分子會以互變異構體形式存在。之前的實驗指出它會先變回二酮才進行後續反應這種硅表面輔助互變反應的現象是前所未見的卻無後續研究以驗証其說。我的計算結果指出雖然互變反應的能壘被硅表面大幅降低可是仍不足以與其他反應路徑相匹敵。其中三種新產物既與實驗譜相吻合而反應能壘和能量都低故比之前所提產物更為可取。 / 第三部分包含對氰基苯的吸附研究。之前的三個實驗給出完全不同的結論。探明其與覆蓋度和溫度的關係後我提出氰基苯於低溫下飽和只會生成一種產物。而在室溫下的吸附會先生成valley-bridge 結構增加覆蓋度將使多種產物並存。計算結果不但表明有序吸附的可能性同時又解釋為何不同實驗給出看似不相容的結論。 / Silicon is an important material and substrate in modern technologies. Adsorption of organic molecules on silicon surface has attracted much attention due to the possibility of functionalizing the surface. In this thesis, density functional theory has been applied to study the adsorption of several organic molecules on Si(100) surface. / Results on the adsorption of benzene-like N-heteroaromatic molecules on Si(100)surface, including pyrazine, pyridine, pyrimidine and s-triazine, are presented in Chapters 2-4. This class of molecules, containing nitrogen atoms, can datively attach to dimer and act as precursor for further reaction. Thus, their reactions on surface can be easily predicted. Their reaction with surface would sacrifice π bond rather than dissociation under very mild condition such that the most stable adsorption product can be obtained under thermal equilibrium. These two properties of N-heteroaromatic compounds makes them good models for the study of reaction on surface Experiments repeatedly showed that pyrazines formed cross-row bridge structures on Si(100) under various conditions, and thermal annealing led to the formation of ordered nano-lines. Previous calculations did not explain these observations. This thesis demonstrates that addition of van der Waals (vdW) correction is critical to explain the formation of both the cross-row bridge and the nano-lines. For pyridine, the situation is more complex. Only two products were observed in low temperature adsorption experiments. In contrast, room temperature experiments yielded a mixture of products. With vdW corrections added, results show that pyridine adsorption is dependent on both coverage and temperature. Adsorption and saturation started at low temperature and followed by annealing may produce nano-lines consisted of cross-row bridge structures. Adsorption at room temperature opens up all reaction channels such that nano-line formation becomes difficult, which explains the discrepancy among experimental studies. In light of these results, the pyrimidine and s-triazine adsorption on Si(100) are also explored. The results show that they form double-dative structures at low coverage and low temperature. Increasing coverage will destabilize it and lead to mixture of products. These structures decompose easily upon heating due to the formation of a particular tight-bridge structure. These results show that the position and number of heteroatom are important to explain the difference in reaction selectivity among N-heteroaromatic molecules. For all four molecules, cooperative effect and the addition of vdW correction, which are almost neglected in similar study, are shown to be important in surface adsorption process. / In Chapter 5, the adsorption of 1,2-cyclohexanedione (1,2-CHD) on surface is studied. Gas molecule of 1,2-CHD exists in the tautomeric form (2-hydroxylcyclohex-2-ene-1-one) at room temperature. Previous experimental studies claimed that surface assisted tautomerization back to 1,2-CHD took place before further reaction, although there was no follow-up study. Computational results showed that although surface adsorption lowers the barrier for tautomerization, the barrier is still at least 5 times larger than other reaction channels. Three new structures are proposed, which are in better agreement with previous spectroscopic results. / In the final chapter, the adsorption of benzonitrile on Si(100) is studied. Three previous experimental studies presented conflicting results. With the coverage and temperature dependence effects clarified, my results suggest that adsorption at saturation and low temperature leads to a single product. Adsorption at room temperature first leads to a valley-bridge structure, while a mixture of adsorption structures is produced upon increasing coverage, which explained the conflicting experimental results. The last two chapters show the importance of computational modeling for interpretation and summarizing experimental results. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ng, Kwok Hung. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references. / Abstracts also in Chinese. / Ng, Kwok Hung.

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

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Thesis (Ph. D.)--University of Delaware, 2006. / Principal faculty advisor: Andrew V. Teplyakov, Dept. of Chemistry & Biochemistry and Raul F. Lobo, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis ( Ph.D. ) -- University of Texas at Arlington, 2008.

Thesis (M.S.) in Chemical Engineering--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 77-79).

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