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研究生： 洪慧芳
Ｈui-Fang Huang
論文名稱： 氧化鋯奈米粒子在聚甲基丙烯酸酯薄膜分散、聚集及偏析行為
Dispersion, Aggregation and Segregation Behaviors of Zirconia Nanoaprticles within Poly(methyl methacrylate) Thin Films
指導教授： 孫亞賢
Ya-Sen Sun
口試委員:
學位類別： 碩士
Master
系所名稱： 工學院 - 化學工程與材料工程學系
Department of Chemical & Materials Engineering
畢業學年度： 99
語文別： 中文
論文頁數： 138
中文關鍵詞： 偏析 、聚集 、分散 、聚甲基丙烯酸 、氧化鋯
外文關鍵詞： dispersion, Poly(methyl methacrylate), Zirconia Nanoaprticles, aggregation, segregation
相關次數： 點閱：13  下載：0 
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    • 本研究探討表面接枝不同鏈段長度的羧酸氧化鋯奈米粒子於不同分子量聚甲基丙烯酸酯薄膜(PMMA)中的分散、聚集及偏析行為，依據碳鏈長短，所使用的羧酸有甲基丙烯酸(Methacrylic acid, MA)、丁酸(Butyric acid, BA)、亞麻油酸(Linoleic aicd, LOA)三種接枝鏈。同時也改變聚甲基丙烯酸酯分子量，進而探討這三種接枝鏈段影響氧化鋯奈米粒子在聚甲基丙烯酸酯聚集行為之熱力學機制。
    接枝相異鏈段的氧化鋯粒子與均聚物甲基丙烯酸酯之間有不同的相容性，其中接枝鏈段為甲基丙烯酸和丁酸與甲基丙烯酸酯的相容性較佳，相對的，接枝鏈段為亞麻油酸的氧化鋯粒子其相容性最差，因為亞麻油酸的接枝鏈段與均聚物甲基丙烯酸酯之間不相互容，使得氧化鋯粒子彼此聚集成團聚物，此三種相容性差異造成MA-ZrO2 及BA-ZrO2在PMMA高分子中以團聚物的形式分散及LOA-ZrO2 在PMMA高分子中呈現團聚物聚集的形式。
    藉由熱回火處理，接枝不同鏈段種類的氧化鋯粒子會聚集成不同尺寸的團聚物，團聚物的種類上有線狀、圓盤狀以及趨近於球狀等結構。然而相容性最差的LOA-ZrO2 不僅會聚集成大尺寸的圓盤狀團聚物，在熱回火過程還會形成奈米尺度的內連結圓盤狀聚集結構，同時也形成微米尺度的非潤濕結構，此時LOA-ZrO2會偏析至薄膜高低起伏的邊緣處聚集，降低PMMA鏈段的伸展熵，這是接枝亞麻油酸鏈段的氧化鋯粒子較為特殊的現象。
    不同羧酸氧化鋯奈米粒子混摻聚甲基丙烯酸酯製備出的複合材料經過熱回火處理有不同表面形態，LOA-ZrO2混摻PMMA製備出的奈米複合材料會產生非潤濕結構，相對的，MA-ZrO2或BA-ZrO2製備出的奈米複合材料則會均勻潤濕在矽基板上。

    In this work, I investigated organic-inorganic thin films of poly (methyl methacrylate) (PMMA) homopolymers of three molecular weights (MWs, Mn =17, 45 and 105 kg/mol) hybridized with zirconia nanoparticles (ZrO2 NPs). Prior to mixing with PMMA, the ZrO2 NPs were surface-modified by grafting a layer of various carboxylic acids (methacrylic acid, butyric acid and linoleic acid). For brevity, the surface-modified ZrO2 NPs were designated as MA-ZrO2, BA-ZrO2 and LOA-ZrO2. In the following context, I systematically studied the dispersion, aggregation and segregation behaviors of surface-modified ZrO2 NPs within the PMMA thin films.
    The dispersion, aggregation and segregation behaviors of carboxylic acid-grafted ZrO2 NPs within PMMA homopolymers depend on the enthalpic effect. According to the solubility parameters, I proposed that the MA or BA dispersants are miscible with PMMA whereas LOA is immiscible with PMMA. The former cases revealed the dispersion of small MA- and BA-ZrO2 clusters within PMMA homopolymers whereas the latter case was found to form large aggregates. The formation of the large aggregates is ascribed to reducing the unfavorable contacts between LOA-ZrO2 NPs and PMMA chains. Additionally, the ZrO2 NPs with surface grafted by a layer of LOA were found to preferentially segregate to the boundaries of cracks within the LOA-ZrO2/PMMA films. As a result, the conformational entropy loss associated with stretching of PMMA chains could be minimized.
    Moreover, LOA has the lowest surface energy. It is likely that LOA-ZrO2 nanoparticles preferentially aggregate to the free surface of poly (methyl methacrylate) thin films when thermal-annealing were implemented at a high temperature far above the glass transition temperature of PMMA. As a result, the thermal-annealed LOA-ZrO2/PMMA thin films revealed a morphology of dewetting. By contrast, the thin films of MA-ZrO2/PMMA and those of BA-ZrO2/PMMA still revealed homogeneous in thickness (i.e., fully wetting) on substrates.

    摘要......................................................I Abstract................................................III 致謝.....................................................V 目錄....................................................VII 圖目錄...................................................XI 表目錄.................................................XIX 第一章 緒論.............................................1 第二章 簡介...............................................3 2-1 有機-無機奈米複合材料.................................3 2-2 應用..................................................6 2-2-1 自癒材料............................................6 2-2-2 化學氣體感應元件....................................7 2-2-3 有機-無機混層太陽能電池元件.........................8 2-2-4 LED封裝材料........................................10 2-2-5 抑制高分子薄膜非潤濕行為...........................11 2-3 無機奈米粒子於有機高分子中之分散行為.................13 2-3-1 奈米粒子的分散-尺寸效應............................13 2-3-2 接枝鏈-奈米粒子分散................................18 2-4 奈米粒子於均聚物中之聚集行為.........................20 2-4-1 系統熵之調控.......................................20 2-4-2 團聚物分散或偏析行為-尺寸及鏈長效應................24 2-5 奈米粒子於均聚物中之偏析行為.........................26 2-5-1 偏析行為之焓調控...................................26 2-5-2 偏析行為之熵、焓調控...............................27 2-5-3 奈米粒子雙嵌段共聚物的微相分離奈米結構之偏析行為...30 第三章 研究動機..........................................35 第四章 實驗部份..........................................36 4-1 實驗藥品與基材 .......................................36 4-2 實驗儀器.............................................39 4-3 實驗方法.............................................40 4-3-1 基材清洗...........................................40 4-3-2 均聚物PMMA高分子混摻羧酸改質氧化鋯奈米粒子的薄膜製備.......................................................40 4-3-3 穿透式電子顯微鏡試片製備...........................41 4-4 儀器分析.............................................42 4-4-1 光學顯微鏡.........................................42 2-4-2 穿透式電子顯微鏡...................................44 4-4-3 高解析X光反射儀....................................45 4-4-4 掠角式小角度X光散射................................48 第五章 實驗結果與討論....................................54 5-1 聚甲基丙烯酸酯均聚物(PMMA)及表面接枝羧酸氧化鋯粒子之團聚物尺寸探討.............................................54 5-1-1 聚甲基丙烯酸酯均聚物(PMMA)之盤旋半徑...............54 5-1-2 表面接枝羧酸氧化鋯粒子之尺寸探討...................56 5-2 接枝鏈與均聚物之相容性...............................60 5-3 氧化鋯奈米粒子於聚甲基丙烯酸酯薄膜之分布情形.........61 5-3-1 甲基丙烯酸-氧化鋯於聚甲基丙烯酸酯薄膜之分佈情形....61 5-3-2 丁酸-氧化鋯於聚甲基丙烯酸酯薄膜之分佈情形..........65 5-3-3 亞麻油酸-氧化鋯於聚甲基丙烯酸酯薄膜之分佈情形......68 5-3-4 偏析現象之探討.....................................71 5-4 氧化鋯團聚物尺寸及結構之探討.........................73 5-4-1 甲基丙烯酸-氧化鋯於聚甲基丙烯酸酯薄膜之結構探討....73 5-4-2 丁酸-氧化鋯於聚甲基丙烯酸酯薄膜之結構探討..........75 5-4-3 亞麻油酸-氧化鋯於聚甲基丙烯酸酯薄膜之結構探討......77 5-5 薄膜穩定性...........................................80 5-6 自由能效應...........................................88 5-6-1 系統焓之效應.......................................88 5-6-2 系統熵之效應.......................................89 第六章 結論..............................................91 第七章 參考文獻..........................................93 附錄....................................................102

    [1] C. Sanchez, B. Julia´n, P. Belleville, M. Popall " Applications of hybrid organic–inorganic nanocomposites " J Mater Chem, 15, 3559-3592, 2005.
    [2] C. Sanchez, H. Arribart, M. M. G. Guille "Biomimetism and bioinspiration as tools for the design of innovative materials and systems " Nature Materials, 4, 277-288, 2005.
    [3] P. Gómez-Romero, C. Sanchez "Hybrid materials. Functional properties. From Maya Blue to 21st century materials "New J. Chem., 29, 57-58, 2005.
    [4] C. Sanchez, G. J. de A. A. Soler-Illia, F. Ribot, T. Lalot, C. R. Mayer, and V. Cabuil "Designed Hybrid Organic−Inorganic Nanocomposites from Functional Nanobuilding Blocks" Chemistry of Materials, 13, 3061-3083, 2001.
    [5] U. Schubert, N. Huesing, A. Lorenz "Hybrid Inorganic-Organic Materials by Sol-Gel Processing of Organofunctional Metal Alkoxides" Chem. Mater., 7, 2010-2027, 1995.
    [6] Bruno Boury, Robert J. P. Corriu"Auto-organisation of hybrid organic–inorganic materials prepared by sol–gel chemistry" Chem. Commun., 8, 795-802, 2002.
    [7] G. J. de A. A. Soler-Illia, C. Sanchez, B. Lebeau, J. Patarin "Chemical Strategies To Design Textured Materials: from Microporous and Mesoporous Oxides to Nanonetworks and Hierarchical Structures" Chem. Rev., 102, 4093-4138, 2002.
    [8] R. J. P. Corriu, A. Mehdi, C. Reyé, C. Thieuleux "Control of coordination chemistry in both the framework and the pore channels of mesoporous hybrid materials" New J. Chem., 27, 905-908, 2003.
    [9] S. Guptal, Q. Zhangl, T. Emrick, A. C. Balazs, T. P. Russell "Entropy-driven segregation of nanoparticles to cracks inmultilayered composite polymer structures" Nature Materials, 5, 229-233, 2006.
    [10] M. L. Turner, B. R. Saunders, "Nanoparticle–polymer photovoltaic cells" Advances in Colloid and Interface Science, 138, 1-23, 2008.
    [11] R. Shenhar, T. B. Norsten, V. M.Rotello, "Polymer-Mediated Nanoparticle Assembly: Structural Control and Applications" Admance Materials, 17, 657-669, 2005.
    [12] B. Guse, T. Vossmeyer, I. Besnard, R. E. Bauer, K. Müllen, and A. Yasuda, "Gold Nanoparticle/Polyphenylene Dendrimer Composite Films: Preparation and Vapor-Sensing Properties" Admance Materials, 14, 238-242, 2002.
    [13] Nadejda Krasteva, I. Besenard, B. Guse, R. E. Bauer, K. Mu1llen, A. Yasuda, T. Vossmeyer, "Self-Assembled Gold Nanoparticle/Dendrimer Composite Films for Vapor Sensing Applications" Nano Letters, 2, 551-555, 2002.
    [14] D. C. Olson, J. Piris, R. T. Collins, S. E. Shaheen, D. S. Ginley, "Hybrid photovoltaic devices of polymer and ZnO nanofiber composites" Thin Solid Film, 496, 26-29, 2006.
    [15] B. Sun, H. J. Snaith, A. S. Dhoot, S. Westenhoff, N. C. Greenham, "Vertically segregated hybrid blends for photovoltaic devices with improved efficiency" Journal of Applied Physics, 97, 014914, 2005.
    [16] J. W. Kiel, A. P. R. E berle, M. E. Mackay, "Nanoparticle Agglomeration in Polymer-Based Solar Cells" Physical Review Letter, 105, 168701, 2010.
    [17] 陳俊郎、孫慶成, "LED 封裝與在內部量子效率的評估之研究," 2007.
    [18] K. Xu, S. Zhou, L. Wu, "Effect of highly dispersible zirconia nanoparticles on the properties of UV-curable poly(urethane-acrylate) coatings" Journal of Material Science, 44, 1613-1621, 2009.
    [19] M. E. Mackay, R S Krishnan, P M Duxbury, C J Hawker, S. Asokan, M. S Wong, R. Goyette, P. Thiyagarajan, "Improved polymer thin-film wetting behavior through nanoparticle segregation to interfaces " Journal of Physics: Condensed Matter, 19, 356003, 2007.
    [20] K A Barnes, A Karim, J F Douglas, A I Nakatani, H Gruell, E J Amis " Suppression of Dewetting in Nanoparticle-Filled Polymer Films" Macromolecules, 33, 4177–85, 2000.
    [21] S. Sharma, M. H. Rafailovich, D. Peiffer,J. Sokolov "Control of Dewetting Dynamics by Adding Nanoparticle Fillers" Nano Letters, 1, 10, 511-514, 2001.
    [22] V. Bliznyuk, B. Ruhstaller, P. J. Brock, U. Scherf, S. A. Carter "Self-Assembled Nanocomposite Polymer Light- Emitting Diodes with Improved Efficiency and Luminance" Admance Materials, vol. 11, 1257-1261, 1999.
    [23] G. A. Buxton, J. Y. Lee, A. C. Balazs "Computer Simulation of Morphologies and Optical Properties of Filled Diblock Copolymers" Macromolecules, vol. 36, 9631-9637, 2003.
    [24] R. S. Krishnan, M. E. Mackay, C. J. Hawker, H. B. Van "Influence of Molecular Architecture on the Dewetting of Thin Polystyrene Films" Langmuir, vol. 21, 5770-5776, 2005.
    [25] G. Lu, L. Li, X. Yang, "Creating a Uniform Distribution of Fullerene C60 Nanorods in a Polymer Matrix and its Photovoltaic Applications" Small, 4, 601-606, 2008.
    [26] Y. S. Sun. S. H. Wang, A. S. T. Chiang, H. F. Hung, M. C. Chen, K. Wood, "Carboxylic Acid-directed Clustering and Dispersion of ZrO2 Nanoparticles in Organic Solvents: A Study by Small-angle X-ray/Neutron Scattering and NMR" Journal of Physical Chemistry C, 2011, ASAP.
    [27] J. H. Xavier, S. Sharma, Y. S. Seo, R. Isseroff,T. Koga, H. White, A. Ulman, K. Shin, S. K. Satija, J. Sokolov, M. H. Rafailovich"Effect of Nanoscopic Fillers on Dewetting Dynamics" Macromolecules, 39, 2972-2980, 2006.
    [28] M. E. Mackay, A. Tuteja, P. M. Duxbury, C. J. Hawker, B. V. Horn, Z. Guan, G. Chen, R. S. Krishnan "General Strategies for Nanoparticle Dispersion" Science, 311, 1740-1743, 2006.
    [29] J. A. Pomposo, R.L. Alaitz, E. Agustin, R. Javier "Key role of entropy in nanoparticle dispersion: polystyrene-nanoparticle/linear-polystyrene nanocomposites as a model system" Physical Chemistry Chemical Physics, 10, 650-651, 2008.
    [30] M. E. Mackay, A. Tuteja, C. J. Hawker, B. V. Horn, "Effect of Ideal, Organic Nanoparticles on the Flow Properties of Linear Polymers: Non-Einstein-like Behavior" Macromolecules, 38, 8000-8011, 2005.
    [31] M. E. Mackay, T. T. Dao, A. Tuteja, D. L. Jo, B. V. Horn, H. C. Kim, C. J. Hawker, "Nanoscale effects leading to non-Einstein-like decrease in viscosity " Nature Materials, 2, 762-766, 2003.
    [32] D. Weng, H. K. Lee, K. Levon, J. Mao, W. A. Scrivens, E. B. Stephens and J. M. Tour, "The influence of Buckminsterfullerenes and their derivatives on polymer properties " European Polymer Journal, 35, 867-878, 1999.
    [33] I. Borukhov, L. Leibler, "Enthalpic Stabilization of Brush-Coated Particles in a Polymer Melt" Macromolecules, 35, 5171-5182, 2002.
    [34] V. Ganesan, V. Pryamtisyn, A. Z. Panagiotopoulos, H. Liu, S. K. Kumar, "Modeling the anisotropic self-assembly of spherical polymer-grafted nanoparticles" The Journal of Chemical Physics, 131, 221102, 2009.
    [35] J. U. Sommer, M. Stamm, "Polymer-nanoparticle films. Entropy and enthalpy at play" Nature Materials, 6, 260-261, 2007.
    [36] P. Akcora,H. Liu, S. K. Kumar, J. Moll, Y. Li, B. C. Benicewicz, L. S. Schadler, D. Acehan, A. Z. Panagiotopoulos, V. Pryamitsyn, V. Ganesan, J. Ilavsky, P. Thiyagarajan, R. H. Colby, J. F. Douglas , "Anisotropic self-assembly of spherical polymer-grafted nanoparticles" Nature Materious, 8, 354-359, 2009.
    [37] S. Jain, S. C. Jana, "Dispersion of nanofillers in high performance polymers using reactive solvents as processing aids" Polymer, 42, 6897-6905, 2001.
    [38] T. Pakula, J. KŁOS, "Interaction of a spherical particle with linear chains. II. Chains end-grafted at the particle surface" Journal of Chemical Physics, 118, 7682-7689, 2003.
    [39] M. K. Corbierre, N. S. Corbierre, M. Sutton, K. Laaziri, R. B. Lennox, "Gold nanoparticle/polymer nanocomposites: dispersion of nanoparticles as a function of capping agent molecular weight and grafting density" Langmuir, 21, 6063-6072, 2005.
    [40] S. Gupta, Q. Zhang, T. Emrick, T. P. Russell, "“Self-Corralling” Nanorods under an Applied Electric Field" Nano Letters, 6, 2066-2069, 2006.
    [41] K. Ohno, Chen Xu , Vincent Ladmiral ,Russell J. Composto, "Dispersion of polymer-grafted magnetic nanoparticles in homopolymers and block copolymers" Polymer, 49, 3568-3577, 2008.
    [42] J. Liu, T. Tanaka, K. Sivula, A. P. Alivisatos, J. M. J. Fréchet, "Employing End-Functional Polythiophene To Control the Morphology of Nanocrystal-Polymer Composites in Hybrid Solar Cells" Journal of Chemical Society, 126, 6550-6551, 2004.
    [43] L. Zan, Z. Liu, J. Zhong, Z. Peng "Organic modification on TiO2 nanoparticles by grafting polymer" Journal of Materials Science, 39, 3261-3264, 2004.
    [44] X. C. Chen, P. F. Green, "Structure of thin film polymer/nanoparticle systems: polystyrene (PS) coated-Au nanoparticle/tetramethyl bisphenol-A polycarbonate mixtures (TMPC)" Soft Matter, 7, 1192-1198, 2011.
    [45] A. S. Robbes, J. Jestin, F. Meneau, F. Dalmas, O. Sandre, J. Perez, F. Bou, F. Cousin, "Homogeneous Dispersion of Magnetic Nanoparticles Aggregates in a PS Nanocomposite: Highly Reproducible Hierarchical Structure Tuned by the Nanoparticles’ Size" Macromolecules, 43, 5785-5796, 2010.
    [46] L. Meli, A. Arceo, P. F. Green, "Control of the entropic interactions and phase behavior of athermal nanoparticle/homopolymer thin film mixtures" Soft Matter, 5, 533-537, 2009.
    [47] L. Meli, A. Arceo, P. F. Green, "Glass transition of polymer-nanocrystal thin film mixtures: role of entropically directed forces on nanocrystal distribution" Nano Letters, 8, 2271-2276, 2008.
    [48] L. Jessica, X. Jia, V. Witherspoon, E. E. Kalu, X. Yang and M. R. Bockstaller, "Effect of Matrix Molecular Weight on the Coarsening Mechanism of Polymer-Grafted Gold Nanocrystals" Langmuir, vol. 26, 12190-12197, 2010.
    [49] Y. Xie, S. Sen, A. Bansal, H. Yang, K. Cho, L.S. Schadler, and S.K. Kumar, "Equivalence between polymer nanocomposites and thin polymer films: Effect of processing conditions and molecular origins of observed behavior " The European Physical Journal - Special Topics, 141, 161-165, 2007.
    [50] M. E. Mackay, R. S. Krishnan, P. M. Duxbury, A. Pastor, C. J. Hawker, B. V. Horn, S. Asokan, M. S. Wong, "Self-Assembled Multilayers of Nanocomponents" Nano Letters, 7, 484-489, 2007.
    [51] T. Emrick, A. C. Balazs, T. P. Russell, "Nanoparticle Polymer Composites: Where Two Small Worlds Meet" Science, 314, 1107-1110, 2006.
    [52] B. J. Kim, J. Bang, C. J. Hawker, E. J. Kramer, "Effect of Areal Chain Density on the Location of Polymer-Modified Gold Nanoparticles in a Block Copolymer Template" Macromolecules, 39, 4108-4114, 2006.
    [53] Russell B. Thompson, Valeriy V. Ginzburg, Mark W. Matsen, Anna C. Balazs "Predicting the Mesophases of Copolymer-Nanoparticle Composites" Science, 292, 2469-2472, 2001.
    [54] 莫志深. 殷敬華, "現代高分子物理學," 科學出版社, p. 934, 2001.
    [55] 陳力俊、張立、梁鉅銘、林文台、楊哲人、鄭晃忠, "材料電子顯微鏡學," 儀器科技研究中心, 1, 1990.
    [56] N. Andrew, "Co-refinement of multiple-contrast neutron/X-ray reflectivity data using MOTOFIT" Journal of Applied Crystallography, 39, 273-276, 2006.
    [57] R. J. Roe, "Methods of X-ray and Neutron scattering in polymer science" Oxford University Press: New York, Chap.5, 155, 2000.
    [58] G. Beaucage, "Approximations Leading to a Unified Exponential /Power-Law Approach to Small-Angle Scattering" J. Appl. Cryst., 28, 717-728, 1995.
    [59] P. Reineker, R.G. Winkler, G. Glatting, "Freely jointed chain with variable segment number and length" Colloid and Polymer Science, 273, 32-37, 1995.
    [60] R. G. Kirste, Makromol. Chem, 101, 91, 1967.
    [61] K. R. Shull, A. M. Mayes, T. P. Russell, "Segment distributions in lamellar diblock copolymers" Macromolecules, 26, 3929-3936, 1993.
    [62] E. H. Immergut, J. Brandrop, E. A. Grulke, Polymer Handbook 4. 1999, VII411
    [63] G. R. Carlow, "Ostwald ripening on surfaces when mass conservation is violated: spatial cluster patterns" Physical A, 239, 65-77, 1997.
    [64] S. Krylov, K. Shorlin, Z. A. Martin "Fundamental problems concerning three dimensional clustering on surfaces " Physical A, 261, 248-265, 1998.
    [65] P. F. Green, L. Meli, "Aggregation and coarsening of ligand-stabilized gold nanoparticles in poly(methyl methacrylate) thin films" ACS Nano, 2, 1305-1312, 2008.
    [66] R. Kofman, E. Sondergfird , P. Cheyssac, A. Stella, "Production of nanostructures by self-organization of liquid Volmer-Weber films" Surface Science, 364, 467-476, 1996.
    [67] K. Fuchs, Chr. Friedrich, J. Weese "Viscoelastic Properties of Narrow-Distribution Poly(methyl methacrylates)" Macromolecules, 29, 3-5901, 1996.
    [68] E. Sivaniah, J. Heier, E. J. Kramer, "Anisotropic coarsening of two-dimensional surface domainin copolymer thin films" Macromolecules, 32, 9007-9012, 1999.
    [69] P. F. Green, R. Limary, "Late-stage coarsening of an unstable structured liwuid film" Physical Review E, 66, 021601, 2002.
    [70] Jenny Kim, Peter F. Green "Directed Assembly of Nanoparticles in Block Copolymer Thin Films: Role of Defects" Macromolecules, 43, 10452-10456, 2010.
    [71] P. F. Sheridan, D. B. Adolf, A. V. Lyulin, I. Neelov, G. R. Davies "Computer simulations of hyperbranched polymers: The influence of the Wiener index on the intrinsic viscosity and radius of gyration" J Chem. Phys., 117, 7802-7812, 2002.

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