Molecular Packing in Crystalline Polyfluorenes｜國立清華大學博碩士論文庫

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研究生：	黃聖恩 Huang, Sheng-En
論文名稱：	Molecular Packing in Crystalline Polyfluorenes
指導教授：	蘇安仲 An-Chung Su
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 化學工程學系 Department of Chemical Engineering
論文出版年：	2009
畢業學年度：	97
語文別：	英文
論文頁數：	43
中文關鍵詞：	分子堆積、PFO 、PFH 、α形式
外文關鍵詞：	molecular packing, PFO, PFH, αform
相關次數：	點閱：34 下載：0
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本論文主要是研究poly(9,9-di-n-oxtyl-2,7-fluorene) (PFO)和poly(9,9-di-n-hexyl-2,7- fluorene) (PFH)的主鏈構形、分子堆疊和其光激發、放光之間的關聯。就主鏈構形而言，量子力學計算(Gaussian 03)之結果顯示: (1) PF系列主鏈之能隙隨單體之180度翻轉會略有差異，亦即簡單之C2對稱並不完全適用；(2) 相鄰單體偏離共平面約狰140o時為α相的最低能量單鏈構形。依此單鏈構形為基礎，我們的分子力學計算(Accelrys Cerius2)獲得與PFO及PFH之電子擇區繞射實驗圖案極為符合之計算結果，顯示PFO之α晶相為bi-radial II形式的側鏈構形而PFH之α晶相則為bi-radial I形式的側鏈構形，後者環抱相鄰主鏈的傾向較高。

Here we report results of our study of chain conformation, molecular packing, and corresponding effects on photo-excitation and luminescence behavior of poly(9,9-di-n-oxtyl-2,7- fluorene) (PFO) and poly(9,9-di-n-hexyl-2,7-fluorene) (PFH) using quantum mechanical (QM, Gaussian 03) and molecular mechanics (MM, Accelrys Cerius2) calculations. We demonstrate that the single-chain excitation energy can be slightly different upon pi-flipping of a fluorene monomer; this signifies difference between the two most likely (i.e., UDUD vs. DDUU) candidates for backbone conformation in the crystalline state. Excluding the DDUU conformation based on monomer length from MM, its tendency to bend from QM calculation, and symmetry requirement from crystallographic argument, we adopt UDUD conformation with alternating fluorene torsion angles of +_140 as the single chain conformation and proceed with MM simulation of chain packing in the α phase of PFO and PFH. Results agree well with experimental zone patterns from selected-area electron diffraction and indicate that the n-hexyl side-chains of PFH tend to take bi-radial I conformation whereas the octyl side-chains of PFO tend to take bi-radial II conformation. Due to differences in the preferred conformation, side-chains in PFH show stronger tendency to embrace a neighboring backbone than those in PFO.

摘要    III
Abstract    IV
Table of Contents    V
List of Figures    VI
1. Background    1
1-1. Introduction    1
1-1.1. Phase Behavior and Molecular Packing of Poly(9,9-di-n-oxtyl-2,7-fluorene)    1
1-1.2. Phase Behavior and Molecular Packing of Poly(9,9-di-n-hexyl-2,7-fluorene)    2
1-2. Unresolved Issues    2
1-3. Objectives and Approaches    3
2. Simulation & Crystallographic Details    4
2-1. Gaussian 03    4
2-1.1. Ground State Molecular Structure    4
2-1.2. Excited State Molecular Structure    5
2-1.3. Excitation Energy    5
2-2. Accelrys Cerius2    6
2-2.1. Force Field    6
2-2.2. Basic Principle for Energy Minimization    6
2-2.3. Procedures in Performing Molecular Simulation    7
3. Molecular Packing in Crystalline Polyfluorenes    9
3-1. Single Chain Conformation Study    9
3-1.1 Backbone Structure    9
3-1.2 Side-chain Conformation    10
3-1.3 The Molecular Packing of PFO with No Side-chain    10
3-1.4 The Side-chain Effect in Molecular Packing of PFO    11
3-2. Molecular Packing in Crystalline PFH    12
4. Conclusion    13
5. References    14
Appendix    26

                                

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