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研究生：	曾冠霖 Tseng, Kuan-Lin
論文名稱：	側鏈長度對聚芴分子於亞共晶二元系中聚集排列行為之影響 Sequential Epitaxial Organization of Polyfluorenes in Hypo-Eutectic Mixture under the Impact of Side Chain Length
指導教授：	阮至正 Ruan, Jr-jeng
學位類別：	碩士 Master
系所名稱：	工學院 - 材料科學及工程學系 Department of Materials Science and Engineering
論文出版年：	2013
畢業學年度：	101
語文別：	英文
論文頁數：	67
中文關鍵詞：	聚芴、共晶系統、側鏈
外文關鍵詞：	polyfluorene, epitaxial organization, eutectic system, side chain
相關次數：	點閱：67 下載：1
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本研究中探討高分子Poly(9,9-di-n-octyl-2,7-fluorene)(PFO)與小分子Hexamethylbenzene (HMB)均勻混和的共晶系統，並以此基礎研究系統的相變態行為。此研究發現，由於HMB在熔融狀態的溶劑效應，PFO的nematic液晶相會同時呈現液向性(lyotropic)以及熱向性(thermotropic)。冷卻過程中，HMB溶劑會先結晶析出，誘發PFO以新的液晶相smectic相析出。X光繞射和擇區電子繞射進一步指出，face-on的有序排列以及沿著側鏈的層狀堆疊。
在高溫退火處理下，發現HMB結晶促使PFO smectic相轉變為更穩定的β晶相。smectic相和β晶相有共同的紫外光吸收特徵峰，而其螢光光譜均有紅位移的現象(相較於α晶相)，反應出較小的能帶間隙。推論HMB基材可以穩定PFO主鏈的共平面性，造成能帶間隙變小。在退火處理時，若沒有HMB結晶的存在，則smectic相會轉變為α晶相。在高溫退火的熱擾動，會導致PFO 主鏈的扭曲，因此發展出來的分子鏈段排列為α晶相的結構。而主鏈的扭曲與共平面性的減少，會使能帶間隙增加，於是觀察到較短的螢光波長。
研究中發現，另一聚芴衍生物Poly(9,9-di-n-hexyl-2,7-fluorene)(PFH)與HMB亦能均勻混和而形成共晶系統。HMB結晶亦可誘發PFH β晶相的生成。由X光繞射和擇區電子繞射的結果推論，PFH是沿著π-π鍵結方向堆疊形成edge-on板晶。這個結果指出，當側鏈較短時，分子鏈段會傾向以側鏈和HMB基材接觸，主鏈的共軛平面則垂直於基材。
在高溫退火時，若沒有HMB結晶的存在，β晶相進一步轉變為α相。吸收光譜α和β晶相很相似，但是在激發光譜中，β晶相有一紅位移。進一步確認HMB結晶基材穩定了β相主鏈的共平面性。

The binary eutectic system of poly(9,9-di-n-octyl-2,7-fluorene) (PFO) and hexamethylbenzene (HMB) has been established. Molten HMB plays a role of solvent, which causes the PFO nematic phase in binary mixtures to exhibit both lyotropic and thermotropic features. Cooling from the molten state, the growth of PFO smectic phase is epitaxially induced on HMB crystal. This smectic packing is featured with face-on organization of PFO backbones, and layer stacking of side chains. Upon the annealing with the presence of HMB crystals, further organization of PFO smectic phase on HMB crystals results in the crystalline packing of β phase. Whereas, without HMB crystals, the annealing treatment makes the smectic phase transform to α crystalline phase. Both smectic and β phases of PFO yield characteristic ultraviolet (UV) absorption at 434 nm wavelength and photoluminescence at the wavelength of 441 nm. The UV absorption and fluorescence of α form is at relatively shorter wavelengths. Concerning the molecular packing within the smectic phase and β phase, the observed red shift of UV absorption and fluorescence reflects lower energy bandgap and enhanced backbone planarity by epitaxial effect.
The eutectic system of poly(9,9-di-n-hexyl-2,7-fluorene) (PFH) and hexamethylbenzene (HMB) have also been studied. During cooling from molten state, the growth of PFH β phase is epitaxially induced on HMB crystals. Different from the face-on packing of PFO backbone, the organization of PFH backbone adopt the edge-on orientation based on the interaction between side chains and HMB substrate. Upon the annealing treatment without HMB crystals, the β phase transforms to α phase. The UV absorption spectrums of α phase and β phase are similar. Nevertheless, for the photoluminescence of β phase, the red shift was observed as being compared to the PL spectrum of α phase. Therefore, with the prevalence of edge-on organization of PFH molecular stems on crystalline substrate, backbone planarity can be enhanced still via involved epitaxial relationship.

摘要 I
Abstract II
誌謝 IV
List of Tables VIII
List of Figures IX
Chapter I. Introduction 1
I-1 Background 1
I-2 Principle of Photoluminescence 2
I-3 Motivation 5
Chapter II. Literature study 6
II-1 Introduction 6
II-2 Poly(9,9-di-n-octyl-2,7-fluorene) 7
II-2-1 Crystalline Forms and Phase Behavior of Poly(9,9-di-n-octyl-2,7-fluorene) 7
II-2-2 Photophysics of Poly(9,9-di-n-octyl-2,7-fluorene)15
II-3 Poly(9,9-di-n-hexyl-2,7-fluorene) 18
II-4 Epitaxial Crystallization 22
II-5 Epitaxial Crystallization of Polyfluorene 24
Chapter III. Experimental Details 27
III-1 Material 27
III-2 Instruments used 29
III-3 Experimental procedures 32
III-3-1 In-situ POM observation 32
III-3-2 TEM sample preparation 32
III-3-3 UV. PL sample preparation 32
III-3-4 DSC. X-ray sample preparation 33
Chapter IV. Results and Discussion 34
IV-1 Binary mixtures of poly(9,9-di-n-octyl-2,7-fluorene) (PFO) and hexamethylbenzene (HMB) 34
IV-1-1 Solvent effect of hexamethylbenzene on poly(9,9-di-n-octyl-2,7-fluorene) 34
IV-1-2 Establishment of phase diagram via measuring phase stabilities 35
IV-1-3 Identification of the additional lyotropic feature of nematic phase 40
IV-1-4 Epitaxial Organization upon Cooling 42
IV-1-5 Phase Transformation Route of Smectic Phase upon Annealing 46
IV-2 Binary mixtures of poly(9,9-di-n-hexyl-2,7-fluorene)
(PFH) and hexamethylbenzene (HMB) 52
IV-2-1 Solvent effect of hexamethylbenzene on poly(9,9-di-n-hexyl-2,7-fluorene) 52
IV-2-2 Epitaxial Organization upon Cooling 56
IV-2-3 Phase Transformation upon Annealing 60
Conclusion 63
References 65
                                    

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校內：2018-08-27公開
校外：2018-08-27公開

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