多功能芴系共聚物高分子:合成、形態與光物理性質之研究

Multifunctional Fluorene Based Copolymers: Synthesis, Morphology and Photophysical Properties

邱昱誠(Yu-Cheng Chiu)

指導教授 ： 陳文章

國立臺灣大學/工學院/化學工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.00291

摘要

環境應答型共聚高分子對環境中特定標的物之靈敏度而受到廣泛應用。特別是環境應答型高分子共聚共軛高分子材料，因其具有螢光或電氣性質，可隨環境微小變異有效操控材料之光電性質而受到矚目。多數含共軛硬桿感測高分子之研究文獻仍著重於溶液或薄膜型態，即使奈米纖維具有大比表面積之特性可提升感測效率，卻相對地較少被研究於感測領域。在本論文研究中，設計一系列多功能芴系共聚高分子，開發具大比表面積的多功能性奈米感測纖維與多孔性材料於感測領域之應用，此外，含芴系高分子亦可應用於電晶體型記憶體之介電層。
在此論文第二章，製備多功能溫度應答型含側鏈芴系無規共聚高分子poly((2-(dimethylamino)ethylmethacrylate)-co-(stearylacrylate)-co-(9,9-dihexyl-2- (4-vinylpenyl)-9H-fluorene)) (Poly(DMAEMA -co-SA-co-StFl))，各個單體分別具有溫度應答、物理交聯與螢光特性。藉由fluorene 與SA鏈段調控P4高分子之低臨界溶液溫度於32.5℃，使之靜電紡絲纖維具有溫度感應之纖維體積澎潤與收縮之特性。由於PDMAEMA鏈段隨升溫與降溫產生高分子鏈延展與收縮之特性，帶動溫度變化所形成之纖維型態與螢光強度皆具可逆性，呈現環境應答之開/關特性，可當作一良好環境感測器材料。
於第三章，研究含主鏈芴系之共軛硬桿-柔軟-柔軟三嵌段高分子(PF-b-PNIPAAm-b-PNMA)之合成、型態與應用。PF、PNIPAAm與PNMA各嵌段分別具有螢光、親水溫度感應與化學交聯之功能性，進而運用單軸靜電紡絲技術將高分子水溶液製備成多功能電紡纖維。藉由SAXS與TEM鑑定纖維內部奈米微結構為沿著軸向規整之層狀排列 (Lamellar structure)。交聯後的PF-b-PNIPAAm-b-PNMA靜電紡絲奈米纖維在水中可保持其纖維型態及良好透濕性，展現具溫度感應開關及可回復的螢光特性。
論文的第四章，成功合成共軛硬桿與結晶軟鏈雙嵌段poly[2,7-(9,9-dihexylfluorene)]-block-poly(stearyl acrylate) (PF-b-PSA)高分子。軟鏈端為含十八個長碳鏈之結晶性高分子PSA (crystalline comb-like PSA)，在Breath Figure成膜過程中，有效地沉降並藉由PF穩定水珠於高分子上的排列，獲得高度規整排列之中孔洞材料。隨著軟鏈嵌段增長、環境濕度與高分子溶液濃度增加有助於孔洞規整性。藉由掃描式電子顯微鏡與掃描式雷射共焦顯微鏡鑑定，均勻呈現藍色螢光且完美地單層排列。再者，將其表層去除可獲得高比表面積之rod-co-valley-like結構，並具有超疏水之特性。
在此論文第五章，成功利用線性與星狀之P(St-Fl)作為pentacene-based有機電晶體型記憶體之介電層並探討其電氣性質。電場誘發之電荷可儲存於高分子電荷儲存層，因此當正負不同偏壓操作時，此元件顯示較大及可逆的閾值電壓(threshold voltage)。儲存電荷程度與P(St-Fl)高分子介電層之構型有關，並證實運用P(St-Fl)為介電層可提升整體電流開關比、在高低導電態可維持104秒。多次重覆讀寫循環操作可達兩百次以上。
整體研究指出含芴系多功能共聚高分子所製備之靜電紡絲奈米纖維或多孔性薄膜具有潛力應用於感測元件。此外，星狀芴系高分子應用於有機電晶體記憶體介電層展現良好記憶體表現，具有潛力應用於可饒式電子元件。

關鍵字

多功能高分子 ； 靜電紡絲 ； 多孔洞膜 ； 光激發光 ； 電晶體型記憶體

並列摘要

Stimuli responsive copolymers can provide a variety of applications due to their high sensitivity in detecting targeted species. Among of these studies, environmental-responsive polymers containing conjugated segments have attracted considerable attention because their electronic and optoelectronic properties could be efficiently manipulated by minor perturbations of environmental stimuli. However, most studies on responsive copolymers focused on the phases of solution or thin film. Nanofibers of the environmental responsive polymers have not been fully explored yet, although the characteristics of high surface-to-volume ratio could lead to highly efficient sensory devices. In this thesis, we explore the synthesis of fluorene segment containing stimuli-responsive copolymers and their electrospun nanofibers or microporous films for multifunctional sensory applications. Besides, the fluorene-based polymers also were applied on transistor-type memory as electrets.
In chapter 2, thermo-responsive electrospun (ES) fibers prepared from multifunctional random copolymers of poly((2-(dimethylamino)ethyl methacrylate)-co-(stearyl acrylate)-co-(9,9-dihexyl-2-(4-vinylpenyl)-9H-fluorene)) (poly(DMAEMA-co-SA-co-StFl)) were explored. The moieties of DMAEMA, SA, and StFl were designed to exhibit the thermo-responsive, physical corsslinking, and fluorescent functionality, respectively. The prepared P4 copolymer with the DMAEMA/SA/StFl mole ratio of 92/3/5 showed the lower critical solution temperature (LCST) of 32.5 ℃. A significant temperature-dependent swelling and de-swelling behavior was found in the P4 ES fibers, and showed 5-10 nm StFl aggregated domain. Accompanied with volume-changing on the P4 ES fibers, a reversible photoluminescence (PL) was also observed during the heating and cooling cycle, resulted from the extended/compact structural transformation on the PDMAEMA moiety.
In chapter 3, the synthesis, morphology, and applications of conjugated rod-coil-coil triblock copolymers, polyfluorene-block-poly(N- isopropylacrylamide)-block-poly(N-methylolacrylamide) (PF-b-PNIPAAm-b-PNMA) were explored. The blocks of PF, PNIPAAm, and PNMA were designed for fluorescent probing, hydrophilic thermo-responsive and chemically crosslinking, respectively. Electrospun (ES) nanofibers of PF-b-PNIPAAm-b-PNMA were prepared in pure water using a single-capillary spinneret. The SAXS and TEM results suggested the lamellar structure of the PF-b-PNIPAAm-b-PNMA along the fiber axis. These obtained nanofibers showed outstanding wettability and dimension stability in the aqueous solution, and resulted in a reversible on/off transition on photoluminescence as the temperatures varied.
In chapter 4, crystalline conjugated rod-coil diblock copolymers of poly[2,7-(9,9-dihexylfluorene)]-block-poly(stearyl acrylate) (PF-b-PSA) were successfully synthesized. The crystalline comb-like PSA coil segment effectively formed the highly ordered microporous films through “breath figure” (BF) process. The longer PSA block length, larger humidity, and higher copolymer concentration formed a more regular PF-b-PSA microporous structure. The images of SEM and scanning laser confocal microscope of the PF7-b-PSA166 microporous film showed that all bubbles were independent and perfectly monodisperse with a pore diameter ca. 1.85 μm. Furthermore, a rod-co-valley-like structure can be achieved and exhibited a superhydrophobicity.
In chapter 5, we demonstrated the controllable electrical switching behavior of the pentacene-based OFET memory using linear and star-shaped P(St-Fl) as electrets. The large and reversible threshold voltage shift in transfer curves suggested that the electronic charges were transferred between P(St-Fl) gate electret and pentacene active layer. The memory windows of the pentacene-based OTFTs were related to the polymer architecture and exhibited high ON/OFF ratio, which could be retained over 104 s. The write-read-erase-read (WRER) cycles could maintain over 200 cycles.
The above studies address the electrospun nanofibers or microporous films prepared from fluorene containing multifunctional copolymers could have potential applications for sensory devices. Besides, star-shaped polymer electrets containing fluorene exhibited excellent OFET memory performance, indicating their potential applications for flexible electronics.

並列關鍵字

multifunctional copolymers ； electrospinning ； microoporous ； photoluminescence ； OFET memory

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