側鏈含共軛寡聚物之醣類嵌段共聚高分子之合成、形態與電子元件應用

Synthesis, Morphology and Electrical Device Applications of Oligosaccharide-based Block Copolymers with Pendent Conjugated Moieties

孫翰笙(Han-Sheng Sun)

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(2016年)

https://doi.org/10.6342/NTU201603655

摘要

可再生高分子具有環境永續性、可生物降解性與蘊含量充沛等特點，被視為取代石化高分子的最佳選擇，引起了高度的研究興趣。於此論文中，結合天然寡醣，合成出一系列側鏈含共軛寡聚物之醣類嵌段共聚高分子並探討其自組裝行為與用於電晶體式記憶體之元件表現。此外，利用此醣類嵌段共聚高分子所形成之超分子電荷儲存層亦被用於開發非揮發性電晶體式記憶體元件。本論文之研究重點茲分述如下：
本論文第一部分(第二章)-藉由活性陰離子聚合法、疊氮化反應與一價銅催化點擊反應，側鏈含不同共軛長度芴(fluorene)寡聚物之醣類嵌段共聚高分子成功的被製備。此醣類嵌段共聚高分子經由退火處理可以自組裝形成次10奈米的球狀微結構。進一步將其做為電晶體式記憶體元件之電荷儲存層，所有的記憶體元件皆展現優良的載子遷移率(0.25-0.52 cm2 V-1 s-1)、良好的記憶特性、高的開關電流比(107-108)與104秒以上的記憶儲存時間。全部元件中，麥芽七醣-側鏈單芴嵌段共聚高分子(MH-b-PStFl1)元件的操作穩定性能達到至少180次。研究發現，側鏈雙芴高分子(PStFl2)與側鏈單芴高分子(PStFl1)相比具有較大的分子扭轉角度，阻礙了五環素(pentacene)半導體層的分子排列，進而導致較差的載子遷移率。此外，引入醣類嵌段能有效增加電子捕捉效果，提升記憶窗口。而側鏈雙芴高分子(PStFl2)有較高的最高佔據分子軌域，能讓較多的電荷轉移至此儲存，因此擁有較大的記憶窗口。
本論文第二部分(第三章)-利用有機磷腈鹼(t-Bu-P4)催化基團轉移聚合法、一價銅催化點擊反應與分子氫鍵作用力，側鏈含芘(pyrene)寡聚物之醣類嵌段共聚高分子與其超分子(supramolecules)可以成功的被製備。藉由調控嵌段比與熱退火過程，此嵌段共聚高分子能自組裝成次10奈米的柱狀及球狀結構。相反的，上述高分子與其超分子薄膜，只能形成球狀的奈米結構。將超分子薄膜當成電荷捕捉層製備電晶體式記憶體，元件具有優異的載子遷移率(0.20-1.08 cm2 V-1 s-1)、良好的開關電流比(107-108)、長時間記憶特性(大於104 s)與100次以上的可重複操作性。研究顯示，五環素(pentacene)於苯并噻二唑(BT)超分子駐體表面形成較規整的結晶結構，因此苯并噻二唑(BT)元件相較於異靛藍(isoindigo)元件表現出較高的載子遷移率。此外，記憶窗口可以藉由摻混的電子受體小分子與側鏈芘(pyrene)寡聚物之比例加以調控，最大可達34 V。
上述研究顯示出自組裝結構尺寸與記憶體元件特性能藉由引入天然高分子嵌段加以控制，同時展露了天然材料於非揮發性電晶體式記憶體應用上之潛力。

關鍵字

嵌段共聚高分子 ； 自組裝 ； 超分子 ； 高分子駐體 ； 綠色元件

並列摘要

Renewable polymers have attracted extensive research interest in the past decade, because they are environmentally sustainable, biodegradable and inexhaustible sources with the production of 1013 tons annually, which have been regarded as a promising candidate for substituting the petroleum-based materials. In this thesis, we report the synthesis, morphology, and organic memory application of the oligosaccharide-based diblock copolymers with pendent -conjugated moieties and their supramolecules with modified electron-accepting small molecules for the nonvolatile transistor memory devices were investigated as well. The following summarize the important discovery of this thesis:
1. Synthesis of Oligosaccharide-Based Block Copolymers with Pendent π-Conjugated Oligofluorene Moieties and Their Electrical Device Applications (Chapter 2): Oligosaccharide-based diblock copolymers consisting of a maltoheptaose (MH) block and a poly(4-oligofluorenylstyrene) block (PStFln, n = 1 or 2), referred to as MH-b-PStFln was prepared by the Cu(I)-catalyzed click reaction of ethynyl-modified MH and azido-terminated PStFln. The resulting diblock copolymers self-assembled to spherical microdomains with sub-10 nm sizes in both bulk and thin film state after annealing process. Thereafter, the MH-b-PStFln thin film (~50 nm) with the self-assembled nanoscale spherical aggregates was used as the charge storage layer for the pentacene-based field-effect transistor type memory devices. The MH-b-PStFln-based devices had the excellent hole mobility (0.25-0.52 cm2 V-1 s-1) and the high ON/OFF current (ION/IOFF) ratio of 107-108, of which the MH-b-PStFl1-based one had the higher mobility than that of the MH-b-PStFl2-based one because the pentacene crystals in the former device possessed the larger grain size and fewer boundaries. On the other hand, the MH-b-PStFl2-based device showed a larger memory window than the MH-b-PStFl1-based one because the stronger donating effect of the difluorenyl group in MH-b-PStFl2 increased the charge storage capability of its related device. All the memory devices showed a long-term retention time over 104 s with the high ION/IOFF ratio of 106-108. Among these devices, the MH-b-PStFl1-based device showed a good WRER endurance over 180 cycles.
2. Synthesis, Morphology, and Electrical Memory Application of Oligosaccharide-Based Block Copolymers with π-Conjugated Pyrene Moiety and Their Supramolecules (Chapter 3): Maltoheptaose-block-poly(1-pyrenylmethyl methacrylate) (MH-b-PPyMA) was prepared by the combination of the t-Bu-P4-catalyzed group transfer polymerization and the Cu(I)-catalyzed azide-alkyne cycloaddition reaction, and then formed supramolecules with (4-pyridyl)-acceptor-(4-pyridyl), MH(4Py-Acceptor-4Py)x-b-PPyMA. After thermal annealing process, the MH-b-PPyMA bulk sample underwent microphase separation to form the sub-10 nm periodic self-assembled nanostructure. The self-assembled morphologies transform from the hexagonally cylindrical packing to the body-centered cubic spherical arrangement and disorderly spherical nanodomain by increasing the PPyMA segment length. On the contrary, only spherical nanodomain was observed in the thermo-annealed thin film samples of both MH-b-PPyMA and MH(4Py-Acceptor-4Py)x-b-PPyMA. The electrical characteristics of the p-type pentacene-based OFET memory device using the thermo-annealed polymer thin film as the electret layer was studied. The MH(4Py-Acceptor-4Py)x-b-PPyMA-based organic field effect transistor (OFET) devices had the high hole mobility of 0.20-1.08 cm2 V-1 s-1 and the ON/OFF current (ION/IOFF) ratio of 107-108, in which the acceptor of benzo[c][1,2,5]thiadiazole (BT) based device possessed the higher hole mobility than that of isoindigo-based one due to the more ordered packing pentacene crystals. The memory window (ΔVTH) of the supramolecule-based device was increased with enhancing the 4Py-Acceptor-4Py blending composition, and that of MH(4Py-BT-4Py)1.5-b-PPyMA10-based device had the largest ΔVTH of ca. 34 V, a long-term retention time greater than 104 s and the high ION/IOFF memory ratio of 106-107 (reading at Vg = 0 V) for more than 100 programming/erasing cycles.
The above studies demonstrate that the size of self-assembled morphologies and memory characteristics can be manipulated by incorporation of hydrophilic natural polymer blocks and the potential of the natural materials for nonvolatile flash memory applications.

並列關鍵字

block copolymer ； self-assembly ； supramolecule ； polymer electrets ； green electronics

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