側鏈/超分子型高分子材料於光電領域之應用

Abstract

近年以來，受益於活性/可控聚合方法的蓬勃發展，科學家發展出許多不同的高分子結構。為了加速高分子領域的發展進程，設計出在特定高分子骨架上可改質不同官能基的側鏈型高分子是相當重要的課題。另一方面，受到自然界的啟發，超分子化學的觀念在近幾年對於高分子科學的分子設計有著相當程度的影響，間接帶起了許多有關側鏈接枝型高分子的研究。值得一提的是，科學家發現運用非共價作用力所形成的聚合物或複合材料能夠有效的提高材料本身的性質。因此，如何快速優化這些特別的材料並建立適用的研究方法成為了許多跨領域的研究者所追逐的目標。 本論文旨在藉由簡易的官能基修飾建立適用於不同種類官能化側鏈/超分子型高分子材料的設計、合成與分析方法。研究將著重在固態及溶液態中材料本身的性質提昇與應用探討︰

(1) 刺激響應超分子材料之光可調控性與分子識別探討 在本研究中我們成功的將二氨基吡啶 (DAP)官能基藉由點擊化學導入到利用氮氧自由基調控聚合而得的聚苯乙烯側鏈。此高分子材料PVB-DAP能夠與含有胸腺嘧啶(Thymine)的偶氮苯小分子配對形成複合材料，並展現特別的光響應特性。在適當波長的UV光照射下可以觀察到材料的順反異構化行為，並帶給薄膜表面親疏水性質的轉換。此外，我們發現此超分子系統所特有的非共價偶氮苯結構能夠用來製備表面光柵，其可重複讀寫的特性也為光學儲存元件提供了新的材料選擇。

(2) 運用π-π及強氫鍵作用力所製備之超分子型聚胜肽材料及其於碳管分散之探討 新型超分子聚胜肽可由簡單的開環聚合反應(ROP)與點擊化學製備而得。分析結果顯示導入超分子官能基可促進α-螺旋二級結構的形成，並額外提昇熱性質與熱響應性。此外，結合互補小分子Py-T我們製備了聚胜肽/芘複合材料並探討其性質。由材料所提供的非共價作用力除能穩定超分子系統的結構外，也可用於碳管分散。藉由超分子系統的輔助，單壁及多壁奈米碳管可分散在極性或非極性的溶劑中，降低了碳管複合生醫材料的製備難度。

(3) 帶有疊氮基團之抗溶劑腐蝕型電洞傳輸/注入共軛高分子於螢光及磷光OLED元件之製備 在本研究中，我們藉由鈴木耦合反應合成了側鏈官能化之共軛高分子PTCAz。在UV光的照射下此材料可形成穩定之交聯結構，並提供良好的抗溶劑腐蝕性及電化學穩定性。結合主鏈結構上的芳香胺基團所擁有良好的電洞傳輸能力，我們預期PTCAz適合作為OLED元件的電洞/注入傳輸材料。基於此材料所製作的Alq3螢光元件最大亮度(Bmax)為52971 cd/m2，發光效率(LE)與能源轉換效率(ηE)皆高於市售電洞傳輸材料PEDOT:PSS元件的表現。此外，我們發現此材料交聯後能夠避免濕式元件製程中常遇到的介面互溶問題，因此製作了濕式磷光元件，其效能表現為:[外部量子效率(EQE): 7.93%; LE: 29.6 cd/A; ηE: 14.3 lm/W; Bmax: 34,484 cd/m2] 此材料之製程簡單，且在交聯的過程中無需添加任何試劑，適合用於高效能低成本之OLED元件製作。

(4) 互補型多點氫鍵超分子應用於水溶性螢光奈米粒子的製備 基於上述研究，我們進一步將共軛高分子材料PTCAz結合多點式氫鍵官能基合成為共軛超分子材料。在此研究中，我們選用DNA含氮鹼基對腺嘌呤Adenine (A)、胸腺嘧啶Thymine (T)來進行分子識別的研究。均聚物PC-T及共聚物PTC-T皆擁有相當高的玻璃轉移溫度(Tg)，且在質子型與非質子型溶劑顯示出不同的發光行為。藉由A-T鹼基對所提供的多點氫鍵作用力，能夠使疏水的共軛高分子形成水溶性的微胞結構，並利用其發光特性來製備螢光奈米粒子。結果顯示運用非共價作用力所形成的PC-T/PEG-A及PTC-T/PEG-A粒子具有良好的生物相容性與高訊雜比，證實超分子化學對於分子設計與材料應用具有相當大的潛力。

In the recent past, living/controlled polymerization techniques have enabled the preparation of a large variety of distinct well defined co(polymer) architectures. To accelerate the research progress of novel polymers, it would be highly desirable to design a general polymer backbone with variable side-chain functionalities in order to tune the properties of the resulting (co)polymers. In the last decade, the use of supramolecular chemistry towards the synthesis of side-chain functionalized polymers has developed from a curiosity to a mature area of polymer science. Furthermore, it has to be demonstrated that polymers or complexes functionalized using non-covalent methodologies indeed possess advantages superior than their covalent counterparts. ‘Rapid optimization’ of these advanced materials and establishment of the methodology are actively pursued in a broad range of research fields. This thesis involves the design principles, syntheses, and methodologies of various functional side-chain/supramolecular polymeric materials via post-functionalization methods. Properties enhancement and potential applications are presented in both solid state and solution state:

(1) Stimuli-Responsive Supramolecular Materials: Photo-Tunable Properties and Molecular Recognition Behavior A successfully introduction of multiple hydrogen bonding unit diaminopyridine (DAP) into a conventional polymer polystyrene (PS) utilizing nitroxide-mediated polymerization and CuAAC “click” technique have been proposed in this study. Complexation of this PVB-DAP polymer and thymine-functionalized azobenzene (Azo-T) through directional complementary triple hydrogen bonding interaction has led to a special photoresponsive behavior. A reversible trans-cis isomerization process can be observed upon UV light illumination and thus resulted in a change of surface properties. During isomerization, a hydrophobic-to-hydrophilic surface of supramolecular thin film according to water contact angle (WCA) measurements can be achieved with several repeated cycles. Furthermore, it was found that PVB-DAP/Azo-T supramolecular complex film have ability to form surface-relief grating from the interference pattern of polarized green light (532 nm) laser. The “recordability” and “rewritability” of these supramolecular complexes provides a unique strategy to perform stimuli-responsive materials for optical storage application.

(2) Functional Supramolecular Polypeptides Involving π-π Stacking and Strong Hydrogen Bonding Interactions: A Conformation Study Toward Carbon Nanotubes (CNTs) Dispersion Novel supramolecular polypeptides were prepared through facile syntheses including ring opening polymerization (ROP) and "click" reaction. Supramolecular polypeptides PPLG-DAPs have been proven to enhance the α-helical secondary structures of PPLGs. An obvious increase of thermal properties and thermal responsivity has been provided by dynamic physical-crosslinking network of DAP-DAP self-assembly interaction. On the other hand, molecular recognition process has been carried out between DAP and thymine base pairs to form the peptide/pyrene supramolecular complex. TEM results suggest the supramolecular complex PPLG-DAP/Py-T can be used as an efficient carbon nanotube (CNT) dispersant in both polar and non-polar media via the combination of secondary interactions including multiple hydrogen bonding and π-π interaction. PPLG-DAP/Py-T/MWCNT composite with high Tg value thus enable the development of bioinspired carbon nanostructures and lead the way toward biomedical applications.

(3) A Solvent-Resistant Azide-Based Hole Injection/Transporting Conjugated Polymer for Fluorescent and Phosphorescent Light-Emitting Diodes Side-chain functionalized conjugated polymer PTCAz has been synthesized for a precursor polymer through Suzuki-coupling method. The readily photo-crosslinkable unit and sufficient hole transporting ability made PTCAz a suitable material to fabricate hole injection/transporting layer (HITL) of solution-processed OLEDs. With the excellent solvent-resistance and remarkable electrochemical stability, PTCAz have offered an extra option to solve the interfacial mixing problem which generally decrease the efficiency of solution-processed OLEDs. As a result, the Alq3-based trilayer fluorescent device reached a maximum brightness of 52971 cd/m2, maximum luminance efficiency (LE) and power efficiency (ηE) are both higher than those of a corresponding device based on commercial PEDOT:PSS. In addition, a solution-processed phosphorescent OLED device incorporating X-PTCAzide also exhibited good performance (external quantum efficiency: 7.93%; LE: 29.6 cd/A; ηE: 14.3 lm/W; maximum brightness: 34,484 cd/m2). The efficient and simple photo-crosslinking without adding initiator could make PTCAzide a promising next-generation HITM for the development of highly efficient and inexpensive OLEDs.

(4) Water-Soluble Fluorescent Nanoparticle Fabrication Based on Supramolecular Amphiphiles via Heterocomplementary Multiple Hydrogen Bonding Interactions Water-dispersible luminescent polymer dots with absence of ionic groups and simple preparation process are desired for their versatile applications especially in biological imaging. In this study, we proposed a facile strategy to fabricate Water-dispersible polymer dots through bio-inspired non-covalent molecular recognition process. The side-chain type supramolecular conjugated polymers, PC-T and PTC-T, were obtained from a brief modification of previously reported azide-functionalized polymers. Such hydrogen-bonded materials demonstrated distinct luminescent properties in protic and aprotic solvents while exhibited improved thermal properties and stabilities and more importantly, provided an extra pairing ability to other complementary base units. Supramolecular micelle can be therefore prepared from conjugated polymers and complementary hydrophilic polymer PEG-A. The resulting PC-T/PEG-A and PTC-T/PEG-A micelles exhibited at the scale of hundred nanometers and were able to act as “polymer dots” for in vitro experiments. The prescence of PEG shells created biomimetic surfaces that sustained the biocompatibilty for practical usage. Our attempt indicated the supramolecular system involved specific nucleus bases recognition may be a reliable process to apply hydrophobic polymers into modern biological analysis.