芴系硬桿-柔軟嵌段共聚物: 合成、相形態、與光電性質之研究

Fluorene Based Rod-coil Block Copolymers: Synthesis, Morphology and Photophysical Properties

童宜峙(Yi-Chih Tung)

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(2009年)

https://doi.org/10.6342/NTU.2009.00058

摘要

芴系硬桿-柔軟嵌段共聚高分子近年來由於其在光學元件的廣泛應用而備受矚目。軟段高分子的導入不但能改善芴系高分子的光電特性，更能增加其應用性。然而，分子構性、相形態、及加工性(靜電紡絲)對芴系高分子光電性質影響的研究還不完善。本論文藉由設計不同分子構性的芴系硬桿-柔軟嵌段共聚高分子來探討分子構性、相形態對芴系高分子光電性質影響。並且討論使用不同溶液來製備的靜電紡絲纖維對相形態與光電特性的影響。

本文的第一個部分(第二章)為研究芴系硬桿-柔軟嵌段共聚高分子在溶劑狀態下的相形態，並且探討相形態對光電特性的影響。吾人合成兩種芴系硬桿-柔軟嵌段共聚高分子，聚芴-聚壓克力酸與聚芴-聚矽氧烷壓克力嵌段共聚物。藉由調控鏈段比例與溶劑的選擇性而使聚芴-聚壓克力酸共聚高分子在溶劑狀態下能形成多變的微胞結構。包括球型、柱狀、泡囊狀等的高分子微胞結構。實驗結果顯示，微胞的結構變化深受高分子的鏈段比例與溶劑的選擇性影響。而微胞結構的變化會使芴系高分子產生H形態的聚集進而影響其光電特性。另一方面，分別探討對硬桿端選擇性溶劑與柔軟端選擇性溶劑對聚芴-聚嵌段共聚高分子相形態與光電特性的影響。在聚矽氧烷壓克力的選擇性溶劑中，能形成多變的相形態並且造成芴系高分子產生聚集而影響其光電特性。而在聚芴端的選擇性溶劑中，無法形成多變的相形態並且不會影響到芴系高分子的光電特性。

本文的第二個部分(第三章)為探討靜電紡絲對芴系硬桿-柔軟嵌段共聚高分子的相形態與光電特性的影響。實驗結果顯示使用不同溶劑所製備的纖維，會形成不同形態的微結構，進而影響其光電特性。本章節更深入探討硬桿-柔軟嵌段共聚高分子的靜電紡絲纖維用於pH 感應器方面的應用。結果顯示不同溶劑製備的纖維，其對酸的感應程度隨著硬桿端高分子的聚集程度上升而下降。而由靜電紡絲製備的纖維會比其固態薄膜的感測性高

本文的第三個部分(第四章)合成不同鏈段比例的側鍊型芴系高分子與嵌段共聚物，並探討不同溶劑(四氫氟喃、甲苯、二甲基甲醯胺)對光電特性的影響。實驗結果顯示側鍊型芴系嵌段共聚物的吸收與放射光譜在四氫氟喃、甲苯的溶液中不會受到高分子組成的影響。然而在二甲基甲醯胺的溶液中，側鍊型芴系嵌段共聚物的量子效率會隨聚芴段的組成增加而降低。固態放射光譜的結果顯示柔軟段高分子的導入會造成芴系高分子產生紅位移並且改變放射光譜的位置。此外，不同溶劑揮發度也會對相形態的造成影響。使用高揮發的溶劑(四氫氟喃)製備的薄膜會形成不規則的孔洞、球狀、球狀聚集的形態。而使用低揮發的溶劑(甲苯)製備的薄膜會形成較規則的孔洞、球柱共存、繩狀、與島狀結構。而這些結構形成的驅動力是來自於聚芴端高分子的聚集而產生的微相分離。

關鍵字

硬桿-柔軟嵌段共聚物 ； 芴系高分子 ； 靜電紡絲

並列摘要

Polyfluorene based rod-coil block copolymers have been widely studied recently due to their potential applications on optoelectronic devices. Such block copolymers could not only manipulate the electron and optoelectronic properties but also provide the flexibility on morphology control. However, the effects of molecular architecture and phase behaviors on photophysical properties of such polymers have not been fully explored. In this thesis, both main chain and side chain fluorene based block copolymers were used to explore the effects of molecular architecture and morphology on photophysical properties.

In the first part of this thesis (chapter 2), two kinds of rod-coil block copolymers, poly[2,7-(9,9-dihexylfluorene)]-block-poly(acrylic acid) (PF-b-PAA) and poly[2,7-(9,9-dihexylfluorene)]-block-poly[3-(trimethoxysilyl)propyl methacrylate] (PF-b-PTMSPMA) with different coil lengths in dilute solution are reported. Tape-like lamellar morphology was observed at a short coil length of PF-b-PAA. As the coil length increased, the large compound micelle, sphere, or vesicle was observed with different methanol contents due to the enhancement on the PAA swelling with methanol and the interfacial tension between the PF core and PAA corona. A further increase on the coil length, an inverted morphology of sphere or rod with PF corona and PAA core was shown first but the core/corona was reversed at a high methanol content resulted from the enhanced solubility of PAA. The morphological transformation led to a significant variation on optical absorption or fluorescence characteristics due to the possible H-aggregation formation. On the other hand, micelle morphologies of the PF-b-PTMSPMA in THF/MeOH or THF/EA mixed solvents are characterized by transmission electron microscopy (TEM) and scanning force microscopy (SFM). Ethyl acetate (EA) and methanol (MeOH) were used as selective solvents for the PF rod and PTMSPMA coil blocks, respectively, while THF as the common solvent. In the THF/MeOH mixed solvent, PF-b-PTMSPMA assembled into diverse morphologies of sphere, short cylinder, cylinder, and cylinder bundles. Besides the selective effects, the strong π-π interaction of PF contributed partially to the above morphologies. In the THF/EA mixed solvent, morphologies of the PF-b-PTMSPMA changed from large compound micelles (LCM) to hollow spherical micelles due to the strong core chain stretching. Stable micelles were obtained by crosslink -Si(OR)3 groups of the PTMSPMA block by triethylamine (TEA). The micellar morphology significantly affected the photophysical properties. In the THF/MeOH mixed solvent, blue shifts on the UV-vis and fluorescence spectra were observed, probably attributed to the formation of the H-aggregation in the PF core. However, the photophysical properties were insensitive to the different ratios of THF/EA, due to the insignificant aggregation of short PF corona. The present study revealed that the morphology and photophysical properties of fluorene based rod-coil polymers could be significantly manipulated through solvent, rod/coil ratio, and

並列關鍵字

rod-coil ； polyfluorene ； electrospun

參考文獻

[2] I.W. Hamley, The Physics of Block Copolymers; Oxford University Press: Oxford,

England, (1998)

[3] C. Booth, C. Price, Comprehensive Polymer Science; Pergamon Press: Oxford, England, (1989)

[6] M. Muthukumar, C.K. Ober, E.L.Thomas, Science 277 (1997) 1225.

[7] M. Lee, B.K. Cho, W.C. Zin, Chem. Rev. 101 (2001) 3869.