聚(7,10-仲苯并苊基乙烯)衍生物之合成及光學性質研究

Abstract

本研究之目的在於合成兩種不同側鏈取代基團之聚(7,10-苯并苊基乙烯)衍生物，取代基為癸基及雙苯環液晶基。為了增加分子量並調控光色，亦與MEH-PPV單體進行共聚。除了化學結構鑑定外，亦探討其光學、電化學及熱性質，並製作雙層高分子有機發光二極體，評估其在電激發光元件之應用潛力。 所有聚合物均採用Glich路徑聚合。聚合物1P僅為寡聚物，其玻璃轉移溫度為157 oC；聚合物2P之分子量則增為2.04×105 g/mol，其玻璃轉移溫度亦提昇為207 oC。此乃雙苯環液晶基導入之結果。 聚合物1P薄膜態之紫外-可見光最大吸收及螢光最大放射波長分別位於370及482 nm，聚合物2P薄膜態之紫外-可見光最大吸收及螢光最大放射波長分別位於365及508 nm，兩者皆具有藍綠色的螢光。CV結果顯示聚合物1P之HOMO、LUMO及能隙分別為-5.99, -3.05及2.94 eV，而2P則為-5.63, -3.05及2.94 eV。HOMO大小不同是由於聚合物2P所連接液晶基所導致。

聚合物3P之薄膜態最大吸收波長為368 nm，氧化電位為1.54 eV，其性質類似於1P；共聚物4P及6P之光學性質類似。這些材料以5P元件表現較佳，在ITO/PEDOT/polymer/Al元件結構下，亮度及電流效率分別達到202 cd/m2及0.009 cd/A。

The aim of this research is to synthesize two kinds of poly(7,10- benzacenaphthene vinylene) derivatives with two different side substituents, including n-decyl group and biphenyl liquid crystalline mesogen. In order to increase molecular weights and tune emitting colors, copolymerization was also carried out with the monomer of MEH-PPV. In addition to the identification of chemical structures, the optical, electrochemical, and thermal properties of all polymers were investigated as well. Double-layer polymer light-emitting diodes were fabricated, and their potential use in electroluminescent devices were evaluated.

All polymers were synthesized via the Gilch polymerization. Polymer 1P is an oligomer with a glass transition temperature of 157 oC. The molecular weight of polymer 2P is increased to 2.04×105 g/mol; its glass transition temperature is also increased to 207 oC, as a result of incorporating biphenyl liquid crystalline mesogen.

The maximum absorption and PL emission wavelengths of 1P thin film are located at 370 and 510 nm, respectively. The maximum absorption and PL emission wavelengths of 2P thin film are located at 365 and 508 nm, respectively. Both of them show bluish-green fluorescence. The CV analysis shows that the HOMO, LUMO, and bandgap of polymers 1P and 2P are -5.99, -3.05, 2.94 eV, and -5.63, -3.05, 2.94 eV, respectively. The difference in HOMO is due to the liquid crystalline mesogen attached to 2P chains.

The maximum absorption wavelength of 3P thin film is found at 368 nm, while its oxidation potential is 1.54 eV, which are similar to 1P. The optical properties of copolymers 4P and 6P are similar. Among these materials 5P shows better device performance. The brightness and current efficiency of 5P were reached 202 cd/m2 and 0.009 cd/A, respectively, from a device configuration of ITO/PEDOT/polymer/Al.