OPV系列分子之合成與其自組裝光電超分子奈米結構、有機/無機掺和及其性質探討

Abstract

在本研究中，我們成功地利用Horner-Wittig Reaction合成出Oligo(2,5-bis(octyloxy)-p-phenylene vinylene) (OHC-Tri-BOPV-CHO)，並與較早之前實驗室合成出來的Oligo(2,5-bis(hexyloxy)-p-phenylene vinylene) (OHC-Tri-BHPV-CHO)共同做一系列的光學性質、自組裝奈米結構與有機/無機掺和實驗的探討和比較。利用UV-vis光譜及PL光譜來研究OHC-Tri-BOPV-CHO、OHC-Tri-BHPV-CHO以chloroform、hexane、decane為指定溶劑時不同濃度之溶液態光學性質，並且進一步研究藉由旋轉塗佈所形成的固態薄膜，其光學特性及與溶液間的差異。經由分析我們發現：UV光譜的高峰強度增加皆與溶液的濃度變化成正比；且當溶劑由極性改為非極性溶劑時，不論是溶液或薄膜固態的UV圖譜皆會有藍位移的現象，薄膜固態的螢光特性則會有紅位移的現象產生；固態的UV光譜與螢光光譜和溶液的UV及PL圖譜相較下皆有紅位移的現象。此外，我們又將OHC-Tri-BOPV-CHO、OHC-Tri-BHPV -CHO 溶在不同的溶劑下(hexane、decane、chloroform、THF)，以AFM及TEM觀測其溶劑中不同濃度下的自組裝結構，其自組裝結構出現濃度與PL光譜分析結果一致，我們並利用其分子結構的組成與觀測到的自組裝結構結合起來，提出一個modle來描述OHC-Tri-BOPV-CHO及OHC-Tri-BHPV-CHO系列分子之間堆疊的機制，其驅動力為偶極矩作用力與π-π堆疊交互作用力，OPV系列分子在溶液中由於π-π堆疊交互作用力使π共軛分子彼此平行排列且偶極矩作用力使側邊醛基部分相連而向兩旁延伸排列，由此形成極薄的片狀結構，而OHC-Tri -BOPV-CHO由於側鏈烷鏈段較長，其空間與能量不足以使片狀結構整個向上捲起為管狀，因此在適當的濃度下僅能在邊緣處稍微捲起( 在hexane中) ，或是藉由排列形成長板型的條狀結構(在THF中) ，甚至有上下堆疊的情形產生(在chloroform中)。相較之下，OHC-Tri-BHPV -CHO則由於側鏈烷鏈段較短，片狀結構向上捲起為中空管狀時除了可降低表面能外，也提供側鏈烷鏈段足夠的伸展空間，因此在適當的濃度下可以形成中空管狀結構(在THF中)，或是藉由片狀結構的堆疊而形成條狀結構(在chloroform中)。最後，我們以OHC-Tri-BOPV-CHO、OHC-Tri-BHPV-CHO在THF中形成的管狀自組裝結構為基礎，進行Titania與Silica兩個系列不同濃度比的有機/無機摻合實驗，得出最佳化的濃度比例，兩組系列的主要差異在於：Titania掺和實驗的主要發光波長較為紅移、與Silica掺和之螢光結構呈條狀且長度較長，而與Titania掺和之螢光結構則呈現較粗短且緻密的網狀結構。

In this research, oligo(2,5-bis(octyloxy)-p-phenylene vinylene) (OHC-Tri-BOPV-CHO) was successfully synthesized via the Horner-Wittig Reaction. A series of experiments including optical properties, investigation of self-assembly nanostructure and organic/ inorganic hybrid had been done on OHC-Tri-BOPV-CHO and oligo(2,5-bis(hexyloxy)-p-phenylene vinylene) (OHC-Tri-BHPV-CHO). We used UV and PL to study the optical properties of OHC-Tri-BOPV-CHO and OHC-Tri-BHPV-CHO compounds dissolving in the chloroform, hexane, and decane and in solid thin films by spinning coating. From the UV spectroscopy, the intensity of absorption peaks increase with solution’s concentration. And the compounds dissolving in different solvent showed the absorption peaks would be blue-shifted with increasing the solvent polarity while the PL peaks red-shifted. Nevertheless, the solid thin films always showed red-shifted in both UV/vis absorption and PL spectra compared to the compounds in solutions. Moreover, the self-assembly nanostructure of compounds in different solvent (hexane、decane、chloroform、THF) and concentration was also investigated by AFM and TEM. The change of self-assembly nanostructure with the concentration was parallel with the result of PL investigation. It is believed that the driving forces for all above self-assembly processes were the combination of dipole-dipole interaction, π-πinteraction, and Van der Waals force. The compounds of OHC-Tri -BHPV-CHO in THF self-assembled to form a very thin film, which tended to roll up into a hollow tubular structure to decrease the surface energy. Due to the longer length of side chain, OHC-Tri-BOPV-CHO molecules could only arrange into plank-like long stripes structure in THF and slightly roll up at film edge ( in hexane ), or even stack up with each other ( in chloroform ). At last, we took the tubular self-assembly structures of OHC-Tri-BOPV-CHO and OHC-Tri-BHPV-CHO in THF solvent as a structure base to further study the hybrid nano-strucutures with titania and silica.The result showed that the wavelength of luminescence of the titania hybrid series was red-shifted compared to the silica hybrid series, and the luminescent structure of the silica hybrid series has longer length but less dense than that of the titania hybrid series.