不同表面型態電活性聚醯胺酸之靜電紡絲製備、鑑定及其在硫化氫氣體感測上之探討

本碩士論文的研究主軸在合成、鑑定新型的硫化氫氣體感測材料電活性聚醯胺酸(EPAA)，並利用電紡絲技術賦予此材料具有不同的表面塗佈形貌於指插式電極上，並探討具不同表面塗佈形貌之氣體感測材料在作為硫化氫氣體感測時之感測效果。在感測材料的合成部分，首先利用氧化偶合法合成胺基封端的苯胺三聚體(ACAT)，並利用核磁共振光譜儀(NMR)、紅外光譜儀(FTIR)及質譜儀(MS)等設備做產物化學結構的鑑定。進一步利用二酸酐與所合成的ACAT進行化學縮和聚合反應形成EPAA，然後進行化學縮合的亞醯胺化反應，得到電活性聚亞醯胺(EPI)的產物。所獲得的EPAA及EPI則以FTIR及膠體滲透層析儀(GPC)確認其所生成高分子的化學結構。所合成EPAA及 EPI的氧化還原性質可藉由電化學循環伏安儀(CV)及紫外光-可見光吸收光譜儀(UV-visible spectroscopy)監測實驗來確認，EPAA及 EPI的酸摻雜前及後之性質可藉由紫外光-可見光吸收光譜儀及四點探針來確定，而EPAA及EPI的親疏水性質，則利用接觸角(CA) 與熱重分析儀(TGA)進行測試。在感測元件的製作部分，將先前所合成的ACAT與二酸酐單體溶解於DMAc/THF之共溶劑中，進行聚縮合反應，以合成EPAA及EPI溶液，將其塗佈在指插式電極上並趕去溶劑，以形成具有緻密的EPAA及EPI之硫化氫感測元件。經過初步簡單硫化氫敏感度測試，發現較親水的EPAA薄膜聚有較佳的硫化氫感測敏感度。因此，後續實驗即以EPAA薄膜為主要感測研究材料，以電紡絲加工技術來調整元件表面薄膜的型態，並研究感測材料表面型態變化對硫化氫氣體的感測效果。首先，在控制高分子黏度(即分子量)的狀況下使用靜電紡絲製程加工技術，利用調控外加電壓、電紡距離等兩參數，製備出一系列不同表面積及表面型態之EPAA表面塗層於指插式電極上，可以利用掃描電子顯微鏡(SEM)確認有成功調控出四種不同表面型態(即: 薄膜、球膜、球及絲共存膜、絲膜)的氣體感測元件。硫化氫氣體感測的濃度的範圍是設定在1 ppm ~ 50 ppm之間。此具有四種不同表面型態之感測材料進行比較時之測試的項目有如下：(1) 靈敏度; (2) 氣體選擇性; (3) 穩定性及 (4) 重複性。藉由以上測試得到如下結論: (1) 四種型態之薄膜靈敏度為: 薄膜＜球膜＜球絲共存膜＜絲膜。且不同濃度之硫化氫測試，所得的靈敏度線性回歸R2值皆在0.98以上。 (2) 相較於SO2、CO2及空氣，此四種不同型態的表面感測材料皆對硫化氫氣體具有最佳的選擇性。 (3) 四種不同表面型態的感測材料對硫化氫氣體的感測皆具有重複性及穩定性。

關鍵字

電活性聚醯胺酸；靜電紡絲；硫化氫；氣體傳感器

並列摘要

The research target of this master's thesis was to synthesize and identify new type of hydrogen sulfide (H2S) gas-sensing material based on electroactive poly(amic acid) (EPAA), and functionalizing this material with different surface coating profile on the interdigitated electrode (IE) via the electro-spinning technology, and examine the effect of varying the surface coating profile of the as-prepared materials in their ability to sense H2S gas. For the synthesis of sensing materials, the amine-capped aniline trimer (ACAT) was synthesized by oxidative coupling reactions, and characterized through nuclear magnetic resonance (NMR), Fourier-Transformation infrared (FTIR) and the mass spectroscopy (MS). Subsequently, the dianhydride was reacted with the diamine of ACAT through a condensation reaction. For the polymerization process, EPAA was formed first, followed by chemical imidization to generate the electroactive polyamide (EPI). Chemical structures of EPAA and EPI were confirmed by FTIR and gel permeation chromatography. Redox properties of synthesized EPAA and EPI were confirmed by electrochemical cyclic voltammetry and UV-Vis absorption spectroscopy. The change in properties of EPAA and EPI before and after acid doping were investigated by UV-Vis spectroscopy and four-point probes. The hydrophilic and hydrophobic properties of EPAA and EPI were tested using contact angle (CA) and thermogravimetric analyzer (TGA). For the preparation of the sensing component, the previously synthesized ACAT and dianhydride were dissolved in the co-solvent of DMAc/THF. The condensation reaction was performed to synthesize the EPAA and EPI solution, coated on the IE and was oven-dried to remove the solvent, thus forming a dense film of EPAA and EPI for H2S sensing. After performing preliminary tests for H2S sensitivity, it was revealed that EPAA film with higher hydrophilicity had better sensitivity for H2S. Therefore, the succeeding experiment employed the EPAA film as the main sensing material. Electro-spinning technology was used to vary the surface morphology of the distinctive device coating, and the effect of changing their morphologies to their sensing properties was studied. In addition, the polymer viscosity (i.e., molecular weight) was controlled by tuning the applied voltage and electro-spinning distance. Thereafter, the preparation of EPAA with four distinctive surface morphologies (film, electro-spray particles, mixed particles/fibers and electrospinning fibers) on IE was fabricated. Scanning electron microscopy (SEM) was used to confirm the different surface structure types. In the detection part of H2S sensing, the sensing concentration range was set between 1-50 ppm. The efficiency of the sensing materials, with four different surface morphologies, was compared based on four essential parameters: (1) Sensitivity; (2) Selectivity; (3) Stability and (4) Repeatability. Experimental results gathered led to the following conclusions: (1) The sensitivity of the sensing materials with four distinctive morphologies was found to show the following trend: electrospinning fibers  mixed particles/fibers  electro-spray particles  smooth. Moreover, the resulting sensitivity of H2S test at different concentrations showed very good linearity having R2 value above 0.98; (2) Compared to SO2, CO2 and air, the synthesized sensing materials with four distinctive surface morphologies were optimally selective for H2S; (3) The sensing materials of four distinctive surface morphologies are repetitive response and stability to sensing of H2S gas.