聚苯胺之合成及其特性研究

Synthesis and characterization of polyaniline

湯秀靜(Shiow-Jing Tang)

指導教授 ： 邱寬城

中原大學/理學院/應用物理研究所/博士(2011年)

https://doi.org/10.6840/cycu201101017

摘要

在本論文中，我們依序對聚苯胺（PANI）的合成條件與製備過程，及其相關之特性量測與導電機制作了一番詳盡的探討。在第二章中，我們藉由調控氧化劑過硫酸銨（APS），鹽酸（HCl）與苯胺（Aniline, 簡稱AN）這三者之莫耳濃度比例（[APS]:[HCl]:[AN]）來探討AN聚合之初始條件對後續產物特性的影響。在 [APS]/[AN] = 0.23與[AN] = 0.27 M的前提下，藉由AN與HCl的相對濃度大小提出一個簡易判斷AN聚合機制的架構，並將其分成三種類型：(A) [AN] >> [HCl]，(B) [AN] 稍大於[HCl]，以及(C) [AN] < [HCl]。當系統初始狀態為（A）類型時，溶液中主要組成為電中性的AN分子，產物為類吩嗪苯胺寡分子（Phenazine-like aniline oligomer, PZAO）。當系統初始狀態為（C）類型時，溶液中主要由苯胺陽離子構成，產物為PANI。 當系統初始狀態屬於（B）類時，則產物同時具有（A）類型與（C）類型的特徵。
在第三章中，我們將鹼性之半氧化半還原態的PANI粉末，在壓力p為250 ~ 10000 psi的條件下壓製成錠。將Au/PANI/Au架構的電性量測樣品置於真空致冷系統中進行暗電導率 σ 隨抽氣時間與溫度變化的實驗。利用拉長指數函數（Stretched exponential function）對σ 隨抽氣時間的變化趨勢作數值擬合（numerical fitting）所得到指數  與衰退時間 來分析水汽由樣品兩側逸出的行為。接著使用一維變程（1 D variable range hopping）跳躍與熱活化 (Arrhenius nearest-neighbor hopping) 模型來分析電導率隨溫度變化趨勢，並探討電荷載子在樣品內之傳輸行為。
在第四章中，根據第二章的實驗結果，我們製備了具有片狀結構的PZAO，奈米粒/片狀結構的PANI/PZAO複合材，以及奈米粒/奈米絲結構的PANI等三種粉末。將此三種材料在剛合成好（As-prepared），去摻雜 (De-doped) 與再摻雜 (Re-doped) 的狀態下壓成錠，並進行一系列變溫的電導率量測。由熱活化，準一維（quasi-1D）與三維變程跳躍（3D variable range hopping）模型來作數值擬合並分析載子在材料內之傳輸機制。剛合成好的與在摻雜後的PANI樣品皆具有較高的電導率σDC 與微弱的變溫趨勢，其活化能EA分別只有4.8 與18 meV，具有較長的局部化長度L，並在費米能階處具有很高的能態密度N(EF)。去摻雜後的PANI樣品具有較大的EA (520 meV)與較小的L與N(EF)。PZAO樣品由於缺乏長的共軛結構，因此σDC 均極低。剛合成好的與再摻雜的樣品EA均很高(510 and 580 meV)，去摻雜的樣品 EA更高達870 meV。剛合成好的與再摻雜的PANI/PZAO複合材樣品，在320 K時具有相對較高的σDC 與較低的EA (33 and 41 meV)。去摻雜後的樣品，EA 相對較高(420 meV)，並且具有較低的σDC。最後在第五章中作個總結。

關鍵字

聚苯胺 ； 電導率 ； 跳躍躍遷 ； 苯胺寡聚物 ； 導電機制 ； 熱活化能 ； 合成機制

並列摘要

Effects from various initial molar ratios of aniline, APS, and HCl ([AN]:[APS]:[HCl]) on the polymerization of aniline were investigated. First, a scheme derived from a molecular point of view was proposed to distinguish the formation mechanisms based on their initial conditions. Then, by choosing a relatively low ratio of [APS]/[AN] = 0.23 at [AN] = 0.27 M, three cases can be categorized according to this scheme: (A) [AN] >> [HCl], (B) [AN] slightly larger than [HCl], and (C) [AN] < [HCl]. For case (A), the initial solution has a richness of neutral anilines. Both the doped and dedoped samples are confirmed to have features of phenazine-like oligomers. For case (C), neutral anilines are almost protonated to become anilinium cations. The final products possess features of polyaniline. For case (B), the samples possess both features from cases (A) and (C). Finally, the formation mechanisms for polymerization of aniline were discussed.
Polyaniline (PANI) films consisted of emeraldine base (EB) powders made by various pressing pressures p and sandwiched by two Au-electrodes are characterized by current-voltage (I-V) measurements. A linear behavior in I-V curves is observed and from which the dark electrical conductivity  of the sandwiched Au/PANI/Au sample is deduced. The sample is then put into a cryostat to study the variations in  upon dynamic vacuum-pumping and under cooling processes. During dynamic vacuum-pumping process, H2O molecules inside the film are gradually removed from the lateral edge, thus,  decreases. The temporal decay in (t) of these dedoped PANI films can be fitted via a stretched exponential function and from which the decay exponent  and decay time constant  associated with the diffusion of H2O molecules out of the as-pressed film can be obtained. The relations for  and  with respect to p are discussed, respectively. Next, by measuring the temperature dependence of (T) of these dedoped PANI films, the charge-carriers transport is discussed in terms of 1D variable-range-hopping model and Arrhenius activated-barrier-crossing model, respectively. Finally, the physical significance from the fitting results is discussed.
Electrical characterization of pelletized samples made from polyaniline (PANI), phenazine-like aniline oligomer (PZAO) and PANI/PZAO composite together with the effects from de-doping and re-doping were studied. A numerical fit by using Arrhenius nearest-neighbor hopping, quasi-1D and 3D variable-range hopping models was applied. For samples composed of PANI nanogranules/nanofibers obtained at high [HCl] = 1.0 M, both as-prepared and re-doped samples possess high σDC with a weak T-dependence due to the dopants effects; and small EA (4.8 and 18 meV) for nearest-neighbor hopping and large L and N(EF) for quasi-1D and 3D variable-range hopping were obtained. After de-doping, low σDC with a strong T-dependence was obtained and large EA (520 meV) and small L and N(EF) were resulted. For samples composed of planar PZAO structure obtained at [HCl] = 0.10 M, σDC becomes very small. Both as-prepared and re-doped samples possess high EA (510 and 580 meV), and after de-doping EA increases (870 meV). For samples composed of PANI/PZAO composites obtained at [HCl] = 0.20 M, both as-prepared and re-doped samples possess relatively high σDC at 320 K and low EA (33 and 41 meV); and after de-doping, EA increases again (420 meV).

並列關鍵字

carrier transport ； formation mechanism ； conducting mechanism ； polyaniline ； phenazine ； hopping ； conductivity

參考文獻

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