摘要
本論文利用阻抗頻譜分析儀，在頻率範圍 20 Hz ~ 3 MHz 下，量測高分子、高分子複合材料之介電特性，並探討材料內部的載子傳輸機制。首先討論聚苯胺 (PANI) 樣品。將化學氧化還原法合成之聚苯胺粉末鹼化，溶於 NMP 溶劑內，以澆鑄法製成去摻雜聚苯胺 (PANI EB) 薄膜樣品，再經由 HCl 摻雜製成再摻雜聚苯胺 (PANI ES) 薄膜樣品。PANI EB 薄膜樣品於低頻之電導率約為 1×〖10〗^(-11) S/cm，擁有較小的介電損失 (1 ~ 0.03) 及較小的介電係數。而 PANI ES 薄膜樣品能夠透過共軛 π 鍵進行載子傳遞，低頻下電導率約 2×〖10〗^(-6) S/cm，擁有較大的介電損失 (100 ~ 1)，且因酸摻雜的Cl- 離子會誘發偶極矩，於低頻下擁有較大的介電係數。其次探討聚亞醯胺 (PI) 薄膜樣品於製程中不同的熱縮合 (thermos-imidization) 溫度 (150℃, 270℃, 350℃) 對分子鏈內部不對稱及親水官能基密度的影響。PIB-270℃ 與 PIB-350℃ 兩個樣品於高溫下閉環較完全，其介電係數較小且對頻率之變化較不敏感。而 PIB-150℃ 樣品因尚未閉環完成，擁有不對稱之親水官能基，可以觀測出其介電係數較大且為頻率之函數，其介電損失也比較大。再則比較有摻雜碳黑 (PI/CB) 與沒有摻雜碳黑之聚亞醯胺 (PI) 薄膜樣品之介電特性。PI/CB 在室溫下於頻率約 200 Hz 介電損失有一吸收峰值 (f_max)，且 f_max 隨量測溫度上升而上升，符合 Debye relaxation 現象。由 Arrhenius Plot 計算出其異質介面中的極化行為對應之活化能為 340 ± 13 meV 。最後本文探討摻雜不同重量百分比之金屬有機架構與環氧樹脂之複合材料 (epoxy/MOFs) 薄膜樣品的介電特性。由於本實驗使用之 MOFs 配位基有親水性 NH2 官能基，故此樣品由抽真空的條件下移出，暴露於大氣時，因吸收水氣導致介電係數上升，其對應 Debye relaxation 之 f_max 隨暴露時間增加而上升，並在 72 小時後達到平衡。
並列摘要
The effect of charge transport mechanism on the dielectric properties of polymers and polymers/composites has been studied by impedance spectroscopy in frequency range from 20 Hz to 3 MHz. At first, the polyaniline (PANI) samples were discussed. The PANI powder synthesized from chemical oxidative polymerization was de-doped by NaOH, dissolved in NMP solvent, and then casted in the form of polyaniline emeraldine base (PANI EB) thin film. Whereas the polyaniline emeraldine salt (PANI ES) thin film was redoped by putting PANI EB thin film into an HCl solvent for 24 hours. The PANI EB thin films had low conductivity about 1×〖10〗^(-11) S/cm, low dielectric loss (1 ~ 0.03), and low dielectric constant at 20 Hz. On the other hand, the PANI ES thin films with charge transport by π-π bonding possessed high conductivity (2×〖10〗^(-6) S/cm) and high dielectric loss (~ 100) at 20 Hz. The counter ions from acidic dopants also contributed the polarization density and led to a large dielectric constant. Next, polyimide (PI) samples were made by using different thermos-imidization temperatures (150℃, 270℃, and 350℃) to control the asymmetry along polymeric chains and the density of hydrophilic functional groups. Compared to PIB-270℃ and PIB-350℃, PIB-150℃ sample had more hydrophilic functional groups, and hence showed a sensitive frequency dependence of dielectric constant and possessed a larger dielectric loss. Then, the polyimide samples with and without carbon black (PI/CB and PI) were chosen to study their dielectric properties. A dielectric absorption peak (f_max) was observed at around 200 Hz in PI/CB at room temperature. This peak increased with increasing temperature, which was matched to the Debye relaxation model. An activation energy of 340 ± 13 meV corresponding to interface polarization in heterostructure was calculated from the Arrhenius plot. Finally, the dielectric properties of epoxy samples mixed with different weight percentages (1, 5, 15, and 20 wt%) of UiO-66-NH2 (epoxy/UiO-66-NH2) were studied. Because of the hydrophilic functional groups in UiO-66-NH2, as the samples removed from the vacuum system to atmospheric environment for measurement, the adsorbed water molecules resulted an increasing dielectric constant with respect to time, and the corresponding fmax for Debye relaxation was shifted to higher frequency and approached to nearly equilibrium after 72 hours.
參考文獻
延伸閱讀
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