奈米銀粒子與光硬化環氧樹脂-銀奈米複合材料之製備及性質研究

Abstract

本實驗以三丙二醇（Tripropylene glycol）單體為Polyol製程之反應還原劑，並添加保護劑聚乙烯基吡咯烷酮（Poly(vinylpyrrolidone)，PVP）以控制粒子生成而製備不同尺寸與形狀的奈米銀粒子，並加入光硬化環氧樹脂（UV-curable Epoxy）中製成銀-環氧樹脂奈米複合材料，以探討銀之添加對奈米複合物試樣介電性質的影響。傅氏轉換紅外光譜（Fourier-transform Infrared Spectroscopy，FTIR）與核磁共振光譜（Nuclear Magnetic Resonance Spectroscopy，NMR）分析顯示，Tripropylene glycol在合成銀粒子之反應過程中能形成帶有醛類官能基之中間物，以此中間物還原銀離子使生成銀粒子。穿透式電子顯微鏡（Transmission Electron Microscopy，TEM）與X-光繞射（X-ray Diffraction，XRD）等之分析顯示利用Polyol製程與所採用之還原劑可生成34 nm銀粒子之形狀大小；氮氣環境中之熱重損失分析（Thermogravimetric Analysis，TGA）顯示加入銀粒子使得奈米複合試樣之熱穩定性變差，乃因聚合度不佳所致；介電常數之量測顯示，添加2 wt.%，粒徑為63 nm之銀粒子的奈米複合物試樣之介電常數可提升至5左右（純環氧樹脂介電係數值約在3左右），且在量測頻率100 Hz至1 GHz範圍內，樣品的極化機制並無變化，介電常數較高的樣品，同時具有較低的漏電流，故有應用於軟式電子元件中之高介電材料之潛力。

The silver (Ag) nanoparticles were prepared via the polyol process using tripropylene glycol as the reducing agent and poly(vinylpyrrolidone) (PVP) as the protecting agent. The Ag nanoparticles were also added into the UV-curable epoxy to form the nanocomposite resin and its dielectric properties were investigated accordingly. FTIR and NMR analyses revealed that tripropylene glycol transforms into the aldehyde compound and then reduces the Ag ions to Ag particles during the synthesis. TEM and XRD analyses revealed that the Ag particles as small as 34 nm can be formed via the polyol process within the selected reducing agent. TGA in N2 ambient showed that the thermal stability of the nanocomposite resin deteriorates due to addition of Ag particles which causes the incomplete polymerization. As shown by dielectric constant measurement, the sample containing 2 wt.% of 63-nm-in-diameter Ag nanoparticles exhibited the dielectric constant as high as 5 (the dielectric constant of reference epoxy sample is 3). The values of dielectric constants did not change with the measuring frequencies in the range of 100 Hz to 1 GHz, indicating the polarization mechanism remains the same in such a frequency span. The leakage current density was found to decrease with the increase of dielectric constant, evidencing the promising applications of UV-curable epoxy-Ag nanocompsite films to flexible electronics as the high dielectric constant material.