利用分散聚合法與無電電鍍法製備聚苯乙烯/銀核殼型導電複合顆粒及其性質與應用研究

Abstract

本研究利用分散聚合法與無電電鍍法製備微米級高分子/銀複合顆粒及其導電度與表面型態之探討。實驗架構是利用分散聚合法製備窄分布的高分子乳膠顆粒，接著對高分子乳膠顆粒表面進行粗化、敏化及活化等表面性質修飾，最後以無電電鍍法在高分子乳膠顆粒表面還原銀金屬，製備微米級高分子/銀導電複合顆粒。 實驗主要分為兩個部分，第一部分利用高分子型界面劑聚乙烯亞胺(PEI)及聚乙烯吡咯烷酮(PVP)在乙醇/水混和溶劑的環境下進行分散聚合法製備聚苯乙烯乳膠顆粒；以動態粒徑分析儀與掃描式電子顯微鏡觀察粒徑與表面型態，微差掃描熱卡計測定其玻璃轉移溫度。結果顯示成功製備出粒徑約3微米且粒徑均一分布之聚苯乙烯乳膠顆粒，其玻璃轉移溫度(Tg)約為98°C。 第二部分以濃硫酸與氯化亞錫對聚苯乙烯顆粒進行表面性質修飾，接著利用無電電鍍法還原銀金屬製備核殼型複合顆粒，並調整不同銀含量探討其表面型態與導電度。以電位分析儀檢測表面性質修飾後的界面電位變化；以掃描式電子顯微鏡觀察複合顆粒之表面型態，接著壓錠測量導電度。結果顯示藉由聚乙烯亞胺(PEI)作為界面劑之聚苯乙烯乳膠顆粒為核可成功製備具有均勻銀金屬殼層之導電複合顆粒。 透過本研究，不但可藉由分散聚合法成功合成出粒徑均一分布之聚苯乙烯乳膠顆粒以及利用無電電鍍法製備具有均勻銀金屬殼層之導電複合顆粒，未來更期許能實際應用於異方向性導電膜之製備。

In this study, preparation of monodispersed silver-coated polystyrene core-shell type particles (Ag-PS) has been derived from a modified electroless silver plating process. The zeta potential, morphology and conductivity of the Ag-PS composite particles were investigated to study the influence of stabilizer, silver content and other experimental parameters. This study included two parts. In the first part, polyethyleneimine (PEI) and polypyrrolidone (PVP) were served as stabilizers for producing monodispersed polystyrene latexes by dispersion polymerization. Then, the glass transition temperature (Tg), particle size, zeta potential and morphology were characterized by differential scanning calorimeter (DSC), dynamic light scattering analyzer (DLS), zeta potential analyzer, and scanning electron microscope (SEM), respectively. It was found that the Tg of polystyrene latexes was approximate to the pure polystyrene. In addition, the particle size was approximate to 3μm and monodispersed. In the second part, a series of pretreatments of the PS surface was applied to modify the surface properties such as roughness, contact area and hydrophilic character. Then, silver nuclei produced on polystyrene particles served as nucleation sites for the growth of silver shell. The zeta potential, silver content, density, conductivity, particle size and morphology were characterized by zeta potential analyzer, thermogravimetric analyzer (TGA), pycnometer, four point probe and scanning electron microscope (SEM), respectively. X-ray diffractometer and energy-dispersive X-ray spectroscopy were employed to detect the crystallinity of silver and elements of composite particle. The results showed that a dense, stable and uniform silver shell was formed on the surface of PS particles. The bulk conductivity of the Ag-PS composites could achieve 2427 S/cm with only 36 wt.% silver content. According to the results, the Ag-PS composite particles with diameters of 3μm have great potential to be used as fillers in anisotropic conductive films.