Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9547
標題: 銀-聚醋酸乙烯酯奈米金屬螯合物之合成與特性分析
Synthesis and Characterization of Silver-Poly(vinyl acetate) Metal Chelate Nanocomposites
作者: 黃鵲容
Huang, Chueh-Jung
關鍵字: poly(vinyl acetate);聚醋酸乙烯酯;silver nitrate (AgNO3);metal chelate polymer;silver micelle;electrical conductivity;nanocomposites;銀金屬螯合物;無機/有機奈米複合物;銀微胞;導電薄膜
出版社: 材料工程學研究所
摘要: 
無機/有機奈米複合物因同時擁有有機材料和無機材料的優點,所以近年來引起廣泛的研究興趣。無機/有機奈米複合物的合成,目前已有眾多的技術和方法被研究和開發,其中的化學法因可方便的利用化學反應增加有機相和無機相之間的化學鍵結、有效改善兩相之間不相容的現象,故而逐漸受到重視。本研究利用商業化聚醋酸乙烯酯(PVAc)為基材和硝酸銀(AgNO3)金屬前駆塩進行螯合反應,以化學法合成金屬銀/聚醋酸乙烯酯奈米複合物。
本研究首先探討聚醋酸乙烯酯-硝酸銀(PVAc-AgNO3)混成系統中的反應機構,包括聚合体基材和硝酸銀金屬前駆塩之間的螯合反應以及銀前駆塩的還原反應,並且探討生成的金屬銀對聚醋酸乙烯酯結構的影響。本研究由X光繞射(XRD)、霍式轉換紅外光譜(FTIR)、核磁共振(NMR)、場發射掃瞄式電子顯微鏡(FESEM)和光電子能譜(XPS)等儀器分析的實驗結果發現,硝酸銀金屬前駆塩的銀離子可以和聚合体鏈上官能基的氧(例如酯基氧C-O-C=O,醇基氧C-OH和羰基氧O-C=O等)進行配位反應而生成聚醋酸乙烯酯-硝酸銀金屬螯合物(MCP),並且這些與聚合体鏈的官能基形成螯合鍵的銀離子(Ag(I)),在無任何額外還原劑的添加之下,可經由甲酸溶劑的作用而緩慢的進行原位(in-situ)還原反應,而於系統中被還原成金屬銀(Ag(0))奈米顆粒。實驗結果亦顯示聚醋酸乙烯酯基材的結構會因這些金屬銀的生成而發生變化,生成的金屬銀可以催化聚醋酸乙烯酯分子鏈上部份的酯基發生水解反應,因而使得聚合体結構由原來的PVAc結構轉變成PVOH/PVAc結構。
本研究為了進一步探討金屬螯合物系統中金屬銀與聚合体分子之間的作用關係,本研究利用溶解度減少的原理,以混合的溶劑/非溶劑溶液配製金屬螯合物的微胞溶液,並且利用穿透式電子顯微鏡(TEM)觀察所形成微胞的形貌。實驗結果顯示聚醋酸乙烯酯-硝酸銀金屬螯合物的微胞是一種含銀微胞,並且微胞的形貌隨系統中硝酸銀的濃度變化而改變。當硝酸銀濃度小於0.5 wt%,則銀微胞呈現一種外部為銀殼(Ag-corona)的形貌,而當硝酸銀濃度介於1.0至2.0 wt%之間,則微胞除了呈現外銀殼(Ag-corona)的形貌之外,另出現一種中央為銀核(Ag-core)的微胞。這些結果可以說明聚醋酸乙烯酯-硝酸銀金屬螯合物系統中被還原的金屬銀奈米顆粒與聚合体分子鏈之間存在著強的作用力,以至於聚合鏈在混合溶液中依自我排列(self-assembly)能力形成微胞的同時,金屬銀奈米粒子亦能依附於聚合体鏈上隨著聚合体鏈共同形成銀微胞。
本研究亦利用聚醋酸乙烯酯-硝酸銀金屬螯合物製備金屬化的導電性複合薄膜。本研究以聚對苯二甲酸乙二酯(PET)為基板,將聚醋酸乙烯酯-硝酸銀金屬螯合物溶液塗佈上方後,於80oC烘箱中乾燥之,製得MCP/PET複合薄膜。然後將此MCP/PET複合薄膜浸入硼氫化鈉(NaBH4)水溶液中進行還原反應而得到金屬化的 RMCP/PET複合薄膜。實驗結果顯示,MCP/PET和RMCP/PET複合薄膜的導電度正比於系統中硝酸銀的濃度。對相同硝酸銀濃度的MCP/PET和RMCP/PET薄膜而言,RMCP/PET薄膜的片電阻(Rs)大約低於MCP/PET薄膜104左右。並且經由電磁波遮蔽試驗的結果顯示,硝酸銀濃度為10 wt%的RMCP/PET複合薄膜其電磁波遮蔽效能可達10 dB以上,若硝酸銀濃度增加至30 wt%,則其RMCP/PET複合薄膜的電磁波遮蔽效能更可高達30 dB。

A new chemical route for the synthesis of metal-polymer nanocomposite has been developed. Commercial poly(vinylacetate) (PVAc) was used as polymer matrix, silver nanoparticles were generated by reduction of silver nitrate (AgNO3) in PVAc matrix, and a PVAc-AgNO3 metal chelate polymer (MCP) containing both the Ag(0) crystal and Ag(I) complex ions was obtained. The reaction mechanism of the MCP system, including the coordination of polymer-Ag(I) complexes, the reduction of Ag(I) ions and the hydrolysis of PVAc chains were investigated. The results showed that the Ag(I) cations of AgNO3 were coordinated with polymer functional groups to form polymer-Ag(I) complexes, subsequently, some of the complexed Ag(I) ions were in-situ reduced to generate Ag(0) metal in MCP system, and the structure of PVAc chains was partially hydrolyzed to form an amphiphilic PVOH/PVAc structure under the catalytic effect of reduced Ag(0) metal.
To evaluate the interaction of the PVOH/PVAc chains with the reduced Ag(0), an inducing method for preparing MCP micelle solution with the use of mixed solvent/non-solvent and the morphological characterization of the generated Ag-micelles were investigated. The studies showed that a long-lasting MCP solution with stable Ag-micelles might be prepared by using a H2O/HCOOH solvent with the right composition. The TEM results showed that when the AgNO3 concentration of MCP was below 0.5 wt%, the Ag-micelles displayed a variety of Ag-corona structure, but as the AgNO3 concentration was increased to 1.0-2.0 wt%, micelles that had Ag-solid embedded in the micellar core were observed.
The MCP materials that with nanosized Ag(0) and complexed Ag(I) contained in the PVAc matrix may be chemically modified by reducing agents to improve their surface metallization and electric conductivity. To evaluate the influence of such metallization upon the electric conductivity of these MCP materials, the polyethylene terephthalate (PET) was used as substrates to prepare the MCP/PET films. The studies showed that the sheet resistance (Rs) of the RMCP/PET films, which were treated with a sodium borohydride (NaBH4) aqueous solution, was at least 4 orders of magnitude lower than that of the MCP/PET films. It was also found that the electric conductivity of both MCP/PET and RMCP/PET films increased with increasing AgNO3 content. These metallized RMCP/PET films also exhibited high electromagnetic interference shielding effectiveness (EMI/SE) that is proportional to the electric conductivity.
URI: http://hdl.handle.net/11455/9547
Appears in Collections:材料科學與工程學系

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