有機鈷金屬錯合物CoII(Salen*)在可控/活性自由基聚合反應上的應用

The Application of Cobalt Salen Complexes in Controlled/Living Radical Polymerization

廖哲民(Chie-Ming Liao)

指導教授 ： 彭之皓

國立清華大學/理學院/化學系/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00382

摘要

摘要
用CoII(Salen*)成功地進行醋酸乙烯酯(vinyl acetate, VAc)和丙烯酸甲酯(methyl acrylate, MA)的活性/可控式自由基聚合反應。得到的符合活性特徵的聚醋酸乙烯酯(poly(vinyl acetate), PVAc)和聚丙烯酸甲酯(poly(methyl acrylate), PMA)。
在VAc的聚合反應系統中，PVAc高分鏈的分子量與單體轉換率呈線性成長，而且可以達到60%以上的單體轉換率和較窄的PDI值(1.09~1.25)。在反應過程中所有CoII(Salen*)會全部轉換成CoIII(Salen*)-R，我們推估其系統有很大的平衡常數(Keq ~ 109 M-1)。此外CoIII(Salen*)-PVAc也被合成出來，在添加物THF和pyridine的幫助下成功地進行鏈延伸聚合反應。單體轉換率可以到50%，而且高分子鏈的成長接近理論分子量。
在MA的聚合反應系統中，也得到PMA高分鏈的分子量與單體轉換率呈線性成長，達到60%以上的單體轉換率和較窄的PDI值(1.20~1.30)。紫外光-可見光光譜儀追蹤CoII(Salen*)在MA聚合反應中並不會全部轉換成CoII(Salen*)-R，而是會達到平衡。因此我們可以藉由數值分析方法計算出CoII(Salen*)在MA系統的平衡常數(Keq = 2.4 × 107 M-1)。從反應的自由基濃度可以推論出CoII(Salen*)在VAc聚合反應中主要是以等價交換反應(degenerative transfer, DT)主導高分子的成長，而在MA的系統中是以可逆鏈終止反應(reversible termination, RT)為主要的反應路徑。
用CoIII(Salen*)-PVAc當作大分子起使劑進行MA聚合反應，在額外添加CoII(Salen*)的條件下能成功合成出PVAc-b-PMA嵌段共聚物，此外PVAc-b-PAN也成功地被合成出來。

關鍵字

活性自由基聚合反應 ； 聚丙烯酸甲酯 ； 聚醋酸乙烯酯

並列摘要

Abstract
The cobalt(II) [N,N‘-bis(3,5-di-tert-butylsalicyli-dene)-1,2-cyclohexanediamine] (CoII(Salen*)) could be mediated in the controlled/living radical polymerization of vinyl acetate and methyl acrylate successfully. The poly(vinyl acetate) (VAc) and poly(methyl acrylate) (MA) with living characters were obtained.
In VAc system, the PVAc polymer chains were growth with conversion linearly and agree to the theoretical molecular weight. The conversion could arrive to 60% with narrow polydispersity index (PDI) were between 1.09 and 1.25. All CoII(Salen*) transform to CoIII(Salen*)-R during induction period. Because of one chain per catalyst, the equilibrium constant could be estimated (> 109 M-1). The macro-initiator, CoIII(Salen*)-PVAc was also synthesized and could be performed in the PVAc chain extension with additives (THF and pyridine).
In MA system, the PMA with high conversion (> 60%) and low PDI (1.20~1.30) were obtained. The polymer chains were growth with conversion linearly and agree to the theoretical molecular weight. The equilibrium between cobalt(II) and organo-cobalt(III) species in methyl acrylate polymerization was followed by UV-vis spectroscopy and the equilibrium constant was determined to be 2.4 × 107 M-1. The kinetic studies showed the mechanism of polymerization of VAc could be degenerative transfer (DT) major and the MA system could be reversible termination (RT) major.
The facile formation of block copolymers of PVAc like PVAc-b-PMA (poly(vinyl acetate)-block-poly(methyl acrylate)) and PVAc-b-PAN (poly(vinyl acetate)-block-poly(acrylonitrile)) illustrates the unusual capability of the cobalt Salen* catalyst system to generate new applications in materials science.

並列關鍵字

Living Radical Polymerization ； CoII(Salen*) ； poly(methyl acrylate) ； poly(vinyl acetate)

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