- 學位論文
烯烴聚合物及其奈米複合材料之合成與應用
Synthesis and Application of Olefin Polymers and Polyolefin Nanocomposites
摘要
本論文主要分為兩大部分，（一）利用有機茂金屬觸媒進行烯烴單體聚合反應，其中包括乙烯、丙烯及甲基丙烯酸甲酯之單質聚合反應和乙烯、4-甲基-1-戊烯及甲基苯乙烯之共聚合與三聚合反應，再經由活性自由基聚合反應合成丙烯和乙烯段式與接枝共聚物；（二）利用溶液混摻與單體聚合的方式，在無機材黏土的存在下，合成聚甲基丙烯酸甲酯、聚苯乙烯及聚丙烯奈米複合材料。 有機茂金屬觸媒在目前工業及學術上受到相當大的注目，除了本身具有高度聚合活性之外，所生成的聚合物可以經由不同結構的觸媒控制其分子量、分子量分佈與立體結構。本研究在不同的反應條件下，利用rac-Et(Ind)2ZrCl2觸媒進行丙烯聚合反應，藉此可獲得不同性質之丙烯聚合物。此種觸媒經由鏈轉移至單體終止反應之後，可以得到末端不飽和基之聚丙烯。不飽和基與9-BBN在氧氣的環境下，於聚丙烯的鏈末端生成自由基，經由此自由基引發共聚合反應，得到丙烯與甲基丙烯丙甲酯段式共聚物。 有機茂金屬觸媒具有共單體效應，可得到比例較高且均勻的共聚物。本研究將乙烯與甲基苯乙烯直接進行共聚合反應，甲基苯乙烯共單體會均勻分佈於聚乙烯主鏈上形成亂排的共聚物結構。位於苯乙烯上的甲基利用溴化反應可轉換成溴甲基，將此一溴甲基作為起始劑，利用銅觸媒進行分子轉移自由基聚合反應，加入甲基丙烯酸甲酯與丙烯酸丁酯共單體，可以得到接枝共聚物。所得之段式和接枝共聚物皆可以作為界面調和劑，於混摻時可以降低因極性不同所造成的界面張力，以獲得高度均勻分散摻合共聚物。 利用rac-Et(Ind)2ZrCl2觸媒，合成出聚(乙烯-co-4-甲基-1-戊烯)共聚物與聚(乙烯-ter-4-甲基-1-戊烯-ter-甲基苯乙烯)三聚物，於不同反應條件下，可以控制這兩種聚合物之單體組成、分子量及熱性質，且共單體可以均勻地分散至聚乙烯主鏈之間。4-甲基-1-戊烯單體具有正共單體效應，可以增加共聚合反應之觸媒活性及產量。此兩種新型的彈性體材料，可以取代目前線性低密度聚乙烯於工業上的應用，其熔點及玻璃轉移溫度可以由不同的共單體組成獲得控制，且分子量分佈也較小。 含官能基單體，例如甲基丙烯酸甲酯，因為官能基部分會和有機茂金屬觸媒的活性中心產生錯合反應，造成觸媒活性降低甚至消失。加入一路易士酸（二乙基鋅）先行與含官能基單體進行錯合，可以降低毒化觸媒活性中心的機會。利用Cp2YCl(THF)觸媒可以於低溫下獲得高產率與高對排特異性之聚甲基丙烯酸甲酯，和IVB族有機茂金屬觸媒不同之處，Cp2YCl(THF)觸媒可以在沒有助觸媒（甲基氧化鋁）的情況下進行甲基丙烯酸甲酯之聚合反應，且立體特異性比加入助觸媒時來的高。 於有機聚合物之中，添加層狀無機材（黏土）可以增加聚合物本身的機械強度、熱性質、硬度與耐磨性等，此一複合材料屬於奈米級複合材料，目前此一材料最大的問題，在於如何將無機添加材均勻地分散至有機基材內，讓有機基材的性質有較大的提昇。我們選用蒙脫土作為無機添加材料，利用聚甲基丙烯酸甲酯之溶液插層及層間聚合（包括苯乙烯懸浮聚合法與丙烯原位聚合法）兩種方式，利用官能基與黏土片層的作用力與聚合時所產生的爆發力破壞蒙脫土的層間結晶，於穿透式電子顯微鏡下可以清楚看出剝離狀之蒙脫土片層均勻分散至聚烯烴基材內，其熱裂解溫度、玻璃轉移溫度、熔點、模數與硬度等性質都有明顯的提昇，此一複合材料可以在不破壞聚烯烴本質得情況下提昇其使用年限，可以應用於光電及半導體產業上，提高材料的應用性。
並列摘要
In this study, it contains two parts, (1) the synthesis of polyolefins and its copolymers by metallocene catalyst system; and the synthesis of graft and block copolymers through living free radical polymerization; (2) the synthesis of polyolefin-clay nanocomposites by using the solution intercalation and the monomer polymerization. An isotactic chain-end unsaturated polypropylene can be prepared by the homogeneous metallocene catalyst rac-Et(Ind)2ZrCl2 with MAO. Herein, the chain end unsaturated polypropylene proceeded the hydroboration reaction to prepare borane-containing polypropylene. By introducing oxygen, the borane-containing polypropylene will produce free radicals at the chain-end. Experimental results indicated that the macromolecular free radical is an effective initiator for the polymerization of methyl methacrylate to produce diblock poly(propylene-b-methyl methacrylate). The copolymerization reaction can also be proceeding with ethylene and p-methylstyrene via metallocene catalysts. The bensylic protons of p-methylstyrene are ready for many chemical reactions, such as halogenation and oxidation, which can introduce functional groups at the p-methyl group position under mild reaction conditions. With the bromination reaction of poly(ethylene-co-p-methylstyrene), we could prepare polyethylene graft copolymers, such as poly(ethylene-g-methyl methacrylate) and poly(ethylene-g-t-butyl acrylate) through atomic transfer radical polymerization. The following selective bromination reaction of p-methylstyrene units in the copolymer and the subsequent radical graft-form polymerization were effective to produce polymeric side-chains with well-defined structure. In the bulk, the individual polyethylene and poly(methyl methacrylate) segments in the graft copolymer are phase-separated to form crystalline polyethylene domains and amorphous poly(methyl methacrylate) domains. The microscopy results reveal the effectiveness of poly(ethylene-g-methyl methacrylate) in the polymer blends by reducing the phase sizes, improving the dispersion, and increase interfacial interaction between domains. The poly(propylene-b-methyl methacrylate) copolymer can also be proven to be an effective compatibilizer in the polypropylene and poly(methyl methacrylate) blends. Two new elastomers, i.e. poly(ethylene-co-4-methyl-1-pentene) and poly(ethylene-ter-4-methyl-1-pentene-ter-4-methylstyrene) could be prepared by rac-Et(Ind)2ZrCl2 catalyst. The comonomer composition, molecular weight and thermal properties were controlled by different reaction conditions. The 4-methyl-1-pentene comonomer had positive comonomer effect that increase the yield and catalyst activity in the copolymerization and terpolymerization. The melting point and glass transition temperature of copolymer and terpolymer were very sensitive with the comonomer composition. Methyl methacrylate was polymerized with Cp2YCl(THF) or IVB group metallocene compounds (Cp2ZrCl2 and Cp2HfCl2…etc), in presence of a Lewis acid, Zn(C2H5)2. The Lewis acid was complexed with methyl methacrylate that avoided the metallocene compounds to be poisoned with functional group. A living polymerization was promoted through the use of metallocene/MAO/ZnEt2 which gave tactic poly(methyl methacrylate) with high molecular weight. When the polymerization temperature exceeded the room temperature, the poly(methyl methacrylate) could not be synthesized by the Cp2YCl(THF) catalyst. However, when the reaction temperature reached down to -60oC, the higher syndiotatic and the higher molecular weight of poly(methyl methacrylate) can be obtained by Cp2YCl(THF)/MAO catalyst system. Recently, polymer-clay hybrid materials have received considerable attention from both a fundamental research and application. This organic-inorganic hybrid, which contains a nano-scale dispersion of the layered silicates, is a material with greatly improved physical and mechanical characteristics. These nanocomposites are synthesized through in-situ polymerization or direct intercalation of the organically modified layered silicate into the polymer matrix. In our study, the poly(methyl methacrylate)-clay, polystyrene-clay and polypropylene-clay nanocomposites would be prepared by solution intercalation, suspension polymerization and in-situ polymerization. The thermal and mechanical properties had significantly increase with the clay exfoliation in the polymer matrix.