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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/3487


    題名: 甲基丙烯酸酯系列團聯共聚物為界面活性劑之迷你乳化聚合研究;Miniemulsion polymerization using a block copolymer surfactant
    作者: 林明賢;Min-Shyan Lim
    貢獻者: 化學工程與材料工程研究所
    關鍵詞: 團聯共聚物;迷你乳化聚合;苯乙烯;block copolymer;miniemulsion polymerization;styrene
    日期: 2000-07-04
    上傳時間: 2009-09-21 12:17:00 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 本研究首先利用基團轉移聚合法(Group Transfer Polymerization GTP)聚合法合成分子量分佈狹窄之團聯共聚物,並利用DSC分析不同結構共聚物分子鏈間之互容情形,接著利用團聯共聚物為界面活性劑進行苯乙烯迷你乳化聚合,觀測團聯共聚物組成及組成比例對聚合反應系統之影響,最後合成出均一粒徑微粒子。團聯共聚物組成包括:甲基丙烯酸甲酯(MMA代號M)、甲基丙烯酸二甲胺乙酯(DMAEMA代號B)及甲基丙烯酸(MAA代號A)。 DSC數據分析顯示由PMMA與PDMAEMA所組成之摻合聚合物分子鏈間互容性小,而單體組成為MMA與DMAEMA之團聯共聚物有部份互容;無規則共聚物則表現良好的互容性。另外團聯共聚物玻璃轉移現象較易受軟質段(DMAEMA)的影響,而硬質段(MMA)的影響則較小。 由疏水段單體MMA與親水段單體DMAEMA所組成之雙團聯共聚物在迷你乳化聚合法中可為一有效之界面活性劑。此雙團聯共聚物在濃度為1-2倍臨界微胞濃度(Critical Micelle Concentration CMC)時,其成核機構包括油滴成核與水相成核。比較不同組成比例雙團聯共聚物M12B12、M12B36、M18B18、M18B36、M36B36在迷你乳化聚合中行為之差異,實驗結果顯示具親疏水段雙團聯共聚物型界面活性劑對迷你油滴穩定性主要由疏水段之長短所控制,當疏水段過長時如M36,此雙團聯共聚物所製備之迷你油滴較不穩定。當疏水段縮短時,變化親水段長度對油滴穩定性影響較小。 將界面活性劑由二團聯共聚物擴展至兩性三團聯共聚物,結果顯示兩性三團聯共聚物也為一有效之界面活性劑。兩性三團聯共聚物B12M8A12濃度為1-2倍CMC時,迷你乳化聚合其成核機構主要以油滴成核為主,而濃度為10mM時則有大量水相成核發生。以兩性三團聯共聚物B12M8A12與月桂硫酸鈉(Sodium dodecyl sulfate SDS)為界面活性劑之迷你乳化聚合系統,SDS系統因具有較小初始油滴故聚合速度較快。 比較B12M4A12 、B12M8A12 、B12M16A12三種不同組成比例三團聯共聚物為界面活性劑行迷你乳化聚合行為。固定親水段長度時,不同疏水段長度之三團聯共聚物對油滴穩定性依序如下:B12M16A12 ≒ B12M8A12 > B12M4A12。當三團聯共聚物濃度為10mM所製備之粒子,在低轉化率時其分子量分布為雙分布,而在高轉化率時為單分布,故可知聚合反應初期有大量水相成核發生。 利用兩性三團聯共聚物B12M8A12為界面活性劑與AIBN為起始劑,在添加20%丙酮及B12M8A12為2倍CMC狀況下,可以合成出均一粒徑苯乙烯微粒子,且此聚合系統成核機構以水相成核為主。另外,三團聯共聚物在較低分子量時如B12M8A12 、B12M12A12,較有機會合成出均一粒徑微粒子。當分子量增加時如B24M24A16、B36M36A36最終粒子粒徑分布較寬廣。 This study firstly synthesized low-molecular weight distribution polymers using group transfer polymerization i.e., the polymers were prepared by using methyl methacrylate (MMA, M), methacrylic acid (MAA, A) or 2-(dimethylamino)ethyl methacrylate (DMAEMA, B) as monomers. DSC investigated the variations of glass transition of the polymers and the miscibility between polymer chains. Subsquently, miniemulsions based on Styrene/AIBN in the presence of hydrophilic-hydrophobic copolymers as the surfactant were developed. Finally, monodispersed microspheres were synthesized by using polyampholyte triblock copolymers as the surfactant. The data of DSC showed that the blended copolymers composed of PMMA and PDMAEMA possess less miscibility. By using both hard segment of MMA and soft segment of DMAEMA monomers for copolymerization, the block copolymers present a partial miscibility, however, the random copolymers possess a good miscibility. On the other hand, we also found that the change of glass transition temperature mainly affected by soft segment of polymer than by hard segment of polymer. A hydrophilic-hydrophobic diblock copolymer with MMA and DMAEMA segments could be function as an effective surfactant in a miniemulsion polymerization. When the concentration of the diblock copolymers was 1 or 2 times of its CMC, the nucleation mechanism of miniemulsion polymerization would include both droplet and aqueous nucleation. The effect of the composition ratio of the diblock copolymer on the stability of the miniemulsion droplets was also investigated. The data showed that the length of hydrophobic segments in the diblock copolymers dominates the stability of the droplets. The miniemulsion droplets in presence of diblock copolymers with a longer hydrophobic segment (e.g., M36) as the surfactant presented less stability. The length of hydrophilic segment would show a less effect on the stability of miniemulsion droplets as the length of hydrophobic segments in the diblock copolymers was shorter. When the diblock copolymer surfactant was further extended to triblock copolymers, the polyampholyte polymer, data showed that the triblock copolymers could also function as an effective surfactant. A miniemulsion polymerization using triblock copolymer as the surfactant was also followed the droplet nucleation mechanism. However, since the droplet size a miniemulsion polymerization system in the presence of sodium dodecyl sulfate (SDS) as the surfactant was smaller than that in the presence of triblock copolyemr (B12M8A12), and it led to faster polymerization rate. For the triblock copolymers with the same length of hydrophilic segments (e.g., B12M4A12, B12M8A12, B12M16A12), their lengths of hydrophobic segments also dominate the stability of the droplets. Among them, the surfactant efficiency of B12M16A12 is almost the same as that of B12M8A12 but higher than that of B12M4A12. However, when they were used as the surfactant in miniemulsion polymerization systems and if the concentrations were high up to 10mM, the molecular weight distributions presented two peaks at lower level of conversion and single peak at higher level of conversion. This can be the evidence of the aqueous nucleation taken place at the initial stage of polymerization. The monodisperse-polystyrene microspheres could be obtained by following conditions: the surfactant concentration (B12M8A12) of 2 times CMC, initiator concentration of 2.5wt% (AIBN), acetone of 20 vol%. On the other hand, the triblock copolymers with lower molecular weight (e.g., B12M8A12 and B12M12A12) prefer to be used to prepare monodisperse microspheres.
    顯示於類別:[化學工程與材料工程研究所] 博碩士論文

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