利用Cu2+/HSO3-氧化還原系統合成PMMA乳膠顆粒及其熱裂解研究

[[abstract]]本研究利用無乳化劑乳化聚合的方式，以不同濃度的Cu2+/HSO3-氧化還原系統作為起始劑合成聚甲基丙烯酸甲酯(PMMA)乳膠顆粒，計算單體轉化率、乳膠顆粒大小和Zeta電位及其熱性質。實驗結果發現不同起始劑濃度合成出的PMMA的轉化率皆可達90%以上，Zeta電位皆小於-30mV，表示乳液的穩定性佳。以SEM觀察乳膠顆粒的形態，結果顯示乳膠顆粒大小均一分佈，粒徑大小隨起始劑濃度增加而變大，此趨勢與光散射儀的結果一致。雖然改變起始劑濃度，PMMA乳膠顆粒仍有幾乎相同的玻璃轉移溫度(124~126℃)。PMMA乳膠顆粒的TGA曲線圖顯示二階段式的裂解行為，第一階段屬不飽和末端基團PMMA-CH=CH2的熱裂解，第二階段屬飽和末端基團PMMA-H的熱裂解。隨著起始劑中銅離子濃度增加，可衍生較多的不飽和末端結尾PMMA-CH=CH2，以致於在第一階段形成較多的熱重損失。利用Ozawa法計算，可獲得二階段的裂解活化能，隨著飽和末端基團PMMA-H越多，第二段裂解活化能(Ea2)越高。[[abstract]]In this study, poly(methyl methacrylate) latex was synthesized in an emulsifier-free emulsion polymerization using a Cu2+/HSO3-redox initiator system. In addition to the monomer conversion, particle size, zeta potential, and thermal properties of polymer latex were also investigated under different concentrations of redox initiator. The experimental results showed that the monomer conversion reached above 90% for all systems. Zeta potential was all negative and magnitude was greater than 30mV, which showed the stability of PMMA emulsion. The morphology of the latex observed by FESEM revealed an uniform particle size and the average particle size decreased with increasing the concentration of redox initiator. PMMA latexes have almost the same Tg, 124~126 .degree.C, regardless of the concentration of redox initiator. The TGA curves of PMMA latex showed two stages of thermal degradation, which were caused by the degradation of unsaturated end group (PMMA-CH=CH2) and saturated end group (PMMA-H), respectively. The higher the concentration of Cu2+ ion, the more the proportion of PMMA-CH=CH2 in product, and in turn giving more weight loss in the first-stage degradation. The apparent activation energies of two stages were estimated by Ozawa's method. As the saturated end group (PMMA-H) increased, the apparent activation energy in the second-stage (Ea2) is raised.[[sponsorship]]台灣大學高分子科學與工程學研究所；中華民國高分子學會[[conferencedate]]20070119~20070120[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]臺北市, 臺