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標題: Effects of Sodium Dodecyl Sulfate on the Phase Transition Behavior of PAAc-PEG-PNIPAAm Graft Copolymers in Aqueous Solution
作者: 陳睦親
Chin, Chen Mu
關鍵字: 十二酯硫酸鈉
polymeric micelle
出版社: 化學工程學系
摘要: Abstract In this study, the effects of sodium dodecyl sulfate on the phase transition behavior of PAAc/PEG/PNIPAAm graft polymers in aqueous solution at temperatures below and above its critical micellization temperature (CMT) were evaluated by dynamic light scattering, fluorescence spectra and variable temperature 1H-NMR measurements. The results indicate that the polymer-induced SDS micelles were formed via their extensive interactions with the PNIPAAm grafts as the SDS concentration was higher than its critical aggregation concentration (CAC). With increasing temperature, polymer-induced micelles were destroyed by the thermally-induced hydrophobic aggregations of PNIPAAm grafts. A significant portion of SDS molecules existed at the micellar interface and stabilized the micelles at reduced sizes. Significant increase in the T1 values of the PEG and PNIPAAm graft also confirmed the binding of SDS micelles with PNIPAAm grafts in polymer aqueous solutions. These evidences support our suggestion that the SDS micelles bound with PNIPAAm grafts prevent the mixing of PEG and PNIPAAm grafts through hydrophobic interaction and hydrogen bonding at lower temperatures and lead to the decrease in inter-core PEG bridging at higher temperatures. As a results, more core/shell distinct polymeric micelles of smaller sizes were accordingly obtained.
摘要 本篇研究主要探討SDS濃度對於接枝高分子水溶液相變化行為之效應。吾人由螢光光譜儀方式,測量接枝高分子各組成與SDS之間的交互作用力,並輔以核磁共振光譜儀(1H-NMR)的數據證實PNIPAAm-induced micelle的存在;當SDS濃度大於臨界聚集濃度(CAC)時,PNIPAAm鏈段上的isopropyl group將被SDS分子包覆在內部,降低接枝側鏈PNIPAAm與PEG之間的纏繞,使得高分子微胞核層內部solid/liquid-like core的比例增加,微胞粒子將更加紮實及緻密。 由實驗中發現,接枝高分子溶液的臨界聚集溫度(CAT)隨著SDS濃度的增加而往高溫處位移,這是SDS的吸附造成接枝高分子鏈段需要有較大的能量與鏈段上的電荷密度相互抗衡;另一方面,當接枝側鏈PNIPAAm開始聚集後,鏈段上的SDS將被帶入疏水區域內,因此雙性結構的PNIPAAm-induced micelle將受到破壞而鑲崁於殼-核界面處,最後可由動態光散射粒徑儀和1H-NMR之PNIPAAm上甲基質子積分值得知,SDS的導入將可獲得粒徑更小且殼-核結構更加紮實的高分子微胞。
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