Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/3480
標題: Preparation and phase transition behavior of PAAc-PNIPAAm-PEG graft copolymers in aqueous solution
PAAc-PNIPAAm-PEG接枝高分子之製備與水溶液中相轉移行為之探討
作者: 陳建憲
Chen, Chien-Hsien
關鍵字: micelle;微胞;thermal sensitivity;PNIPAAm;amphiphilic;graft;熱敏感性;聚氮異丙基丙烯醯胺;雙性;接枝
出版社: 化學工程學系
摘要: 
The graft polymer composed of polyAAc as polymeric mainchain, PEG and PNIPAAm as grafting sidechain at an elevated temperature in aqueous solution can self-assemble to form micelle structure with innercore and outershell. The chemical structure and composition of copolymer were characterized by FTIR and NMR. Other properties depended on temperature were measured by density analyzer, florescence spectroscopy, NMR, and DLS.
Under the LCST, the phase transition behavior of copolymer in aqueous solution was dependent on PNIPAAm concentration, but it was depended on composition of copolymer above the LCST. It was also observed that the contents of PNIPAAm in the polymeric micelle core at high temperature were not disappeared completely from NMR. The result suggests that there are two kinds of degree of mobility in the micelle core for PNIPAAm. The region of greater mobility was defined as liquid-like interface layer, and that of less mobility was solid core.
Moreover, we also found that the diameter of micelle was decreased with temperature increased, and stabilized without intermolecular aggregation at high temperature, owing to a PEG shell induced to the micelle.

由於PEG具有排斥的作用,而PNIPAAm具有溫度敏感之特性,因此我們設計一雙性高分子,以polyAAc作為主鏈,mPEG及PNIPAAm作為側鏈之接枝共聚合高分子,此高分子具有溫度應答之特性,且同時帶有親水性鏈段及疏水性鏈段,可因溫度變化產生可逆性相轉移之特性使此高分子於高溫水相中自我排列形成微胞結構。我們以相同分子量、不同比例之PNIPAAm製備不同高分子,並利用FTIR、1H-NMR確定其結構並定出其組成,再以密度儀、螢光光譜儀、1H-NMR、動態光散射儀探討高分子隨溫度變化之關係。研究中我們發現,不同組成之接枝高分子,其LCST會有些微的不同,約為33~34℃,但與PNIPAAm比較起來,LCST的改變非常小,而相轉移的溫度範圍會變寬。隨著溫度的增加,高分子會形成微胞結構,其臨界微胞濃度會隨著PNIPAAm含量的增加而變大。從螢光的分析實驗中也發現不同組成之高分子所形成的微胞結構,其內部之親疏水性也會有所不同,當疏水鏈段比例較大,形成微胞後之疏水性較強。另外從1H-NMR中可看出高分子微胞之PNIPAAm含量會隨著溫度的升高先些微升高而後降低,升高的部分是因為溫度升高導致spin-lattice relaxation time升高,形成微胞後,因PNIPAAm進入核層造成流動性降低,導致偵測到的含量下降,但是我們發現核層內之PNIPAAm會有流動程度不同的情形,流動性較差之部分屬於solid-like core,流動性較佳的部分屬於liquid-like layer,這項發現與其他文獻僅有solid-like core或liquid-like core有很大的不同。此外我們還發現,當溫度低於LCST時,性質之變化與高分子濃度較有關係,而溫度高於LCST時,由於高分子已形成微胞,因此結構的影響則較為重要,且PNIPAAm含量越高,相轉移的程度較為明顯,且其過程也較短,所形成之結構也較為緻密。粒徑測量的結果也顯示微胞在高溫下能達到平衡,且粒徑不再繼續變化,這表示我們所加入的PEG具有排斥的作用,可以防止微胞之間進一步的聚集。
URI: http://hdl.handle.net/11455/3480
Appears in Collections:化學工程學系所

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