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標題: Self-assembly of Symmetrical Poly(oxyalkylene)-diamidoacid Copolymers
作者: 王棋禾
Wang, Chi-He Stephen
關鍵字: Self-assembly;自我排列
出版社: 化學工程學系
The study involves the preparation of sodium salts of poly(oxypropylene)-trimellitic amidoacid copolymers (POP-amidoacid), the interface property, self-assembly, morphological changes in molecular self-assembly, and molecular manipulation.
1. Sodium salts of poly(oxypropylene)-trimellitic amidoacid copolymers (POP-amidoacid), prepared from the reaction of POP-diamines and trimellitic anhydride, were found to self-assemble into orderly molecular bundles. The POP-amidoacid has a symmetrical structure consisting of a hydrophobic POP middle block (2000 g/mole) and four symmetrical carboxyl end groups. By dissolving in water and evaporating on a polyether sulfone film, the POP-amidoacid molecules self-assembled into a unique array with average dimensions of 7-13 nm in width, 2-5 nm in height, and 20-50 nm in length, observed by atomic force microscope. Varied morphologies were also observed when varying the pH, solvents, evaporating rate, concentration, and substrate surface. Unlike the common surfactants of single head-to-tail structure and the naturally occurring phospholipids of one-head and two-tails, the synthesized POP-derivative is a symmetrical structure of four hydrophilic heads and one long hydrophobic block. Through the complementary noncovalent bonding forces, the molecules tend to align into molecular bundles or loops as the primary structure. The formation of different morphologies is controlled by the intermolecular forces including hydrogen bonding, aromatic π-π stacking, ionic charge, and hydrophobic interaction, in a concerted manner.
2. Changes in molecular self-assemblies from poly(oxypropylene)-trimellitic amidoacids or imidoacids have been investigated by using dynamic mode atomic force microscopy (DFM). Imidoacids were prepared from a ring-closure of amidoacids at high temperature. Through DFM continuous scanning, different self-assembled morphologies from amidoacid and imidoacid were observed. Besides the multiplicity of carboxyl functionalities, the backbone variety (oxypropylene vs. oxyethylene) and molecular weight (2000 g/mol vs. 400 g/mol) are important factors affecting the self-assemblies on polyether sulfone surface. These copolymers were found to be amphiphiles demonstrating an ability of lowering interfacial tension at the toluene/water interface. Their surfactancy and self-assembling properties are attributed to the complimentary forces in the structures.

本論文討論有關商業化聚醚胺類 (Jeffamine® poly(oxyalkylene)-amine)與偏苯三酸酐(Trimellitic anhydride, TMA)所合成的共聚合物 poly(oxypropylene)-trimellitic amidoacid copolymers (POP-amidoacid),並探討此聚合物之界面性質、自排性質並探討分子的型態變化,進一步了解操控分子排列的方法。
1. 利用偏苯三酸酐和雙胺官能基的聚醚胺類所合成的共聚合物POP-amidoacid,能夠形成有規則的分子束自我組裝特性。POP-amidoacid 擁有對稱性結構的共聚合,結構的中間鏈段是親油性的POP結構而兩邊尾端鏈段含有四個對稱性的羧基結構。先將POP-amidoacid共聚合物溶解在水中後,利用旋轉塗佈的方式將試樣分散在高分子PES基材的表面上後藉由原子力顯微鏡的量測,結果觀察到此共聚合物的一級結構以及規則排列的分子束型態。透過酸鹼度、溶劑、分散速率、濃度以及基材種類的變化會影響分子的排列情形。POP-amidoacid 共聚合物有別於一般界面活性劑的頭對尾結構或是自然界的磷脂物質一個頭對兩個親油性的尾結構,而是一個具有四個親水性連接一段長鏈的親油性區段之對稱性結構。透過互補的非共價鍵作用力,會使分子趨向延伸而堆積成為分子束或是分子自身環繞而形成環路物質。在此形成不同分子型態的機制主要是由聯合的非共價鍵力量所控制,其中這些作用力包括氫鍵、離子鍵、苯環的π-π作用力以及凡得瓦爾力的力量決定。
2. POP-amidoacid以及POP-imidoacid分子的自我排列的變化性已藉原子力顯微鏡可明顯觀察而得。POP-2000/2COOH (POP-imidoacid) 分子是由POP-2000/4COOH (POP-amidoacid) 分子在高溫下經過閉環的反應而得到的產物。透過原子力顯微鏡不斷掃描,可進一步了解到POP-amidoacid與POP-imidoacid不同分子的排列型態。並探討影響分子的排列因素,其中包括相同結構之官能基變化,不同主鏈鍛分子,以及不同分子量。最後探討形成不同分子排列型態以及具有降低在水/甲苯的界面張力現象,其原因主要是結構上的作用所致。
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