交替式共聚高分子聚醯胺型聚氨酯內超分子

Abstract

傳統高分子化學中，自組裝型高分子(self-assembled polymers)如嵌段式共聚高分子常經由共價鍵方式將單體-單體間及單體與高分子主鏈上之對應官能基間相互以連結。近年來，藉由具高度方向性及主客配對之非共價鍵方式形成自組裝型高分子之新穎結構已逐漸獲得重視。此種作用力常見於生物體內許多蛋白質、DNA、RNA及3D立體構，因此近年來向自然界取材之仿生材料發展相當蓬勃。此類新型高分子中適當強度及具方向性之多點式氫鍵作用力導致了許多特殊的物理性質。近期對於互補性單元導入高分子材料中的研究，可簡略分類為側鏈修飾及鏈尾修飾等兩種。如果我們可以控制多重氫鍵的鍵結能力，就可以間接改變超分子的型態。然而，藉由不同之多點式氫鍵作用力調控超分子中之微結構及研究直到現在仍相當具有挑戰性。於此篇研究中，我們將雙重極性(amphiphilic)之長碳鏈核鹼基，導入具有自身互補性基團及多種氫鍵作用力之聚醯胺型聚氨酯高分子中，用以研究在交替式高分子中異雙聚體(heterodimer)分子辯識的行為以及在導入之後微相分離的變化。研究結果顯示，即使在系統中仍有其它種類氫鍵的存在，異雙聚體的分子辯識使得聚醯胺型聚氨酯高分子呈現「熱插式」(plug and play)的行為。藉由U16混掺比例的不同，可使得整個高分子系統的型態有所改變並得以調控。隨著U16加入的量增加，鏈與鏈間之次級層狀結構由原本雙層之結構變成深入彼此之相互交錯狀態，並進而變成單層結構。

Self-assembled polymers such as block copolymers are usually formed through covalent linkages in conventional polymer chemistry, including bonds connecting monomer units and attaching functional groups to the polymer backbone. Recently, novel structural organizations of self-assembled polymers formed through highly directional and sufficiently strong non-covalent host-guest pairs have attracted great attention. These new polymers utilize non-covalent multiple-hydrogen-bonding interactions similar to those found in bio-molecules such as protein, DNA, and RNA to direct and modulate their 3-D topology. In addition, the moderately strong and highly directional multiple-hydrogen-bonding interactions within these new generation polymers also result in unique physical properties, such as high specificity, controlled affinity, and reversibility. In previous studies, the study on the complementary nature and its effect on material properties can be broadly classified into side chain and chain ends types. Until now, studying and controlling the microstructures within supramolecular polymers with different hydrogen-bonding motifs still remain as a challenging task. In this study, the amphiphilic alkylated nucleobase, hexadecyluracil (U16) was incorporated into poly(amide urethane) which was synthesized ourselves with self-complementary group and several hydrogen bonding motifs for the study on the heterodimer recognition behavior within the alternative polymer. Biocomplementary PAU/U16 supramolecular complexes formed in dilute DMF through molecular recognition, that is, the hydrogen bonding between the diaminopyridine (DAP) groups of the PAU and the Uracil (U) of U16. Moreover, FTIR, DSC, WAXD, SAXS, and TEM analysis provided furthur detail into the nature of self-assembly of these systems. The effect of the heterodimer recognition on the microphase separation was investigated, revealing that the heterodimer recognition led the poly(amide urethane) to possessing the “plug and play” behavior even the heterodimer recognition coincided with several other hydrogen bonding motifs. The period and morphlogies of PAU/U16 complexes can be rationally tuned by the amount of U16. Upon the adding of U16, the lamellar structure within long-range lamellar changes from bilayer to bilayer with interclated and further to monolayer.