紫外線固化的二乙炔標記高分子自組裝於仿生之應用

Abstract

自然界中，有很多種螺旋的結構，如：去氧核醣核酸、螺旋藻、玫瑰、星雲等等。材料科學家藉由掌性傳遞效應，將掌性基團透過分子設計與化學合成導入開發出一系列分子積木，再經由分子積木間的二次作用力調控自組裝形成不同掌性的螺旋結構。 在本研究中，採用一個在紫外光下能夠光交聯的發色團分子：二乙炔，作爲高分子聚合之起始劑，透過化學合成將二乙炔導入聚苯乙烯和聚乳酸高分子鏈的末端，合成出二乙炔標記的聚苯乙烯、聚乳酸高分子。其中，二乙炔標記的聚苯乙烯能夠經由呼吸法自主裝形成單層、六角形的孔洞膜，在光線的折射、反射下，可以看到類似蝴蝶與甲蟲翅膀之光子晶體的現象。 再者，因爲聚乳酸分別有左式、右式以及消旋的形式。藉由掌性傳遞效應，將二乙炔標記的聚乳酸高分子作為分子積木，再經該分子積木本身分子間二次作用力的調控，透過圓二色光譜的觀測發現二乙炔標記的聚乳酸高分子可自組裝形成不同掌性的螺旋結構，並成功誘導二乙炔基團產生螺旋排列。 關鍵詞：自組裝、掌性效應、同相高分子、二乙炔、光交聯、圓二色性、螺旋結構、聚乳酸、聚苯乙烯、呼吸法

Helix structures can be found in nature, from the space, organism to nucleus in cells (e.g., DNA, spirulina, rose, nebula). By taking advantage of chirality transfer, homochiral polymers can form mimic helical structures by introducing chiral groups into synthetic polymers via self-assembly. Additionally, self-assembled helical structures in different length scales can be produced through secondary interactions (i.e., non-covalent bonding forces). In this study, diacetylene, which is a photo-crosslinkable upon UV irradiation and an achiral chromophore, was introduced to polymers as a chain end of polystyrene (PS) or polylactides (i.e., diacetylene-labeled poly(L-lactide) (PLLA), diacetylene-labeled poly(D-lactide) (PDLA), diacetylene-labeled poly(D,L-lactide) (PLA), and diacetylene-labeled polystyrene (PS) respectively). Diacetylene-labeled polystyrene can form the monolayer and hexagonally ordered arrays of air hole at the film by breath figure method. Interestingly, structural colors like the wing of butterfly and beetle can be clearly observed due to the light reflection and refraction from the well-ordered structures. Because of three types of polylactide (L-, D-, D,L-), we use diacetylene-labeled polylactide as molecular blocks. Using circular dichroism spectroscopy (CD) found that diacetylene-labeled polylactide can self-assemble to different chirality of helical structures by controlling secondary interactions between molecular blocks, suggesting that achiral diacetylene moieties with preferential helical orientation in space to can be successfully induced.

Keywords: Chirality, Homopolymer, Diacetylene, Photo-crosslinking, Circular Dichroism, Self-Assembly, Helix, Polylactide, Polystyrene, Breath Figure.