雙親性ABA三段鏈共聚高分子物理性質於自組裝穿孔薄膜的影響

Abstract

智慧型薄膜指的是能夠因應環境變化，自發地調控薄膜性質，選擇性地開闔孔洞的一種新穎材料，在生醫工程中相當具有發展潛力。本研究透過耗散粒子動力學(DPD)，模擬ABA雙親性三段鏈共聚高分子(Amphiphilic ABA Triblock Copolymer)的成膜性質，並且透過在A3B14A3高分子疏水鏈段施加角度為π的鍵角力，模擬高分子疏水鏈段的軟硬程度，來研究不同硬度下高分子在自組裝薄膜時的行為與生成的效應。 在研究中，我們發現具有不同硬度的ABA高分子，薄膜構型會有所不同，甚至發現到在特定硬度區間，薄膜會出現漏斗型的孔洞通道而形成穿孔薄膜。除了觀察薄膜上的微孔性質以外，我們也觀察洞口附近的高分子形態。透過研究穿孔薄膜與封閉薄膜內部構型的相異之處，我們發現到高分子硬度會影響薄膜內部高分子構型的轉變與排列，並認為其排列的凌亂度以及發生形變的容易度對於薄膜生成孔洞有所影響，當高分子難以排列整齊，又難以彎折改變形態時，在薄膜自組裝過程中就會形成孔洞。 以此孔洞生成機制為基礎，我們嘗試改變ABA高分子的結構或是作用力，研究其對於穿孔薄膜形成的影響，發現到在雙親性高分子所形成的薄膜中，親水粒子端能保護多大的疏水粒子層表面積，對於破洞面積有很大的影響。除了能夠以不同高分子結構、選擇不同溶劑、改變粒子間不同作用力來製造孔洞以外，我們也測試薄膜的混合效應，透過混摻不同比例的不同高分子的方式製作穿孔薄膜，為智慧型薄膜的孔洞調控找到了另一種方法。

Smart membrane is a novel material which can spontaneously change its properties and selectively form funnel-like pores in response to environmental changes. The material has significant potential for applications in biomedical engineering. In this study, dissipative particle dynamics (DPD) was used to study the membrane properties formed by amphiphilic ABA triblock copolymers. We investigate the effects of chain stiffness, compatibility of A block and B block, and chain length on the behavior of the self-assembled membrane. It is found that the ABA polymers with distinct stiffness can exhibit various equilibrium conformations. Within a certain interval of stiffness, funnel-shaped channels will form and the membrane contains many perforated pores. By observing the configuration of the polymers near the pore, it is found that the stiffness affects the structure and arrangement of the polymer chain and thus is the essential factor influencing the formation of a pore. If it is difficult for the polymers to arrange themselves in an ordered formation, perforated holes will form during the self-assembly process. We have also investigated the effects of chain length and interaction parameter on the pore-forming ability of the ABA membrane. As the incompatibility of A blocks and B blocks increases, the pore size increases. On the other hand, as the A and B blocks become more solvophobic, the pore size declines accordingly. The block lengths of A and B are found to enhance and deteriorate the magnitude of the pore size, respectively. We have also found that the pore size can be regulated by mixing triblock copolymers of different pore-forming ability. The mixing ratio has great impact on the pore size distribution.