殼聚醣�氧化石墨烯複合薄膜於奈米結構特徵及滲透蒸發效能之分子模擬解析

Abstract

本研究利用一種結合分子動態力學與部分量子力學運算的多尺度模擬技術來研究經交聯之殼聚醣�氧化石墨烯複合薄膜的奈米結構特徵與輸送行為。近年來此種類有機�無機複合材料被認為可以克服傳統高分子膜在滲透蒸發分離效能上會遇到的權衡限制。殼聚醣薄膜材料上有許多親水官能基可以吸引極性分子，再加上用於複合的氧化石墨烯碎片具有多數高速水分子通道，能進一步提昇對水的親和性而增加滲透蒸發應用整體的分離效能，而藉由添加戊二醛產生交聯的結構則可以減緩薄膜操作時產生的澎潤效應。本論文利用模擬方法來探討以氧化石墨烯作為填充相對於薄膜結構及分子輸送行為所帶來的加乘性。 然而，由於複合薄膜內部複雜的結構，要有效率地建立模擬模型又能精確預測其效能仍然是一大挑戰。在此研究中我們結合了分子尺度與量子尺度建立一個新的模擬流程來有策略性地完成複合薄膜的模擬。同時我們也預先進行了純殼聚醣及經交聯之殼聚醣薄膜的模擬與研究來驗證我們的模擬方法，結果顯示模擬模型的性質和實驗數據吻合。最後我們藉由水、乙醇與異丙醇三種蒸汽分子於膜材內部之恆溫吸附與自擴散的研究評估並比較了不同薄膜的分離效能。

A multi-scale simulation techniques combined molecular dynamics (MD) and certain quantum mechanics calculations were used to investigate the nanostructural features and transport behavior of the crosslinked chitosan (CS)/graphene oxide (GO) mixed matrix membrane (MMM). In recent years this kind of composite membranes is regarded as a promising one to overcome the inevitable tradeoff of the pervaporation separation performance in polymeric materials. The CS membrane comprises a large quantity of hydrophilic groups to attract polar molecules, and the incorporated GO sheets with high speed water channels can further enhance the water affinity, improving the performance of pervaporation applications. The crosslinked structures are formed by adding the crosslinker glutaraldehyde (GA) to reduce the swelling effect. The synegestic effects of GO fillers on membrane structures and transport behavior are studied via simulation methods in this thesis. However, it is still a challenge to construct MMMs model efficiently and to predict their performance precisely due to the complex structures. In this study we build a new scheme combining molecular scale and quantum scale to achieve the modeling works of MMMs strategically. Meanwhile, the pure CS polymeric membrane and the crosslinked CS membrane were also studied and modeled in advance to verify the simulation methods. As a result, the properties of simulated models agreed well with experimental works. Finally, we estimated and compare the separation performance of the different membrane models by exploring the adsorption isotherm and the self-diffusion process of water, ethanol, and isopropanol vapor molecules within the membrane materials.