探討運用Gay-Berne方程式所模擬而得的噻吩分子間作用力參數對於聚噻吩自組裝行為的影響

Abstract

本論文利用Gay-Berne的位能函數來描述聚噻吩在粗粒化模型中非等向性作用力。因共軛高分子中，其鏈上具有芳香性的分子之間具有π-π方向的作用力，在真實系統中，兩個具芳香性的分子在不同位向所經驗到的作用力也是不同的。因此，等向性的作用力，如Lennard-Jones函數，用來描述粒子間的作用就顯得過於簡略了。而利用Gay-Berne此一非等向性的作用力，我們可以更加貼近地描述聚噻吩在真實系統下的高分子粗粒化模型之間的交互作用力，並利用此特性來解決粗粒化力場中方向性的問題。所以我們在全原子模擬中，透過計算兩噻吩分子在不同位向中的位能曲線，並以Gay-Berne方程式進行擬合，將擬合後的參數以粗粒化分子動力學進行模擬。藉由Gay-Berne方程式，我們可以探討π-π方向的作用力對於共軛高分子在堆疊排列時的重要性以及其接枝密度、側鏈長度對於形態的影響，並比較等向性的作用力Lennard-Jones函數與非等向性作用力Gay-Berne函數對於在描述共軛高分子的適切性。

In this study, the Gay-Berne potential is adopted to simulate the anisotropic force between the thiophens in coarse-grained model of polyalkylthiophene. The Gay-Berne potential is an anisotropic force which is successfully simulate the phase behavior of liquid crystal. For poly-3-alkylthiophene, the aryl rings on the main chain have π-π interaction and these interaction strongly affect the packing behavior of the conjugated polymers. In order to simulate the anisotropy of π-π interaction between the polymer chains, we calculate the energy curves of two monomers in different orientations then fit the curves by Gay-Berne potential. In the coarse-grained molecular dynamic simulations, the parametrized Gay-Berne model is used to simulate the main chain-main chain interaction of conjugated polymer. Base on Gay-Berne potential, it is possible to explore how π-π interaction affect packing behavior and to investigate the morphological differences between the Lennard-Jones model.