利用分子模擬探討高分子刷在無溶劑條件下的平衡結構與動態行為

Abstract

奈米粒子—有機混成材料(Nanoparticle—organic hybrid materials)是一種無溶劑的奈米複合材料，由無機中心核與嫁接在表面的有機高分子刷組成。在無溶劑的情況下，系統的流動性來自於嫁接的高分子。此研究是利用粗粒化分子模擬(Coarse-grained molecular dynamics simulations)預測當兩顆奈米粒子距離很近時，忽略粒子的曲率且將系統簡化成兩個平板上分別嫁接著高分子，其高分子結構以及相對應的能量分佈為何，並強調高分子刷的多分散性。此外，透過分析高分子鏈端點間擾動的自相關函數、Rouse mode擾動的自相關函數以及高分子鏈端點間的均方擾動來加以描述動態特性。本研究發現增加高分子的嫁接密度和鏈長會導致更長的鬆弛時間，且結果顯示出無溶劑的高分子刷系統和單一條嫁接的高分子系統皆偏離Rouse理論預測。

Nanoparticle organic hybrid materials (NOHMs) are a solvent-free nanocomposite composed of inorganic cores and tethered polymeric brushes. The fluidity of the system is originated from the tethered polymers. To investigate interparticle in NOHMs, ignoring the curvature of the particles, we present a coarse-grained molecular dynamics study of a system of end-grafted polymer chains between parallel surfaces and put emphasis on polydispersity in polymer brushes. Monomer volume fraction profiles and corresponding energy components are presented. We have also analyzed the end-to-end fluctuation autocorrelation function and Rouse mode fluctuation autocorrelation function and the mean square end-to-end fluctuation in order to depict the polymer chains relaxation. Increasing grafting density and chain length leads to increase the corresponding relaxation times. Additionally, we find that the solvent-free polymer brushes system and single tethered polymer system deviate from rouse predictions.