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標題: | 多對鎖鑰粒子在空乏力作用下之自組裝行為的分子模擬研究 Assembly of Nanodispersed Key Lock Colloids Induced by Polymeric Depletants |
作者: | Chang-Wei Huang 黃常維 |
指導教授: | 諶玉真(Yu-Jane Sheng) |
關鍵字: | 分子自組裝,奈米粒子,膠體, Self-assembly,nanoparticles,colloids, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 近年來,越來越多的研究專注於粒子的自組裝行為分析,當系統中含有非黏附型的高分子散佈於溶劑中,且高分子與奈米粒子間無特殊作用力時,奈米粒子會因空乏作用力而聚集。空乏力的產生發生於任何幾何結構的型態,因此相當多的研究重心在於分子幾何結構的建造。特別的是,學者成功地在奈米粒子上製作出特殊凹槽,製備出類似鎖頭的不對稱幾何型態,這樣特殊形態的鎖狀結構會在空乏力的作用下與鑰形奈米粒子產生選擇性的鍵結行為,因此吸引廣大的注目與討論。在本研究中,我們利用耗散粒子動力學(DPD)模擬法,針對由空乏力所引起之多對分散之奈米鎖鑰形粒子自組裝行為進行研究。
在系統中,我們發現鍵結型態可以分成鎖鑰鍵結與鎖型自身鍵結兩種型態,而鍵結型態將隨著空乏分子濃度與粒子幾何結構差異而有不同的聚集行為。為了將系統簡化為單一型態之鎖鑰型鍵結,我們透過鎖型粒子表面上的接枝結構,避免了鎖型自身的鍵結,因而達到單一鎖鑰鍵結的型態,以利後續分析。 我們分析鎖鑰粒子間幾何結構差異造成的鍵結比例,可以發現幾何結構的相容性是影響鎖鑰鍵結的關鍵因素,接合越緊密的鎖鑰粒子可以釋放出最大的重疊排外體積層,此模擬結果也與實驗結果相當吻合。在空乏分子的結構上,我們針對空乏分子濃度與鏈段長度進行探討,當系統存在足夠的空乏分子時,會使鎖鑰粒子靠近時受到空乏吸引力進而形成鍵結。然而,如果空乏分子長度太短,將無法幫助鎖鑰粒子形成鍵結,若太長,對於鍵結的助益並不顯著。另外,當系統溶劑與空乏分子的交互作用力在溫度的變化下,而產生溶解度的差異,亦會造成鍵結型態上的影響。 我們亦計算粒子鍵結時的平均受力與鍵結能量,可以發現鍵結能量與鍵結比例有著高度正相關的關係,並且受到粒子幾何結構與空乏分子的變化所影響。粒子鍵結反應平衡常數中的鍵結體積是難以估量的參數,因此我們透過帶入鍵結比例與鍵結能量,可以間接獲得鍵結體積。特別的是,當系統空乏分子的物理條件變動時,在相同的幾何結構下所獲得之鍵結體積相當一致。隨著幾何結構的不同將造成鍵結體積的差異,幾何相容性愈高且粒子越大者,其鍵結體積愈小,原因則是來自於鑰型粒子在鎖型凹槽內的轉動程度變小所致。因此,從總體結果可以看出鍵結能量與排外層體積的重疊量正相關,然而鍵結體積的大小趨勢則是取決於粒子在鍵結凹槽中的轉動程度。最後,藉由平衡常數的計算,我們可以找到粒子幾何結構之間的選擇性趨勢,進而瞭解空乏分子在濃度、長度、結構硬度與不同溶劑中的熱力學性質,進一步印證實驗上的觀察並且提供奈米粒子在自組裝行態上定量的分析及預測。 Self-assembly has become the most common term for the autonomous aggregation over the past decade. In colloidal suspensions containing large and small particles a peculiar attraction force appears, which can lead to the aggregation of large particles. Especially, if a non-adsorbing polymer (depletant) is introduced into a colloidal system flocculation has often been observed. Recently, it is possible to experimentally synthesize a lock-like particle by producing a cavity on a spherical particle. The selectivity of binding between lock nanoparticles and the corresponding key nanoparticles induced by depletion force triggers wide discussion and investigation. In this thesis, we adopt dissipative particle dynamic (DPD) method to explore the depletion-induced self-assembled behavior between key and lock particles in the nanodispersed system. It is found that the lock-lock binding can be avoided by grafting polymers onto the convex side of the lock particles. The key-lock binding increases as the concentration and size of the depletants increase. Moreover, for a temperature responsive polymeric depletant, the size of the depletant varies with temperature and thus the binding capability of lock and key particles can be manipulated by adjusting temperature. Furthermore, it is observed that the geometric compatibility between key and lock particles is a crucial factor for lock-key binding. The degree of key-lock binding increases as the compatibility grows due to the significant increase in the overlapping of the excluded volume. Furthermore, we calculate depletion forces and binding energy between one pair of key and lock particles at different distances, and the binding fraction is consistent with the binding energy trend. Also, the binding volume can be derived via equilibrium constant. This consequence demonstrates that binding volume varies with geometric shapes resulting from different degree of rotational diffusivity of the key within the cavity. As the geometric compatibility between the key-lock binding is weak, the binding volume tends to grow due to the increase in the orientational rotation. Also, binding volume depends only on geometric shapes of the lock and key irrespective of the physical characteristics of the depletants. Our simulation results are in consistent with the experimental findings. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/54065 |
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顯示於系所單位: | 化學工程學系 |
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