透過您的圖書館登入
IP:18.118.200.136
  • 學位論文

奈米模板聚合物與膠體粒子在空乏力作用下自組裝行為的分子模擬研究

Depletion-induced Self-assembly between Nanoparticle-imprinted Polymers and Colloidal Particles: A Simulation Study

指導教授 : 諶玉真

摘要


由於奈米模板聚合物(Nanoparticle Imprinted Polymer, NIP)能夠辨識幾何結構上與其互補的粒子,而進行專一性的接合。NIP 製備成本低、機械強度高的優勢上也吸引越來越多學者投入與奈米粒子製成之模板聚合物相關的研究。其中包含官能基單體、溶劑、交聯劑種類的選擇、添加比例的探討等等,無非是希望可以增加NIP 的選擇性、特異性接合的程度。而根據一些奈米粒子自組裝的文獻中,提到當系統中含有非黏附型的高分子散佈於溶劑中時,奈米粒子會因為空乏作用力而聚集,我們也好奇此一現象是否也會在NIP 的系統中發生。因此,在本研究中,我們利用耗散粒子動力學(DPD)模擬的方式,針對由空乏力所引起之NIP 與目標粒子的自組裝行為進行探討。 首先,我們分析目標粒子在系統中所受到的平均作用力,發現即使在沒有添加高分子的情況下,當基板與目標粒子間沒有親和作用力,僅具有與目標粒子幾何結構互補之凹槽時,目標粒子所受到的引力大於其在具有親和力的平面基板之系統中所受到的引力;此結果彰顯了基板幾何結構對於空乏作用力的重要性。因此,我們分析目標粒子及基板的幾何結構差異以及高分子的濃度對目標粒子結合比例(θa) 造成的影響。模擬結果顯示與基板幾何結構相容的目標粒子的結合比例較不相容的目標粒子高,因為與基板凹槽接合越緊密可以釋放出越大的重疊排外體積層以增加系統亂度;且在特定濃度的高分子之下,可以使不同尺寸的兩種粒子在結合比例上達到最大的差異。而體積較小的目標粒子因為與基板接合後釋放的重疊排外體積小、加上粒子本身亂度效應的關係,即使是在結構相容的基板系統中,結合比例也很低。因此,針對小體積目標粒子的系統,我們試著在此系統的基板凹槽中加上具親和力的接合位點,發現雖然空乏力或親和力的作用單獨存在時,對小體積目標粒子的結合比例影響不大,但是兩者同時作用於系統中確實能夠促進小體積目標粒子的結合比例。 此外,我們也計算目標粒子在上述系統中的平均受力以及結合能量(-Ea),發現結合能量與目標粒子的結合比例有著高度的正相關,並且同時受到粒子幾何結構與空乏分子的濃度所影響。作為基板有凹槽的系統之對照組,我們也在計算目標粒子在平面基板的系統中所受到的作用力,發現當平面基板沒有特殊接合位點(即基板整體與目標粒子的親和力相同)時,與具有特殊接合位點的平面基板之系統中, 在結合能上得到相近的結果,然而目標粒子在兩系統中的結合比例卻沒有與結合能的結果一致,原因在於目標粒子在後者的系統中,接合在基板上後的亂度下降較多,導致結合比例下降。而在無凹槽基板的系統中,我們調控兩項變數,分別為空乏分子的濃度以及目標粒子與基板的親和力,發現在幾何結構相同、沒有特殊接合位點的條件下,由於亂度在兩系統中的效應相同,因此結合比例的高低與結合能的大小表現是一致的。 最後,我們針對不同幾何結構的系統對目標粒子作二維的作用勢能圖,再搭配對目標粒子施加不同方向的拉力測試,發現從能障較低的路徑上,將粒子拉離基板所花的時間也越短,因此,從二維能量圖的結果來看,目標粒子的脫離會傾向於走能障最低的路徑,而非隨機選擇脫離路徑。根據我們二維勢能上的分析結果,我們可以大致預測粒子脫離基板的路徑,將有助於關於NIP 在實驗上或模擬上的動力學研究。

並列摘要


Since nanoparticle imprinted polymer (NIP) can recognize specific nanoparticles which possess complementary chemical and geometrical properties, there are more and more researches dedicated to NIPs for their advantages of lower production cost and higher mechanical strength. To enhance the selectivity and specific adsorption ratio of nanoparticles onto NIPs, numerous experiments were performed to identify the appropriate species as well as the relative ratios of the functional monomers, cross-linkers, and solvents. In addition, the adsorption efficiency of nanoparticles can be improved since nanoparticles tend to self-assemble with patterned NIPs due to the depletion force induced by non-adsorbing polymers. To investigate the effects of dispersant concentration and geometrical complementarity between nanoparticle and NIP, dissipative particle dynamics (DPD) simulations are employed to study the depletion-induced self-assembled behavior between targeted nanoparticle/NIPs systems. It is found that the attraction interaction strength between a nanoparticle and a substrate is larger as the substrate is with complementary cavities, rather than the substrate with patches possessing affinity binding sites. Also, it is observed that the geometric compatibility between the nanoparticles and the substrate pattern is a crucial factor affecting the self-assembly between nanoparticles and NIP substrates. The degree of targets/NIPs association increases as the geometric compatibility grows due to the significant increase in the release of the excluded volume. Moreover, the association efficiency is enhanced as the dispersant concentration rises. The depletion force and association energy of the nanoparticle/NIP systems are calculated for various geometrical conditions. It is found that the degree of association between nanoparticles and substrates increases as the association binding energy grows. Furthermore, the combination effect of the depletion attraction and binding site affinity can augment the association ratio of the systems. A two-dimensional potential profile of a substrate-target pair demonstrate that the nanoparticle tends to follow certain paths with low potential barriers to dissociate. The consequence can be helpful in studying the kinetic behaviors of nanoparticle/NIP systems. These simulation results are important in the signal enhancement of sensor applications and separation efficiency improvement of chromatography and solid extraction treatments.

參考文獻


4. H. Nishino, C. S. Huang and K. J. Shea, Angew Chem Int Ed Engl, 2006, 45, 2392-
Biotechnol Adv, 2016, 34, 30-46.
8. K. Mosbach and O. Ramström, Bio/technology, 1996, 14, 163-170.
9. R. Schirhagl, Analytical Chemistry, 2014, 86, 250-261.
12. S. Asakura and F. Oosawa, J. Chem. Phys., 1954, 22, 1255-1256.

延伸閱讀