Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran IR 11155, Iran.
Department of Chemical Engineering, University of Guilan, Rasht IR 41335, Iran.
J Phys Chem B. 2022 Jan 13;126(1):308-326. doi: 10.1021/acs.jpcb.1c08192. Epub 2021 Dec 27.
Microfluidic synthesis methods are among the most promising approaches for controlling the size and morphology of polymeric nanoparticles (NPs). In this work, for the first time, atomistic mechanisms involved in morphological changes of polybenzimidazole (PBI) NPs in microfluidic media are investigated. The multiscale molecular dynamic (MD) simulations are validated with the literature modeling and experimental data. A good agreement is obtained between the molecular modeling results and experimental data. The effects of mixing time, solvent type, dopant, and simulation box size at the molecular level are investigated. Mixing time has a positive impact on the morphology of the PBI NPs. Microfluidic technology can control the mixing time well and engineer the morphology of the NPs. In the process of morphological changes, at the optimum time (about 11.5 ms), the attraction energy between the polymer molecules is at the highest level (-37.65 kJ/mol). The size of the polymer NPs is minimal (2.3 nm), and the aspect ratio and entropy are at the lowest level, equal to 1.07 and 11.024 kJ/mol·K, respectively. It was found that the presence of water leads to the precipitation of polymeric NPs owing to the dominance of hydrophobic forces. Both dimethylacetamide (DMA) and phosphoric acid (PA) improve the control of the size and morphology of NPs. However, the addition of PA has a greater impact; PA acts as a cross-linker, making PBI NPs finer and more spherical. In addition, MD simulation reveals that PA increases the proton diffusion coefficient in PBI and enhances its efficiency in fuel cells. This study paves a new efficient way for morphological engineering of polymeric NPs using microfluidic technology.
微流控合成方法是控制聚合物纳米粒子（NPs）尺寸和形态的最有前途的方法之一。在这项工作中，首次研究了原子级机制在微流控介质中聚苯并咪唑（PBI） NPs 形态变化中的作用。多尺度分子动力学（MD）模拟与文献建模和实验数据进行了验证。分子模拟结果与实验数据吻合良好。在分子水平上研究了混合时间、溶剂类型、掺杂剂和模拟盒尺寸对形态的影响。混合时间对 PBI NPs 的形态有积极的影响。微流控技术可以很好地控制混合时间并控制 NPs 的形态。在形态变化的过程中，在最佳时间（约 11.5ms），聚合物分子之间的吸引力能达到最高水平（-37.65kJ/mol）。聚合物 NPs 的尺寸最小（2.3nm），并且纵横比和熵处于最低水平，分别为 1.07 和 11.024kJ/mol·K。结果发现，由于疏水力的主导作用，水的存在导致聚合物 NPs 的沉淀。二甲基乙酰胺（DMA）和磷酸（PA）都改善了 NPs 尺寸和形态的控制。然而，添加 PA 的影响更大；PA 作为交联剂，使 PBI NPs 更细、更球形。此外，MD 模拟表明，PA 增加了 PBI 中的质子扩散系数，并提高了其在燃料电池中的效率。本研究为使用微流控技术对聚合物 NPs 的形态工程开辟了一条新的有效途径。
