| 摘要: | 在混合基材薄膜製備中，其中最重要的是改善添加的分子篩與高分子薄膜之間的相容性。因為低相容性經常帶來介面上的缺陷，而換句話說，低相容性也可以說是兩者之間的低黏著性，面對這個問題，通常會有幾種改善的方法，有填料幾何形狀的變化、填料或是高分子鏈的官能基化、原位合成、界面劑等方法。對於界面劑，這種方法著重於改善添加物和聚合物之間的相容性，使得原本可能出現的缺陷不復存在。在許多研究中，這種方式多是使用離子液體，但其昂貴的價格在規模化上較不具經濟效應。因此必須尋找一種替代物，一種足夠小以填補空隙、價格便宜以進行工業上的應用並且具有良好介面間黏著性的材料為我們的目標。聚多巴胺在許多材料的界面都可以產生優秀的黏著性，而其更在許多研究中已應用於各個方面，特別是在顆粒表面形成塗層或者作為黏著劑。其廣泛且優秀的黏著性，由其苯環引起的 π-π 堆疊和 π-陽離子相互作用所貢獻的。在這項研究中，ZIF-7 和 Pebax-2533 被選為填料和聚合物。ZIF-7的配體是苯並咪唑，其和聚多巴胺一樣也含有苯環。而Pebax-2533是一種聚醚(PTMO, poly(tetramethylene oxide))-醯胺(PA12(polyamide))共聚物，其中PTMO段貢獻於氣體滲透性，而PA段則提供機械穩定性。此研究中將聚多巴胺添加到這個組合當中，以改善填料與高分子間的相容性，消除無選擇性的孔洞。此研究中使用的材料鑑定包括使用X射線繞射儀(XRD)和傅立葉變換紅外光譜儀(FTIR)來研究PDA添加對晶格結構變化和功能基團差異的影響。掃描電子顯微鏡(SEM)用於觀察PDA如何連接填料和聚合物以及微觀結構的變化。能量散射 X射線光譜學(EDS)和X射線光電子能譜(XPS)用於研究PDA、ZIF-7和Pebax 之間的元素組成和相互作用。熱重分析(TGA)和差示掃描量熱法(DSC)應用於研究混合基材薄膜和純膜的熱穩定性。接著利用氮氣在 77K 下的吸附測試來測試 ZIF-7 的孔徑和表面積分析。而在單一氣體滲透測試當中，則是使用自製儀器應用於薄膜氣體滲透率的測量。;Improving the compatibility between fillers and polymers is the primary consideration in mixed matrix membrane (MMM) fabrication. Low compatibility, or in other words, low adhesion between the filler and polymer, can lead to non-selective interfacial voids, which are a nightmare for MMMs. Various methods to address this issue can be categorized as modification of filler geometry, surface interaction, design interaction, MOF composite, in-situ synthesis, interface agent, and polymer modification.
For the interface agent, this method focuses on improving adhesion between the filler and polymer. Most of the work utilized ionic liquids (ILs) as the agent, which are expensive. Alternatively, we have searched for a material that is small enough to fill voids, inexpensive for mass application, and has great adhesion. Polydopamine (PDA) came into our sight. PDA has been applied to various aspects, particularly surface modification and metal coordination. It is known for its strong adhesion, which is contributed by its benzene ring for π-π stacking and π-cation interaction.
In this research, ZIF-7 and Pebax-2533 were applied. The ligand of ZIF-7 is benzimidazole, which also contains a benzene ring as polydopamine does. Pebax-2533 is poly(ether-block-amide), a copolymer in which the PE segment contributes to gas permeability, and the PA segment provides mechanical stability. PDA was added to this combination to improve compatibility and enhance the gas permeation performance. The performance of the optimal membrane in this work exceed the 2019 upper bound for CO2/N2 separation, with CO2 permeability of 661.8 barrer and selectivity of 61.85. This is an increase of 242% and 384% in permeability and selectivity, respectively.
Characterizations of MMMs included using X-ray diffractometer (XRD) and Fourier-transform infrared spectroscopy (FTIR) to investigate the effects on lattice structure changes and infrared spectrum differences upon PDA addition. Scanning electron microscopy (SEM) was used to observe how PDA bridged the filler and polymer and changes in microstructure. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were applied for the elemental composition and interaction between PDA, ZIF-7, and Pebax. Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC) were applied to investigate the thermal properties of MMM and neat membrane. Pore size and surface area analysis, with N2 adsorption at 77K was tested on the pore size of ZIF-7. A custom instrument for single-gas permeation, set up in the constant volume-variable pressure method, was used to measure the permeability of the membranes. The test pressure difference was 1.8 bar and the temperature was 35℃. |
