She Yunlong, Lee Jihyung, Lee Byeongdu, Diroll Benjamin, Scharf Thomas, Shevchenko Elena V, Berman Diana
Materials Science and Engineering Department and Advanced Materials and Manufacturing Processes Institute , University of North Texas , 1155 Union Circle , Denton , Texas 76203 , United States.
Langmuir. 2019 Jan 22;35(3):796-803. doi: 10.1021/acs.langmuir.8b04039. Epub 2019 Jan 14.
Infiltration of the polymer templates with inorganic precursors using the selective vapor-phase infiltration approach, or sequential infiltration synthesis (SIS), allows the design of materials with advanced properties. Swelling of the block co-polymer (BCP) templates enables the additional control of the structure, porosity, and thickness of the composite or inorganic materials. Here, we use the highly precise quartz crystal microbalance (QCM) technique to investigate quantitatively the effect of the micelle opening by swelling and inorganic precursor infiltrating on the evolution of porosity in amphiphilic BCPs. We show that swelling of the polystyrene- block-poly-4-vinyl pyridine (PS- b-P4VP) BCP in ethanol at 75 °C occurs rapidly and results in a stable polymer structure in 30 min. By using an alumina model system, we found that swelling enables access to all available polar domains of the PS- b-P4VP film leading to an increase in the SIS-infiltrated alumina mass as compared to the nonswelled BCP layer. Our results demonstrate that swelling of the 110 nm thick BCP template results in the formation of 192 nm thick alumina films with 2 times larger alumina mass and 4 times larger effective pore volume than in case of the nonswelled sample. In the case of the thicker polymer template, the difference due to swelling becomes even more substantial because the fraction of accessible polymer is increased much more than in thin films. Our findings provide important insights into the mechanism of the infiltration of the inorganic precursors into swelled and nonswelled, spin-coated BCP templates enabling the design of highly porous thick ceramic films by SIS.
使用选择性气相渗透法或顺序渗透合成法（SIS），用无机前驱体渗透聚合物模板，能够设计出具有先进性能的材料。嵌段共聚物（BCP）模板的溶胀能够额外控制复合材料或无机材料的结构、孔隙率和厚度。在此，我们使用高精度石英晶体微天平（QCM）技术，定量研究溶胀和无机前驱体渗透对两亲性BCP孔隙率演变的影响。我们发现，75℃下聚苯乙烯-嵌段-聚-4-乙烯基吡啶（PS-b-P4VP）BCP在乙醇中的溶胀迅速发生，并在30分钟内形成稳定的聚合物结构。通过使用氧化铝模型体系，我们发现，与未溶胀的BCP层相比，溶胀使得能够进入PS-b-P4VP薄膜的所有可用极性区域，从而导致SIS渗透的氧化铝质量增加。我们的结果表明，110nm厚的BCP模板溶胀后，形成的氧化铝薄膜厚度为192nm，氧化铝质量是未溶胀样品的2倍，有效孔隙体积是其4倍。对于较厚的聚合物模板，由于溶胀导致的差异变得更加显著，因为可及聚合物的比例增加幅度远大于薄膜。我们的研究结果为无机前驱体渗透到溶胀和未溶胀的旋涂BCP模板中的机制提供了重要见解，从而能够通过SIS设计出高度多孔的厚陶瓷薄膜。
