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Edge Charge Neutralization of Clay for Improved Oxygen Gas Barrier in Multilayer Nanobrick Wall Thin Films
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2016-12-08 00:00:00 , DOI: 10.1021/acsami.6b12937 Yixuan Song 1 , David A. Hagen 1 , Shuang Qin 1 , Kevin M. Holder 1 , Kyle Falke 1 , Jaime C. Grunlan 1
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2016-12-08 00:00:00 , DOI: 10.1021/acsami.6b12937 Yixuan Song 1 , David A. Hagen 1 , Shuang Qin 1 , Kevin M. Holder 1 , Kyle Falke 1 , Jaime C. Grunlan 1
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Layer-by-layer (LbL) assembled polymer–clay multilayer thin films are known to provide transparent and flexible gas barrier. In an effort to further lower the oxygen transmission rate (OTR) of these nanobrick wall thin films, sodium chloride was introduced into montmorillonite (MMT) suspension as an “indifferent electrolyte”. At pH 6.5 the amphoteric edge sites of MMT have a neutral net charge, and a moderate concentration of NaCl effectively shields the charge from neighboring platelets, allowing van der Waals forces to attract the edges to one another. This edge-to-edge bonding creates a much more tortuous path for diffusing oxygen molecules. An eight-bilayer (BL) polyethylenimine (PEI)/MMT multilayer coating (∼50 nm thick), assembled with 5 mM NaCl in the aqueous clay suspension, exhibited an order of magnitude reduction in oxygen permeability (∼4 × 10–20 cm3·cm/(cm2·Pa·s)) relative to its salt-free counterpart. This result represents the best barrier among polymer–clay bilayer systems, which is also lower than SiOx or AlxOy thin films. At higher NaCl concentration, the strong charge screening causes edge-to-face bonding among MMT nanoplatelets, which leads to misalignment in assembled films and increased OTR. This “salty-clay” strategy provides an efficient way to produce better multilayer oxygen barrier thin films by altering ionic strength of the MMT suspension. This simple modification reduces the number of layers necessary for high gas barrier, potentially making these multilayer films interesting for commercial packaging applications.
中文翻译：
粘土的边缘电荷中和以改善多层纳米砖壁薄膜中的氧气阻隔性
众所周知，逐层（LbL）组装的聚合物-粘土多层薄膜可提供透明而灵活的阻气层。为了进一步降低这些纳米砖壁薄膜的氧气透过率（OTR），将氯化钠作为“无差异电解质”引入了蒙脱石（MMT）悬浮液中。在pH值为6.5时，MMT的两性边缘位置具有中性净电荷，适度的NaCl浓度可有效地将电荷与相邻的血小板隔离开，从而使范德华力将边缘彼此吸引。这种边缘到边缘的结合为扩散氧分子创造了一条更为曲折的路径。一种八双层（BL）聚乙烯亚胺（PEI）/ MMT多层涂层（约50 nm厚），在水性粘土悬浮液中与5 mM NaCl组装在一起，– 20 cm 3 ·cm /（cm 2 ·Pa·s））。该结果代表了聚合物-粘土双层系统中的最佳屏障，该屏障也低于SiO x或Al x O y薄膜。在较高的NaCl浓度下，强电荷筛选会导致MMT纳米片之间的边对面键合，从而导致组装膜中的未对准和OTR的增加。这种“咸黏土”策略通过改变MMT悬浮液的离子强度，提供了一种生产更好的多层隔氧薄膜的有效方法。这种简单的修改减少了高阻气层所需的层数，从而潜在地使这些多层膜对于商业包装应用变得令人感兴趣。
更新日期：2016-12-08
中文翻译：
粘土的边缘电荷中和以改善多层纳米砖壁薄膜中的氧气阻隔性
众所周知，逐层（LbL）组装的聚合物-粘土多层薄膜可提供透明而灵活的阻气层。为了进一步降低这些纳米砖壁薄膜的氧气透过率（OTR），将氯化钠作为“无差异电解质”引入了蒙脱石（MMT）悬浮液中。在pH值为6.5时，MMT的两性边缘位置具有中性净电荷，适度的NaCl浓度可有效地将电荷与相邻的血小板隔离开，从而使范德华力将边缘彼此吸引。这种边缘到边缘的结合为扩散氧分子创造了一条更为曲折的路径。一种八双层（BL）聚乙烯亚胺（PEI）/ MMT多层涂层（约50 nm厚），在水性粘土悬浮液中与5 mM NaCl组装在一起，– 20 cm 3 ·cm /（cm 2 ·Pa·s））。该结果代表了聚合物-粘土双层系统中的最佳屏障，该屏障也低于SiO x或Al x O y薄膜。在较高的NaCl浓度下，强电荷筛选会导致MMT纳米片之间的边对面键合，从而导致组装膜中的未对准和OTR的增加。这种“咸黏土”策略通过改变MMT悬浮液的离子强度，提供了一种生产更好的多层隔氧薄膜的有效方法。这种简单的修改减少了高阻气层所需的层数，从而潜在地使这些多层膜对于商业包装应用变得令人感兴趣。
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