Kittle Joshua, Levin Jacob, Levin Nestor
Department of Chemistry, United States Air Force Academy, 2355 Fairchild Drive, Colorado Springs, CO 80840, USA.
Sensors (Basel). 2021 Jan 24;21(3):771. doi: 10.3390/s21030771.
Water content of natural and synthetic, thin, polymer films is of considerable interest to a variety of fields because it governs properties such as ion conductivity, rigidity, porosity, and mechanical strength. Measuring thin film water content typically requires either complicated and expensive instrumentation or use of multiple instrumental techniques. However, because a quartz crystal microbalance (QCM) is sensitive to changes in mass and viscosity, deuterated solvent exchange has emerged as a simple, single-instrument, in situ method to quantify thin film water content. Relatively few studies, though, have employed this technique to measure water content of polyelectrolyte multilayers formed by layer-by-layer (LbL) assembly. In this work, poly (allyl amine) (PAH) and poly (styrene sulfonate) (PSS) films of up to nine layers were formed and the water content for each layer was measured via QCM with deuterium oxide exchange. The well-characterized nature of PAH/PSS films facilitated comparisons of the technique used in this work to other instrumental methods. Water content results showed good agreement with the literature and good precision for hydrated films thicker than 20 nm. Collectively, this work highlights the utility, repeatability, and limitations of this deuterated exchange technique in measuring the solvent content of thin films.
天然和合成的薄聚合物膜的含水量在多个领域备受关注,因为它决定了诸如离子电导率、刚性、孔隙率和机械强度等性质。测量薄膜含水量通常需要复杂且昂贵的仪器设备,或者使用多种仪器技术。然而,由于石英晶体微天平(QCM)对质量和粘度的变化敏感,氘代溶剂交换已成为一种简单的、单仪器原位方法来量化薄膜含水量。不过,相对较少的研究采用这种技术来测量通过逐层(LbL)组装形成的聚电解质多层膜的含水量。在这项工作中,形成了多达九层的聚(烯丙基胺)(PAH)和聚(苯乙烯磺酸盐)(PSS)膜,并通过氧化氘交换的QCM测量了每层的含水量。PAH/PSS膜的特性明确,便于将本工作中使用的技术与其他仪器方法进行比较。含水量结果与文献显示出良好的一致性,对于厚度超过20nm的水合膜具有良好的精度。总体而言,这项工作突出了这种氘代交换技术在测量薄膜溶剂含量方面的实用性、可重复性和局限性。