Water Content of Polyelectrolyte Multilayer Films Measured by Quartz Crystal Microbalance and Deuterium Oxide Exchange

Abstract

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.

Induction heating induced self-healing of nanocomposites based on surface-functionalized cationic iron oxide particles and polyelectrolytes

“…This water affinity of polyelectrolytes is well known and studied extensively, as the water content governs a plethora of properties such as mechanical strength, rigidity and ion conductivity. 59–62 Therefore, storage conditions such as humidity and temperature have to be controlled.…”

“…This water affinity of polyelectrolytes is well known and studied extensively, as the water content governs a plethora of properties such as mechanical strength, rigidity and ion conductivity. [59][60][61][62] Therefore, storage conditions such as humidity and temperature have to be controlled. The observed increase of the glass transition temperature with increasing proportion of ionic species is below the rule of mixture.…”

Current Opportunities and Challenges in Biopolymer Thin Film Analysis—Determination of Film Thickness

“…The (Δf/n) water is then be used to determine the water concentration in the film. The method has recently been used for determination of water content in polyelectrolyte multilayers (Kittle et al, 2021). The film thickness affects the amount of bound water and needs to be known to enable direct quantitative comparison.…”

Strategies for the Accurate Measurement of the Resonance Frequency in QCM-D Systems via Low-Cost Digital Techniques

“…Focusing on the direct resonance frequency measurement, a more versatile widespread technique is the Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]; this technique is based on the simultaneous measurement of the sensor resonance frequency and of its dissipation factor (i.e., the reciprocal of the quartz quality factor) during a transient response triggered by short electric excitations.…”