Surface energy measurements are often used to investigate interfacial properties including adhesion, wettability, specific interactions with other molecules, and coating performance. Inverse gas chromatography (iGC) provides a facile method to measure the surface properties of fibrous and particulate materials; in particular, it has been recently used to study the diffusion and permeability of gases through polymer coatings on silica beads. However, measurement of 2D materials (either as monoliths or as thin coatings or films) is still being developed and demonstrated. Here, we introduce a new method to measure total surface energy and its dispersive and specific constituents for polymer thin films on silicon wafers, including poly (methyl methacrylate) (PMMA), polyacrylic acid (PAA) and polyethylene glycol (PEO) thin films through layer-by-layer (LbL) approaches. Through the use of hydrogen bonds, a hydrogen-bond-accepting polymer (PEO) can be incorporated with a hydrogen-bond-donating polymer (PAA). We optimized the measurement in a 2D film cell module by troubleshooting unique issues, such as the control of concentration range of probe gas injection, which was found to be the critical factor to obtaining reproducible and accurate results. This work shows promise for a new analyzing tool for applications, such as nanocomposites and membranes.

Inverse gas chromatography (iGC) as an effective tool for measuring surface properties of polymer thin films

ACS Spring 2022

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