Increasing QCM sensitivity based on high molecular weight porous polymer films

Abstract

High molecular weight porous poly(methyl methacrylate) (PMMA) films sensitive to water vapor were produced on a QCM crystal by first dip coating the quartz crystal into polymer solutions containing both PMMA and poly(ethylene oxide) (PEO). After drying, these films were leached with water to remove the PEO which created porous PMMA films. The most sensitive film to water vapor contained both high molecular weight PMMA and PEO as film components. Porous PMMA films made from high molecular weights of both components comprising PMMA/PEO blended polymers had higher water vapor sensitivities. The molecular weight of the PMMA in a nonporous film only had a small effect on its water vapor sensitivity. The approach used in this research is a general and can be used to increase the sensitivity of gas sensors in which the polymer that is leached by water (or other solvent) contains a functional group sensitive to a targeted volatile species.