Manipulating Polymer Blend Composition Facilitates a Low-Cost, High-Fidelity Sensor for Indoor CO₂Monitoring

Carbon dioxide (CO₂) has been linked to many deleterious health effects and has thus created a need for an indoor small-scale sensor with suitable low-cost fabrication materials for adequate monitoring of CO₂. Here, a resonant mass sensor is treated with a low-cost and solution-processable polymer blend of poly(ethylene oxide) (PEO) and poly(ethyleneimine) (PEI) which facilitates a surface morphology alteration upon blending which promotes selective and significantly enhanced detection of CO₂ gas. Based on SEM, AFM, XRD, and DMA characterization techniques, we observed PEO when incorporated into PEI allowed for a physical polymer disruption of interchain amine interactions which facilitated the interaction between intrachain amines and CO₂. Due to these changes in surface morphology upon blending in PEO, there is less amorphous uniformity in the PEI and better stiffening of the overall polymer composition which allows for better diffusion of CO₂ into the material. This alteration is important for establishing fundamental models for polymer-based gas adsorption mechanisms and provides potential design rules for promoting gas adsorption capacity, selectivity against other interfering gases, and expanding detection limits for sensor applications.