Response of styrene-b butadiene-b styrene (SBS) deposited into quartz crystal microbalance sensor to toluene

Styrene-b Butadiene-b Styrene (SBS) is a rubbery polymer with a short relaxation time. The SBS is soluble in toluene. SBS and toluene have similar δ values according to the Hansen Solubility Parameter (HSP). Therefore, it is expected that the SBS absorb the toluene. It means that SBS can work as an active film for a gas sensor to detect the toluene. In this work, we used a Quartz Crystal Microbalance (QCM) coated with the SBS film to detect the toluene in gas. The responses of the QCM sensor with different SBS film thicknesses are investigated. The QCM with SBS film was made by depositing an SBS solution in toluene with solute-to-solvent ratios of 1%, 3%, and 5%. The spin coating method is used. The sensor response to toluene was tested by exposing the sensor to 5ppm toluene gas. The gas testing is carried out for seven cycles, where each measurement cycle is 600s and the flushing time is 500s. It is found that the sensor response to toluene is affected by the thickness of the SBS. Thicker SBS films result in higher sensitivity, however, the longer it takes to release the toluene during the flushing process.