Tips for Selecting Polymeric Ethanol-sensing Materials: Detection Mecha- nisms and Sensing Materials K. M. E. Stewart and A. Penlidis IPR Symposium (May 2015), Department of Chemical Engineering, University of Waterloo, Wa- terloo N2L 3G1 Canada Driving under the influence of alcohol (ethanol) is a major problem and results in numer- ous casualties and deaths each year (Solomon et al., 2012). Therefore, reliable monitoring of blood alcohol levels is needed. Currently, breathalyzers, which measure ethanol in the breath, are used; however, their frequency of use (typically sporadic spot checks) is limited. Also, inter- lock ignition systems are cumbersome and a distraction to the driver. The goal is to create a transdermal ethanol sensor that is less distracting to the driver and autolocks a vehicle’s ignition when ethanol is detected from the driver. This goal results in a set of operating specifications that restrict the type of sensing mate- rials used in such a sensor. For example, transdermal ethanol sensors must be very sensitive to ethanol and very selective due to the amount of other volatile organic compounds (VOCs) that are also emitted from the skin. Additionally, for an in-vehicle sensor, a polymeric sensing mater- ial must have a high glass transition temperature, since the internal temperature of a vehicle can range between -40°C and 60°C (Null, 2003). These constraints will aid in selecting appropriate sensing materials for ethanol and the target application. When choosing polymeric sensing materials, it is important to look at how their function- al groups and side chains will interact with the target analyte (in this case, ethanol). Determining the mechanisms by which the target analyte is likely to interact with a sensing material will help narrow down potential sensing materials for ethanol. For example, ethanol is a polar molecule with a hydrogen attached to an oxygen (contains an alcohol functional group); therefore, ethanol is able to hydrogen bond. Thus, a corresponding sensing material that would show affinity to ethanol should also be polar and ideally be able to hydrogen bond. Polymers that fall into this category are, for example, polymers containing alcohols, amines, and carboxylic acids. Choosing a polar polymer for ethanol does not considerably narrow down the choice of polymers, since many polymers are polar and also have the ability to hydrogen bond. Since ethanol is a small molecule, polymers with shorter side chains, which have the ability to pack tighter (smaller interstitial spaces between the polymer chains), may be a superior choice since the closely packed polymer chains act as a filter, keeping larger interferent molecules out of the polymer matrix. Bulky side chains may also be used, which keep larger interferents away due to steric interactions. 1