Dynamic Measurements with Polymer Lightguides for a Selective Organic Vapor Detection

Abstract

Polymer films interact with most small gas or vapor molecules. Adsaorption layers may be formed, the small molecules may diffuse into the polymer up to an equlibrium concentration profile. If the gas or vapor partial pressure is removed the reversible process occurs, the molecules diffuse back to the surface and evaporate into the environmental atmosphere. Looking on different polymer / vapor combinations the characteristic time constants for in-and out-diffusion depend on the polarity of gas molecule and polymer, shape, size and acidity of the gas molecule ^,2. Most of the gas or vapor molecules do interact with polymer films. Therefore with respect to sensors the issue of selectivity is as important as sensitivity.