Transport properties of drug precursor molecules in nanoporous polymers

Abstract

This PhD thesis is framed in the European project CUSTOM, which aims to develop a small size device able to detect drug precursors molecules in the air, even when they are just in traces. The project is part of the European strategies to fight the illegal drug trafficking, that is a serious problem experienced in all countries worldwide. Recently, in fact, drug traffickers smuggle drug precursor molecules, that is molecules that are converted into the final product through chemical processes, once arrived in the country of destination. For this reason many efforts are making to detect the presence of precursors in very low concentrations using dedicated sensors. The low concentration of these kind of molecules requires that the sampling techniques concentrate as much as possible the target analytes. For this purpose, syndiotactic polystyrene (sPS), a cheap and commercial thermoplastic polymer, can be a good choice: it can be achieved in highly porous crystalline morphologies (aerogels) able to maximize molecules sorption and desorption kinetics thanks to their high surface area1. High-porosity sPS aerogels can be obtained by supercritical CO2 extraction of the solvent present in sPS physical gels (gels in which the junctions between polymer chains consist of crystalline regions). Furthermore, sPS crystalline aerogels can be achieved in two different nanoporous crystal forms, delta (δ) and epsilon (ε). These two phases present well-defined empty spaces distribute into the crystal lattice as cavities (δ form) or channels (ε form). Both these two crystalline forms are able to rapidly absorb volatile organic compounds (VOCs), mainly halogenated or aromatic hydrocarbons, from water and air also when present at very low concentrations2. This polymer, combined with a suitable detection system for these precursor molecules, could be a winning choice for the purposes of the CUSTOM project. Within the project, our tasks and objectives are to evaluate the capacity and the effectiveness of the polymer to absorb some target drug precursors, to validate the air sampling module which will be implemented in the device and, finally, to establish if and how the presence of some common pollutants in the air could affect the sorption of the selected precursors. [edited by author]