Synthesis of novel polymers of intrinsic microporosity for gas and vapour adsorption

Abstract

Polymers of intrinsic microporosity (PIMs) are a class of highly porous polymeric materials, within which the microporosity originates from the inability of the rigid and contorted polymeric chains to pack efficiently. PIMs exhibit outstanding solution processability, large surface areas and great structural tunability, which makes them promising materials for a range of applications, such as gas separation, catalysis and sensors. Furthermore, their highly porous nature, along with gas separation performances, makes PIMs excellent materials for gas adsorption applications, which includes the capturing and storage of CO2, and the deactivation of chemical warfare agents (CWAs), as they can efficiently store a significant volume of adsorbate in their pores, which are flexible due to the lack of a covalent network structure. Additionally, their macromolecular structures can be tailored to show special selectivity towards the target gases.

The project described in this thesis explored ways to further enhance the gas adsorption properties of PIMs, via three approaches. First, the incorporation of additional basic, and nucleophilic functionality onto PIMs was investigated to induce additional acid-base interactions with acidic gases such as CO2, and the potential catalytic reactivity towards electrophilic compounds such as organophosphorus-based CWAs. A PIM containing pyridine units was synthesised, and further functionalised with amidoxime groups. The effect of the basic and nucleophilic functional groups incorporation on PIMs were studied by comparing their polymer properties, and performances in areas such as CO2 adsorption, CWA deactivation, and gas separation of the synthesised polymers against that of related PIM-1 and AO-PIM-1. Secondly, the synthesis of the extremely bulky and rigid structural unit, naphthopleiadene (NP), with in-built amine functionalities was explored to enhance the porosity of PIMs, and to increase the affinity of polar gases such as CO2 towards PIMs. Finally, the synthesis of some -CF3 containing monomers were attempted. These fluorinated PIMs were expected to minimise interactions between polymeric chains, thus offering the possibility of altered solubility, and reducing the impact of weak interchain interactions on the porosity, and further enhance the hydrophobicity of PIMs to increase their selectivity of the target gas molecules over water vapours.