Thermophysical behaviour and applications of crosslinked poly(ionic liquid)s

Ionic liquids (ILs) were discovered in 1914 by Paul Walden when he synthesized ethylammonium nitrate, which was the first salt to be liquid at room temperature. After this point the field of ILs enjoyed a surge in popularity. The main reasons for this interest came from the physical and chemical properties of ionic liquids, including high chemical, thermal and electric stability, negligible vapour pressure, very good dissolution properties and highly tunable configuration, respectively. Based on these properties, ILs with applications in catalysis, solvation, and electrochemistry were developed. At the turn of the 20th century, the first paper published on polymerizable ILs (PILs) appeared. This opened up a new research direction that has just recently started getting more attention. This thesis focuses on presenting the synthesis, characterisation and potential applications of novel stimuli-responsive materials based on PILs and crosslinked PILs. Chapter 1 will offer a brief overview of the field of ILs and PILs in particular, and Chapter 2 will discuss possible application of such materials in microfluidic devices. Chapter 3 will describe the synthesis of temperature-responsive crosslinked PIL hydrogels which serve as a host matrix for a linear photo-responsive poly(Nisopropylacrylamide) based polymer. Moreover, the resulting composite stimuli responsive material will be characterized to determine its response to temperature, light and salt concentration, respectively. Chapter 4 focuses on the integration of the temperature-responsive PIL matrix in a microfluidic device as a temperature controlled valve, and Chapter 5 will demonstrate the printing of such materials using Direct Laser Writing technologies. Chapter 6 and 7 will focus on the synthesis and thermal characterization of a novel crosslinked cholinium PIL hydrogel and its integration in paper-based microfluidic devices as passive pumps (Chapter 7). Chapter 8 describes future work in the area of PILs and PIL hydrogels