Thermoresponsive polymer desiccants for water harvesting

Abstract

Atmospheric water is a ubiquitous yet underutilised source of potable water. Polymeric desiccants are a particularly promising candidate for atmospheric water harvesting given their adaptability and scalability. However, the relative nascency of the field leaves many classes of polymers yet unexplored. This thesis details efforts into developing novel polymeric desiccants for atmospheric water harvesting while establishing frameworks for their rational design. The focus is primarily on thermoresponsive polymers, a particularly useful class of materials enabling the low energy release of sorbed water. Despite this property these materials have been largely overlooked for water harvesting applications. In Chapter 1, the current literature in atmospheric water harvesting is described, giving context to the experimental work reported within. In Chapter 2, a thermoresponsive copolymer library was synthesised to examine how differences in composition, crosslinker density and crosslinker length affected water harvesting properties. These insights into the relationship between polymer structure and water harvesting properties lay the groundwork for future rational design. Chapter 3 details the development of a novel desiccant utilising L-arginine post-functionalisation of a thermoresponsive polymer. The resulting desiccant was highly hygroscopic while retaining its thermoresponsive properties. The kinetics of its water harvesting allowed for rapid harvesting cycles and increased yield. Finally, Chapter 4 presents improved desiccants culminating from insights gained in the preceding chapters. The use of microgel structures and creatine functionalisation further improved water harvesting kinetics. In addition to highlighting the potential of microgels as a class of polymeric desiccants, these materials outperform many of those in existing literature. Show more