Polymers are an integral part of all aspects of sustainable energy solutions. Everything from wind turbine blades to biomass is made up of polymers, the high molecularweight macromolecules that are a ubiquitous part of our lives. This chapter presents the basics of polymer chemistry with a few examples in the realm of CO2 separation (Section More depth is provided in the context of the composite polymers used in the fabrication of wind turbine blades. Additional applications of polymer chemistry in sustainable energy are introduced in later chapters in the context of fuel cells (Chapter 6), solar photovoltaics (Chapter 7), and biomass (Chapter 8).