The book “POSS Nanocomposite Membranes: Synthesis and Gas Separation Studies” was well thought about knitting several broad disciplines of nanocomposites in mind. A glance through the pages of science and engineering literature shows that the use of nanocomposites for emerging technologies represents one of the most active research area and development the fields of chemistry, physics, life sciences, and related technologies. Book concept is based as much on the serendipity of these new ideas as on need to offer blueprints for the design of different membranes for emerging technologies. This book focuses on synthesis of polyamide, polyimide, poly(urethane-imide), and transport properties of N2, O2, CO2 gases and their possible divergent applications. This book comprises 6 chapters. Chapter 1 provides introduction of new developments of POSS and POSS nanocomposites. Chapter 3 describes the effect of POSS on polyamides. Chapter 4 deals the synthesis and characterization of Polyimides. Chapter 5 presents the synthesis of poly(urethane-imide)-POSS with various hard and soft segments. Chapter 6 represents the gas transport properties of N2, O2 CO2 by constant volume/variable pressure.