Poly(ionic liquid) stabilizers and new synthetic approaches The main focus of the present thesis was to investigate the stabilization ability of poly(ionic liquid)s (PILs) in several examples as well as develop novel chemical structures and synthetic routes of PILs. The performed research can be specifically divided into three parts that include synthesis and application of hybrid material composed of PIL and cellulose nanofibers (CNFs) thiazolium containing PILs and main chain imidazolium type PILs. In the first chapter a vinylimidazolium type IL was polymerized in water in the presence of CNFs resulting in the in situ electrostatic grafting of polymeric chains onto the surface of CNFs. The synthesized hybrid material merged advantages of its two components that is superior mechanical strength of CNFs and anion dependent solution properties of PILs. In contrast to unmodified CNFs the hybrid could be stabilized and processed in organic solvents enabling its application as reinforcing agent for porous polyelectrolyte membranes. In the second part PILs and ionic polymers containing two types of thiazolium repeating units were synthesized. Such polymers displayed counterion dependent thermal stability and solubility in organic solvents of various dielectric constants. This new class of PILs was tested as stabilizers and phase transfer agents for carbon nanotubes in aqueous and organic media and as binder materials to disperse electroactive powders and carbon additives in solid electrode in lithium ion batteries. The incorporation of S and N atoms into the polymeric structures make such PILs also potential precursors for S N co doped carbons. In the last chapter reactants originating from biomass were successfully harnessed to synthesize main chain imidazolium type PILs. An imidazolium type diester IL obtained via a modified Debus Radziszewski reaction underwent transesterification with diol in a polycondensation reaction. This yielded a polyester type PIL which CO2 sorption properties were investigated. In the next step the modified Debus Radziszewski reaction was further applied to synthesize main chain PILs according to a convenient one step protocol using water as a green solvent and simple organic molecules as reagents. Depending on the structure of the employed diamine the synthesized PILs after anion exchange showed superior thermal stability with unusually high carbonization yields. Overall the outcome of these studies will actively contribute to the current research on PILs by introducing novel PIL chemical structures improved synthetic routes and new examples of stabilized materials. The synthesis of main chain imidazolium type PILs by a modified Debus Radziszewski reaction is of a special interest for the future work on porous ionic liquid networks as well as colloidal PIL nanoparticles.