Organocatalysis provides a powerful alternative in many polymerization reactions and nowadays has become a valuable tool for polymer chemists. While organocatalysis has been largely implemented in research laboratories, its use in industrial bulk polymerization processes is still scarce. This is mostly due to the poor thermal stability of organocatalysts at temperatures (150–250 °C) usually employed for industrial polymerizations. In this lecture we will highlight the recent advances of the use of acid–base ionic mixtures in high temperatures bulk polymerization reactions. First, we will focus on the synthesis, characterization, difunctional catalytic properties, and thermal stability of these acid–base mixtures. Afterward, we will emphasize their use in step-growth and chain growth polymerization as well as in depolymerization reactions. Moreover, we will highlight also our efforts to use these catalysts as thermal/photoswitches and our efforts to exploit nature-based catalysts in polymerization reactions.