**Abstract**

As much of the concern is being placed on metal-free polymerization, carbenes are attracting researcher attention. Besides their impact on organic synthesis, they played an integral role in several types of polymerization. This unique class of organocatalyst revives the preparation of polymeric materials that possess functional groups at each carbon atom on the polymer chain, which was hardly reached by conventional methods. This chapter will concern with the contribution of N-heterocyclic carbenes (NHCs) in the preparation of functional polymers from diversified monomers. Also, will discuss the advantages of N-heterocyclic carbenes in some conventional polymerization such as ring-opening and step-growth polymerizations along with the direct zwitterionic polymerization.

**Keywords:** ring-opening polymerization, step-growth polymerization, zwitterionic polymerization, metal-free polymerization, heterocyclic carbenes
