A scale-bridging study of first-principles calculations and kinetic modeling has been carried out to investigate anionic and zwitterionic chain polymerizations. On the example of the industrially relevant ethyl a-cyanoacrylate, the initiation with anionic and neutral species focusing on the first stages of chain formation is studied. In the first part of our study, we use quantum chemical methods at the DFT level to study the initiation of polymerization with an anionic species (hydroxide anion), leading to anionic chain polymerization, and a neutral species (pyridine), leading to zwitterionic chain polymerization, respectively. The calculation of reaction barriers for the initiation step reveals that the addition of a hydroxide anion to a cyanoacrylate monomer is a barrier-less and strongly exothermic process whereas pyridine addition shows a significant barrier and is slightly endothermic. Subsequent calculations of the reaction energies and barriers of cyanoacrylate polymerization up to a degree of oligomerization of 5 (X-n = 5) show that both initiation reaction and subsequent addition of the next few monomers determine the reactivity and properties of cyanoacrylates. To quantify these findings we use in the second part of our study the results of the quantum chemical calculations to parametrize a kinetic study of the polymerization process of cyanoacrylates. Starting from monomers and initiators the polymerization of the cyanoacrylate and resulting molecular weight built up is simulated. The consequences of the differences in kinetic parameters of anionic and zwitterionic mechanisms on molecular weights and polymer properties are discussed.