Method for preparing polyamide by anion ring-opening polymerization and polyamide prepared thereby

A method for preparing a polyamide by an anionic polymerization reaction, said method comprising:

• subjecting a lactam compound to an anionic ring-opening polymerization to prepare the polyamide, in the presence of, based on 100 parts by weight of a total weight of the lactam compound, 0.01 parts by weight to 20 parts by weight of an alkali metal as an initiator, 0.3 parts by weight to 10 parts by weight of a molecular weight controller, and 0.002 parts by weight to 1.0 part by weight of carbon dioxide as an activator,
• wherein the molecular weight controller comprises one or more selected from the group consisting of a urea compound, and a di-urea compound,
• wherein the polyamide has a polydispersity index (PDI) of 2.5 or less, and
• wherein the anionic polymerization reaction is carried out in the absence of a solvent.