Solution polymerization

Catalysis

Polymerization

Polymer chemistry

Chain transfer

Bulk polymerization

Anionic addition polymerization

Polymer

Organic chemistry

Radical polymerization

Caprolactam

Chemistry

Molar mass distribution

Monomer

Bifunctional

Polymer Journal

To obtain high molecular weight nylon 6, the anionic polymerization of ε-caprolactam was investigated in terms of water content in monomer and concentration of catalyst (Grignard reagent; ethyl magnesium bromide) and chain initiator (monofunctional; N-acetyl-ε-caprolactam or bifunctional; N,N′-adipoyl-bis-ε-caprolactam). The weight average molecular weight, Mw=7.0×105 (the intrinsic viscosity; [η]=11.2) was obtained using the monofunctional chain initiator, and Mw=9.5×105 ([η]=14.1) was found using the bifunctional chain initiator under the following conditions: water content, 0.013 mol%; concentration of catalyst, 0.1 mol%; concentration of chain initiator, 0.03 mol% (monofunctional), 0.015 mol% (bifunctional); polymerization temperature, 150°C. In the present study, the molecular weight of the polymer is governed by quantities of active molecular chains. Since water mainly terminates the propagation of molecular chains, minimizing water content in ε-caprolactam is indispensable to maximizing the molecular weight of the polymer.

Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam