Synthesis of polyamide 6 with aramid units by combination of anionic ring-opening and condensation reactions

Polyamides with different percentages of aromatic/aliphatic units and molar masses were synthesized in a one-step bulk copolymerization of ε-caprolactam and ethyl 4-aminobenzoate at 140 °C keeping the same experimental conditions basically used for the synthesis of polyamides by anionic ring opening polymerization (AROP). Copolyamides were characterized by NMR spectroscopy, size exclusion chromatography and thermo-mechanical analysis (DSC, TGA and DMA). This methodology, combining simultaneous anionic ring-opening and condensation reactions, affords a new route to introduce aromatic amides into an aliphatic polyamide backbone and tune its properties. Modified polyamides 6 (PA6) obtained from ε-caprolactam by an activated monomer mechanism and containing up to 17% mol of aromatic moiety were prepared. The new materials exhibited in particular high thermal stability and high glass transition temperature up to 79 °C.