Synthesis of aliphatic polyamide bearing fluorinated groups from ε-caprolactam and modified cyclic lysine

Abstract

Aliphatic polyamide (PA) bearing fluorinated groups was synthesized in bulk with perfluorobutyryl-substituted α-amino-ε-caprolactam and ε-caprolactam by anionic ring-opening polymerization (AROP). The fluorinated monomer was obtained by condensation between cyclic lysine (i.e. α-amino-ε-caprolactam) and perfluorobutyryl chloride. The effect of the fluorinated monomer fraction onto the AROP of ε-caprolactam was monitored by the exothermicity of this polymerization versus time. The properties and characteristics of the resulting polymers were studied by with differential scanning calorimetry, thermogravimetry, magic angle spinning NMR, FT-IR, and contact angle measurements. Polyamides bearing fluorinated groups exhibited better thermal stability than polyamide 6 (PA6) as well as a higher hydrophobic surface character as evidenced by surface tension measurements. The glass transition temperature of polyamide 6 was 53 °C and rose to 58 °C for a PA bearing fluorinated moieties, while fluorinated monomer insertion induced a decrease of the melting points from 216 to 198 °C. These copolymers displayed a maximum degradation temperature of 390 °C as compared to the 310 °C for PA6, and their surface energies decreased from 49.4 mN cm -1 (PA6 value) to 44.1 mN cm -1.