Eco-Friendly Leather: Synthesis and Properties of Polyionic Liquids Containing Amines as Tanning Agents

A couple of polyionic liquids (PILs) containing amines, including primary amine in p(acrylamide–methacrylic acid–methylimidazolium chloride) (PILs-PA) and quaternary ammonium in p(methacrylamidopropyl trimethylammonium chloride–methacrylic acid–methylimidazolium chloride) (PILs-QA), were synthesized by free radical polymerization. The effects of the two kinds of PILs on leather tanning, dyeing, and fatliquoring capabilities were investigated. Interestingly, the primary amine-containing PILs-PA tanned leather had a higher shrinkage temperature (84.3 °C), dye (97.4%), and fatliquoring absorption (96.8%) than the quaternary ammonium-containing PILs-QA tanned leather (82.8 °C, 95.1%, and 95.3%), respectively. X-ray photoelectron spectroscopy indicated that primary amines interact more strongly with collagen carboxyl groups, enhancing leather performance. PILs-PA tanned leather exhibited tensile and tear strengths of 18.3 MPa and 86.5 N/mm, respectively, along with an air permeability of 21771.85 mL/(cm2·h) and a water vapor permeability of 0.76 mg/(10 cm2·24 h). It also demonstrated 100% effectiveness against Staphylococcus aureus and 99.46% against Escherichia coli. These results reveal that leather tanned with primary amine-containing PILs-PA not only enhances quality and highlights the significance of amine groups in skin collagen modification but also minimizes the negative impact from chrome tanning agents, thereby yielding encouraging alternatives for cleaner manufacturing in the leather industry.