Ionic Liquid-Grafted Polyamide 6 by Radiation-Induced Grafting: New Strategy To Prepare Covalently Bonded Ion-Containing Polymers and their Application as Functional Fibers

Ion-containing polymers are of great importance for its unique structure and properties. An ion-containing polyamide 6 (PA6) was prepared by grafting an ionic liquid, 1-vinyl-3-butyl imidazole chloride [VBIM][Cl], onto the main chain of PA6 using radiation-induced grafting. The grafted ions on the PA6 main chain significantly influenced the structure and properties of the PA6 matrix. The ions form nanoscale aggregations without inducing further microphase separation. Acting as a physical "cross-linking point," each aggregation enhanced inter/intrachain interactions, which increased the viscosity, storage modulus, and relaxation time and reduced the ability of PA6 to crystallize. However, the bulky cations of the grafted ionic liquid can also be seen as "spacers," which enlarge the distance among chains and reduce the strength of the hydrogen bonds inherently existing in the PA6 matrix. The "cross-linking points" and "spacers" of ions as well as the hydrogen bonds of PA6 take effect collectively in the system. Moreover, the ion-containing PA6 retains good melt processability compared with PA6, despite increased viscosity, and can be easily melt-spun into fibers. Fibers prepared from ion-containing PA6 showed improved mechanical properties and antistatic performance and exhibited the expected antibacterial properties, especially with regard to Escherichia coli. Inspiringly, covalently bonding ions to the PA6 main chain offers a new strategy for fabricating functional fibers with permanent antistatic and antibacterial properties.