Synthesis And Characterization Of Imidazolium-type Poly(ionic Liquid)–based Functionalized Membranes

Ionic liquids are organic salts, which is composed of anion and cation. They have unique physical chemistry properties, such as low volatility, high electro conductibility and thermal stability. Ionic liquids have been widely applied in organic synthesis, environment, functional materials, energy and aerospace. Poly(ionic liquid)s are a class of polymers that combine both the novel properties of ILs and stability of polymer. Moreover, the excellent ion exchange capability enables the preparation of PILs with a variety of counter anions by polymerization of only one IL monomer and followed by ion-exchange reactions.Environmental stimuli responsive materials are a new type of functional materials with responsiveness upon the chemical and physical changes of the external environment. The environmental stimulis include temperature, pH, light, oxidation/reduction reagents and so on. The environmental stimuli responsive materials have potential application prospect in biomedical, information technology and intelligent materials.Antibacterial materials refer to a type of functional materials which can inhibit or kill bacteria. Compared with small molecule antibacterial materials, the polymer antibacterial materials are usual with high efficiency, broad spectrum and long-term antibacterial properties, good biocompatibility, which have potential applications in clinical medical and daily life.Based on the cation/anion structure and designability of poly(ionic liquid)s, stimuli responsive materials and antibacterial material are synthesized in this work. The main works are as follows:(1) Poly(ionic liquid)-based pH-responsive membranes were synthesized through anion-exchange with dye anions, which can be used in both acid and base organic and aqueous solutions. Herein we prepared an imidazolium based poly(ionic liquid)-based membranes, followed by anion exchange with anionic dyes to obtain pH-responsive membranes. The results of the study are as follows: The resultant poly(ionic liquid)-based membranes exhibit pH-responsive color and robust pH-response reversibility in both aqueous and organic solutions.(2) Amphiphilic copolymers were synthesized by anion-exchange with poly(ionic liquid)-based copolymers to control the hydrophilic /hydrophobic of the copolymers, which can self-assemble into different morphology in water. An imidazolium-type homopolymer was synthesized followed by partially anion-exchange to yield amphiphilic random copolymers. The results are as follows: The polymer side chain structure, the hydrophilic/hydrophobic of the anions, molecular weight and molecular weight distribution influence the self-assembly behavior of the polymers in solution.(3) Polymer velcro, based on host-guest interaction, was synthesized by modified host and guest groups onto the poly(ionic liquid)-based membranes surfaces, the adhesion of which is chemical and voltage-switchable. An intrinsically ionically conductive cross-linked polymer velcro membrane was synthesized, followed by modified with β-CD and Fc, respectively. The results are as follows: The obtained PIL-β-CD and PIL-Fc membranes are mechanical stability, which can adhere tightly with each other through the molecular recognition between β-CD and Fc moieties under mechanical compression. The fabricated supramolecular velcro(PIL-β-CD/PIL-Fc) exhibited strong adhesion in both air and aqueous solutions, which could be unfastened by mechanical and chemical means and refastened again under pressure. The intrinsic ionic conductivity of the PIL membranes facilitates the potential-based electrochemical switching of the adhesion.(4) The synthesis and characterization of poly(ionic liquid)-based antibacterial membranes. Imidazolium type PIL membranes were synthesized by in situ photo-cross-linking, followed by correspondingly anion-exchange to obtain effectively antimicrobial membranes. The results are as follows: The prepared membranes with different anions showed effectively antimicrobial properties against both E. coli and S. aureus. Moreover, the obtained membranes exhibited good blood compatibility, and low cytotoxicity, low adsorption of protein and recyclability.(5) The synthesis and characterization of polyanionic antibacterial membranes. The polyanionic antibacterial membranes were prepared via uv-irradiation and followed by cation-exchange with different cations, such as quaternary ammonium, imidazolium and metal cations. The results are as follows: The polyanionic membranes exhibited broad spectrum antibacterial properties, low cytotoxicity, antifouling properties and can be recycled without significant decrease of antibacterial activities.