Research On UV Curable Imidazolium Based Antibacterial Polymers

Antibacterial polymers have attracted considerable interests due to the outstandingantibacterial ability and many other unique properties, such as high chemical stability,long-term antibacterial ability, and low residual toxicity. Various efforts have beenmade to develop the polymers with antimicrobial function. This study focus onmolecular design and synthesis of UV curable imidazolium based antibacterialpolymers.Firstly, four UV curable quaternary ammonium salt monomers such asC4ImMA-Br, C6ImMA-Br, C8ImMA-Br, C12ImMA-Br, were synthesized with thehelp of molecular design. The synthesized monomers were characterized by MS, FT-IR,1H-NMR. The reaction conditions for the synthesis of C4ImMA-Br and C12ImMA-Brwere dicussed and it was found that the optimal reaction conditions of C4ImMA-Br is at40℃~50℃for24h, and that of C12ImMA-Br is at50℃~60℃for28h.Compared of the thermal heating, ultrasonic-assisted method significantly enhances theefficiency that reaches the same yields while at room temperature for2h.Secondly, it was found that the solubility of monomers changes with polarity ofsolvents and as a result, methanol was chose as the diluted solvents in UV curing. TheUV sensitivity of the four monomers was characterized by FT-IR, DPC and UV. Theresults point out that all the four monomers have quite good UV-sensitive properties:90%of heat flow of the four monomers was completed within1.5min, and the peak heatflow was appeared at around50sec. The efficiency of ultraviolet absorbance ofmonomers was descended with the increase of the number of carbon atoms in thesubstituted alkyl chain.Thirdly, the bactericidal activities of the four new quaternary ammonium salt(QAS) monomers were evaluated by determining MBC (Minimum BactericidalConcentration) values against E. coli. The MBC values of C4ImMA-Br andC6ImMA-Br was higher than1mg/mL, while the MBC value of C8ImMA-Br was0.625mg/mL and the MBC value of C12ImMA-Br was even less than0.2mg/mL. Theantibacterial activity of QAS monomers increases with the increase of the length ofalkyl chain. The longer was the alkyl chain, the stronger the hydrophobic interactionbecame between the alkyl chain and cytoplasmic membrane, and thus the higherbactericidal ability. In addition, the bactericidal activities of the polymerized thin layercoatings were evaluated by inhibitory zone diameters against E. coli. The diameter ofinhibitory zone of four bactericidal coatings decreases with the length of alkyl chain,which keeps good accordance with the MBC of the four monomers.