ROMP polymer-based antimicrobial films repeatedly chargeable with silver ions

Two norbornene derivatives bearing a pendant pyridyl group were prepared: the 3-(pyridin-2-yl)propyl ester of 5-norbornene-endo-2-carboxylic acid (1) and N-(pyridin-2-ylmethyl)-5-norbornene-endo-2,3-dicarboxyimide (2). Both of these compounds produced high yields of ROMP polymers, poly(1) and poly(2), with the 2nd generation Grubbs catalyst. When Ag+ ions were added to these polymer solutions, the polymer-Ag+ composites, poly(1-Ag) and poly(2-Ag), were formed quantitatively. Poly(2) and poly(2-Ag) produced films from their DMF solutions, and the latter film showed strong antimicrobial properties against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Alternatively, when the film of poly(2) was immersed in a solution of Ag+, it was able to trap the ion to give a surface-modified film [Ag/poly(2)]. The antimicrobial efficacy of [Ag/poly(2)] was the same as that of films made of poly(2-Ag), which indicated that the solid-state reaction of the film surfaces toward Ag+ ions in solution was quantitative. When the [Ag/poly(2)] film lost its biocidal effect after repeated use, the Ag+ ions could be reloaded by immersing the film in a silver ion solution, which fully restored original activity.