Antimicrobial-modified sulfite pulps prepared by in situ copolymerization

Grafting guanidine polymer (PHGH) onto cellulose fibers was conducted via in situ free-radical polymerization using ceric ammonium nitrate (CAN) as an initiator. The optimum reaction conditions were obtained, under which the grafting percentage and the grafting efficiency reached over 20% and 50%, respectively. Atomic force microscopy (AFM) images revealed that the grafted polymer tended to form grains with diameters ranging from 60 to 200 nm. AFM also enabled us to identify the location of the grafts on the surfaces of cellulose fibers by the measurements of the adhesion and attraction forces between a colloid probe and the samples. The cellulose fibers were rendered antimicrobial in the presence of 1.0% (wt) grafted polymer, and an excellent antimicrobial activity (over 99% inhibition) toward Escherichia coli was achieved. The AFM results also demonstrated that the antimicrobial mechanism of PHGH is to destroy the membrane of the cells.