POLYMERIC PHOSPHONIUM SALTS AS A NOVEL CLASS OF CATIONIC BIOCIDES .2. EFFECTS OF COUTER ANION AND MOLECULAR-WEIGHT ON ANTIBACTERIAL ACTIVITY OF POLYMERIC PHOSPHONIUM SALTS

Various poly[tributyl(4-vinylbenzyl)phosphonium salt]s with different counter anions were prepared and their antibacterial activities against Staphylococcus aureus were explored by the viable cell counting method in sterile distilled water. Antibacterial activity was found to be affected by the structure of the counter anions. The activity was low for a counter anion which tends to form a tight ion-pair with phosphonium ion, while it was high for those facilitating ionic dissociation to free ions. Furthermore, the molecular weight dependence of the antibacterial activity was investigated for poly[tributyl(4-vinylbenzyl) phosphonium chloride] with various molecular weights against S. aureus. Antibacterial activity was found to increase with molecular weight. Various copolymers were prepared in which the compositional ratio of tributyl (4-vinylbenzyl) phosphonium chloride to acrylamide, N-vinyl-2-pyrrolidone, or styrene was altered, and the effect of the positive charge density on the antibacterial activity was investigated against S. aureus. Antibacterial activity of the copolymers was much higher than that of the low-molecular-weight model compound and enhanced with the molar fraction of the phosphonium units in the copolymers.