Amphiphilic block and statistical siloxane copolymers with antimicrobial activity

Statistical and block all-siloxane copolymers containing quaternary ammonium salt (QAS) groups with biocidal activity as lateral substituents were synthesized as models for the study of the effect of the arrangement of the QAS groups in the copolymer chain on their antimicrobial activity. The bioactive siloxane unit was [3-n-octyldimethylammoniopropyl]methylsiloxane, and the neutral unit was dimethylsiloxane. The copolymers also contained siloxane units with unreacted precursor 3-chloropropyl or 3-bromopropyl groups. A small number of units containing highly hydrophilic 3-(3-hydroxypropyl-dimethylammonio)propyl groups were introduced to increase the solubility of the copolymers in water. The bioactive and bioneutral units were arranged in the polymer chain either in blocks or in statistical order. The block copolymers differed in the number and length of segments. The copolymers were obtained by the quaternization of tertiary amines by chloropropyl or bromopropyl groups attached to polysiloxane chains. The arrangement of the bioactive groups was controlled by the arrangement of the halogenopropyl groups in the bioactive copolymer precursor. All model siloxane copolymers showed high bactericidal activity in a water solution toward the gram-negative bacteria Escherichia coli and the gram-positive bacteria Staphylococcus aureus. However, no essential differences in the activities of the copolymers with block and statistical arrangements of units were detected. (C) 2003 Wiley Periodicals, Inc.