Anionic water-soluble polychloramide biocides are of
interest because,
compared to conventional cationic antimicrobial polymers, anionic
biocides are less likely to be sequestered or deactivated by contact
with non-microbial soil. Although electrostatics can prevent anionic
polymers from adsorbing on microbes, water-soluble polychloramides
appear to transfer oxidative chlorine during transient contacts between
polymer chains and microbe surfaces. The Chick–Watson model
of disinfection kinetics has been modified to account for the contributions
of polychloramide molecular weight (MW) and the polychloramide configuration
in solution estimated from the overlap concentration, C*, below which dilute polymer chains exist as discrete objects in
solution. The key assumption in the modeling was that the transfer
rate of oxidative chlorine from polychloramide chains to microbe surfaces
impacts the disinfection kinetics. Because both C* and MW are measurable, the polymer-modified Chick–Watson
(PCW) model has one less unknown parameter than the two-parameter
Chick–Watson equation. The PCW model predicts that lower MW
polymers are more effective biocides compared with high MW counterparts.
Additionally, polymers with more compressed configurations in solution
are more effective biocides. Experimental evidence supports these
conclusions. Based on the estimated time scale of bacteria/polymer
collisions compared with disinfection kinetics, arguments are made
that bacteria surfaces must be contracted many times by polychloramide
chains to achieve sufficient Cl transfer to deactivate bacteria.
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