To evaluate the influence of low molecular weight polymers synthesized through soap-free emulsion polymerization on the indicator microorganism, Micrococcus luteus, methyl methacrylate (MMA) and styrene were polymerized by using various initiators. The MMA polymer colloid was not toxic to M. luteus. High volumes of polystyrene were continuously synthesized, and low-molecular weight polystyrenes were removed from the suspension to the supernatant. During the bioassay test, as the molecular weight of the cationic polystyrene in the supernatant decreased, the inhibition zone against M. luteus grew larger. Low molecular weight cationic polystyrene was toxic to M. luteus. Hence, the supernatant containing low molecular weight cationic polystyrenes (particularly those with molecular weights below 1000 g/mol) obtained from soap-free emulsion polymerization should be treated carefully prior to its discharge to the environment. Moreover, such supernatants should be treated with more care if they are to be discharged into seas or rivers. One solution to reduce the toxicity of the supernatant against M. luteus is the addition of N-vinylacetamide monomers during polymerization.
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