N-chlorinated poly(N-isopropylacrylamide) microgels

The treatment of poly(N-isopropylacrylamide) (PNIPAM) microgels with aqueous bleach (NaClO) at pH 10.5 resulted in the partial conversion of the amide hydrogen to the corresponding chloramide. N-Chlorinated microgels poly(NIPAM-co-NIPAMCl) are more hydrophobic than the parent PNIPAM microgels. Thus, the volume phase transition temperature decreases with increasing chlorination. During chlorination, the microgels coagulate once they undergo a volume phase transition. The chlorination reaction stops once the microgels dehydrate and coagulate, presumably as a result of the decreased diffusion rate of the ClO(-) anion into the microgels. The microgels are reversibly dechlorinated by glutathione (GSH), first giving PNIPAM shell + poly(NIPAM-co-NIPAMCl) core microgels. Because GSH is an important redox actor in biological cells, this work suggests that chlorinated microgels may be employed to deliver active chlorine to targeted cells.