Synthesis of ammonium bisphosphonate monomers and polymers

Ammonium bisdiethylphosphonate acrylate and methacrylate monomers were synthesized by an aza-Michael addition of 3-aminopropanol across the double bond of bisdiethylphosphonate, followed by acylation with (meth)acryloyl chloride. Free radical copolymerizations of the monomers with an acrylate-functional poly(ethylene oxide) (PEO) macromonomer produced graft copolymers. Quantitative deprotection of the alkylphosphonate groups, then adjustment of the pH to 7.74 ± 0.03, yielded graft copolymers with zwitterionic ammonium bisphosphonate backbones and PEO grafts. Copolymerization kinetic studies showed that the ammonium bisdiethylphosphonate methacrylate incorporated into the copolymers with PEO-acrylate well, but that the corresponding acrylate monomer reacted too slowly. The zwitterionic copolymers spontaneously assembled into aggregates in aqueous media.