Polymeric aminomethylphosphonic acid. 1. Synthesis and properties in solution

Three water-soluble polyaminomethylphosphonic acids were obtained by radical polymerization in aqueous solution. The corresponding monomers were synthesized by different procedures. A Mannich-type reaction of diallylamine, formaldehyde, and phosphorous acid leads to diallylaminomethylphosphonic acid. Reaction of diallyl formamide and phosphorous acid results in diallylaminomethyldiphosphonic acid. Acryloylaminomethylphosphonic acid was prepared by acylation of aminomethylphosphonic acid. The diallyl compounds polymerize via cyclopolymerization, leading to polymers containing substituted pyrrolidinium rings as units of the macromolecule. Both the monomers and the polymers form zwitterionic structures in aqueous solution within a limited pH range. This was proved by 31 P-, 1H- and 13C-NMR spectroscopy, as well as by FT-IR measurements. The monomers are water-soluble without limitations, but the polymers are insoluble in a pH range near their isoelectric point, which was determined by turbidimetry and viscometry. An improvement of the solubility was achieved after the addition of inorganic salts. As expected, the monomeric and polymeric acryloyl compounds form no zwitterionic structure; both are soluble over the whole pH range investigated.