Abstract: The reaction of compounds of the formula:X.sub.2 O.sub.3 P CHY CZ.sub.2where Y and each Z are each H, PO.sub.3 X.sub.2, SO.sub.3 X or CO.sub.2 X (e.g. vinyl phosphonic acid or vinylidene diphosphonic acid) with hypophosphorous acid in the presence of free radicals provides novel compounds X.sub.2 O.sub.3 PCHYCZ.sub.2 PO.sub.2 XH which react with monomers such as vinyl sulphonate, vinyl phosphonate, vinylidene diphosphonate and acrylic acid to form telomers useful for scale inhibition, especially barium scale in oil wells. The polymers show better absorption to rock than PVSA and better thermal stability than random copolymers containing equivalent phosphorus.

Abstract: Phosphonic acid polymers are prepared from di- or polyphosphonic acids having one or more unsaturated C.dbd.C bonds (e.g. vinylidene-1,1-diphosphonic acid), either as homopolymers or as higher polymers with at least one further compound having unsaturated C.dbd.C bonds (e.g. acrylic acid). The polymers can be used as, or in connection with, flame-retardants, corrosion inhibitors, coatings, cements and ion exchange resins.