Chemical structures that interact with multivalent cations in solution and with surfaces containing multivalent cations are useful for manipulation of these systems. Polyphosphates and pyrophosphate, for example, have been used as builders in laundry and dish formulations to control calcium and in drilling muds to prevent precipitation. They have also been used in the oral care industry to help control tartar and reduce the thickness of the pellicle layer on teeth resulting in a slick tooth feel. Similarly, bisphosphonates, and hydroxy-bisphosphonates are active components in osteoporosis pharmaceuticals due to their strong interaction with calcium hydroxy apatite surfaces and are also used as crystal growth inhibitors in dishwashing liquids and boiler systems. Each of these examples suffer from an inherent limitation. Polyphosphates are prone to degradation over time in aqueous solutions at all pH's, ultimately leading to an increase in ortho phosphate in solution. Polyphosphate salts are also quite anionic in nature and are not soluble in non-polar organic systems. Polyphosphates are, however, generally safe for consumption and find use in different food products. Bisphosphonates and hydroxy-bisphosphonates are, conversely, stable in water for long periods of time, and can, depending upon the nature of the organic group attached to the bisphosphonate carbon, be made quite soluble in organic systems. Bisphosphonates, however, are bone active and hence cannot be used in foods or other systems where they might be accidently consumed due to their potent pharmacology. Polymers containing bisphosphonates of sufficient molecular weight to not pass through the intestinal wall would likely not be bone active, however any low molecular weight residual monomers or oligomers that could pass through the intestinal wall make the use of such polymers prohibitive in potential consumable contexts. In addition, since bisphosphonates do not break down readily, their activity can persist in the environment after use.
Therefore, a need still exists for a method of making a phosphate-like composition that interacts with multivalent cations in solution and with surfaces containing multivalent cations, that does not easily degrade, and that is safe for human consumption.